Пример #1
0
func rewriteToPcrel(ctxt *obj.Link, p *obj.Prog) {
	// RegTo2 is set on the instructions we insert here so they don't get
	// processed twice.
	if p.RegTo2 != 0 {
		return
	}
	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
		return
	}
	// Any Prog (aside from the above special cases) with an Addr with Name ==
	// NAME_EXTERN, NAME_STATIC or NAME_GOTREF has a CALL __x86.get_pc_thunk.cx
	// inserted before it.
	isName := func(a *obj.Addr) bool {
		if a.Sym == nil || (a.Type != obj.TYPE_MEM && a.Type != obj.TYPE_ADDR) || a.Reg != 0 {
			return false
		}
		if a.Sym.Type == obj.STLSBSS {
			return false
		}
		return a.Name == obj.NAME_EXTERN || a.Name == obj.NAME_STATIC || a.Name == obj.NAME_GOTREF
	}

	if isName(&p.From) && p.From.Type == obj.TYPE_ADDR {
		// Handle things like "MOVL $sym, (SP)" or "PUSHL $sym" by rewriting
		// to "MOVL $sym, CX; MOVL CX, (SP)" or "MOVL $sym, CX; PUSHL CX"
		// respectively.
		if p.To.Type != obj.TYPE_REG {
			q := obj.Appendp(ctxt, p)
			q.As = p.As
			q.From.Type = obj.TYPE_REG
			q.From.Reg = REG_CX
			q.To = p.To
			p.As = AMOVL
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REG_CX
			p.To.Sym = nil
			p.To.Name = obj.NAME_NONE
		}
	}

	if !isName(&p.From) && !isName(&p.To) && (p.From3 == nil || !isName(p.From3)) {
		return
	}
	q := obj.Appendp(ctxt, p)
	q.RegTo2 = 1
	r := obj.Appendp(ctxt, q)
	r.RegTo2 = 1
	q.As = obj.ACALL
	q.To.Sym = obj.Linklookup(ctxt, "__x86.get_pc_thunk.cx", 0)
	q.To.Type = obj.TYPE_MEM
	q.To.Name = obj.NAME_EXTERN
	q.To.Sym.Local = true
	r.As = p.As
	r.Scond = p.Scond
	r.From = p.From
	r.From3 = p.From3
	r.Reg = p.Reg
	r.To = p.To
	obj.Nopout(p)
}
Пример #2
0
func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
	// MOVW			g_stackguard(g), R1
	p = obj.Appendp(ctxt, p)

	p.As = AMOVW
	p.From.Type = obj.TYPE_MEM
	p.From.Reg = REGG
	p.From.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
	if ctxt.Cursym.Cfunc != 0 {
		p.From.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
	}
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R1

	if framesize <= obj.StackSmall {
		// small stack: SP < stackguard
		//	CMP	stackguard, SP
		p = obj.Appendp(ctxt, p)

		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.Reg = REGSP
	} else if framesize <= obj.StackBig {
		// large stack: SP-framesize < stackguard-StackSmall
		//	MOVW $-framesize(SP), R2
		//	CMP stackguard, R2
		p = obj.Appendp(ctxt, p)

		p.As = AMOVW
		p.From.Type = obj.TYPE_ADDR
		p.From.Reg = REGSP
		p.From.Offset = int64(-framesize)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.Reg = REG_R2
	} else {
		// Such a large stack we need to protect against wraparound
		// if SP is close to zero.
		//	SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
		// The +StackGuard on both sides is required to keep the left side positive:
		// SP is allowed to be slightly below stackguard. See stack.h.
		//	CMP $StackPreempt, R1
		//	MOVW.NE $StackGuard(SP), R2
		//	SUB.NE R1, R2
		//	MOVW.NE $(framesize+(StackGuard-StackSmall)), R3
		//	CMP.NE R3, R2
		p = obj.Appendp(ctxt, p)

		p.As = ACMP
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(uint32(obj.StackPreempt & (1<<32 - 1)))
		p.Reg = REG_R1

		p = obj.Appendp(ctxt, p)
		p.As = AMOVW
		p.From.Type = obj.TYPE_ADDR
		p.From.Reg = REGSP
		p.From.Offset = obj.StackGuard
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2
		p.Scond = C_SCOND_NE

		p = obj.Appendp(ctxt, p)
		p.As = ASUB
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2
		p.Scond = C_SCOND_NE

		p = obj.Appendp(ctxt, p)
		p.As = AMOVW
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R3
		p.Scond = C_SCOND_NE

		p = obj.Appendp(ctxt, p)
		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R3
		p.Reg = REG_R2
		p.Scond = C_SCOND_NE
	}

	// BLS call-to-morestack
	bls := obj.Appendp(ctxt, p)
	bls.As = ABLS
	bls.To.Type = obj.TYPE_BRANCH

	var last *obj.Prog
	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
	}

	spfix := obj.Appendp(ctxt, last)
	spfix.As = obj.ANOP
	spfix.Spadj = -framesize

	// MOVW	LR, R3
	movw := obj.Appendp(ctxt, spfix)
	movw.As = AMOVW
	movw.From.Type = obj.TYPE_REG
	movw.From.Reg = REGLINK
	movw.To.Type = obj.TYPE_REG
	movw.To.Reg = REG_R3

	bls.Pcond = movw

	// BL runtime.morestack
	call := obj.Appendp(ctxt, movw)
	call.As = obj.ACALL
	call.To.Type = obj.TYPE_BRANCH
	morestack := "runtime.morestack"
	switch {
	case ctxt.Cursym.Cfunc != 0:
		morestack = "runtime.morestackc"
	case ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0:
		morestack = "runtime.morestack_noctxt"
	}
	call.To.Sym = obj.Linklookup(ctxt, morestack, 0)

	// B start
	b := obj.Appendp(ctxt, call)
	b.As = obj.AJMP
	b.To.Type = obj.TYPE_BRANCH
	b.Pcond = ctxt.Cursym.Text.Link
	b.Spadj = +framesize

	return bls
}
Пример #3
0
func progedit(ctxt *obj.Link, p *obj.Prog) {
	p.From.Class = 0
	p.To.Class = 0

	// Rewrite B/BL to symbol as TYPE_BRANCH.
	switch p.As {
	case AB,
		ABL,
		obj.ADUFFZERO,
		obj.ADUFFCOPY:
		if p.To.Type == obj.TYPE_MEM && (p.To.Name == obj.NAME_EXTERN || p.To.Name == obj.NAME_STATIC) && p.To.Sym != nil {
			p.To.Type = obj.TYPE_BRANCH
		}
	}

	// Replace TLS register fetches on older ARM procesors.
	switch p.As {
	// Treat MRC 15, 0, <reg>, C13, C0, 3 specially.
	case AMRC:
		if p.To.Offset&0xffff0fff == 0xee1d0f70 {
			// Because the instruction might be rewriten to a BL which returns in R0
			// the register must be zero.
			if p.To.Offset&0xf000 != 0 {
				ctxt.Diag("%v: TLS MRC instruction must write to R0 as it might get translated into a BL instruction", p.Line())
			}

			if ctxt.Goarm < 7 {
				// Replace it with BL runtime.read_tls_fallback(SB) for ARM CPUs that lack the tls extension.
				if progedit_tlsfallback == nil {
					progedit_tlsfallback = obj.Linklookup(ctxt, "runtime.read_tls_fallback", 0)
				}

				// MOVW	LR, R11
				p.As = AMOVW

				p.From.Type = obj.TYPE_REG
				p.From.Reg = REGLINK
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REGTMP

				// BL	runtime.read_tls_fallback(SB)
				p = obj.Appendp(ctxt, p)

				p.As = ABL
				p.To.Type = obj.TYPE_BRANCH
				p.To.Sym = progedit_tlsfallback
				p.To.Offset = 0

				// MOVW	R11, LR
				p = obj.Appendp(ctxt, p)

				p.As = AMOVW
				p.From.Type = obj.TYPE_REG
				p.From.Reg = REGTMP
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REGLINK
				break
			}
		}

		// Otherwise, MRC/MCR instructions need no further treatment.
		p.As = AWORD
	}

	// Rewrite float constants to values stored in memory.
	switch p.As {
	case AMOVF:
		if p.From.Type == obj.TYPE_FCONST && chipfloat5(ctxt, p.From.Val.(float64)) < 0 && (chipzero5(ctxt, p.From.Val.(float64)) < 0 || p.Scond&C_SCOND != C_SCOND_NONE) {
			f32 := float32(p.From.Val.(float64))
			i32 := math.Float32bits(f32)
			literal := fmt.Sprintf("$f32.%08x", i32)
			s := obj.Linklookup(ctxt, literal, 0)
			p.From.Type = obj.TYPE_MEM
			p.From.Sym = s
			p.From.Name = obj.NAME_EXTERN
			p.From.Offset = 0
		}

	case AMOVD:
		if p.From.Type == obj.TYPE_FCONST && chipfloat5(ctxt, p.From.Val.(float64)) < 0 && (chipzero5(ctxt, p.From.Val.(float64)) < 0 || p.Scond&C_SCOND != C_SCOND_NONE) {
			i64 := math.Float64bits(p.From.Val.(float64))
			literal := fmt.Sprintf("$f64.%016x", i64)
			s := obj.Linklookup(ctxt, literal, 0)
			p.From.Type = obj.TYPE_MEM
			p.From.Sym = s
			p.From.Name = obj.NAME_EXTERN
			p.From.Offset = 0
		}
	}

	if ctxt.Flag_dynlink {
		rewriteToUseGot(ctxt, p)
	}
}
Пример #4
0
func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
	autosize := int32(0)

	ctxt.Cursym = cursym

	if cursym.Text == nil || cursym.Text.Link == nil {
		return
	}

	softfloat(ctxt, cursym)

	p := cursym.Text
	autoffset := int32(p.To.Offset)
	if autoffset < 0 {
		autoffset = 0
	}
	cursym.Locals = autoffset
	cursym.Args = p.To.Val.(int32)

	/*
	 * find leaf subroutines
	 * strip NOPs
	 * expand RET
	 * expand BECOME pseudo
	 */
	var q1 *obj.Prog
	var q *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		switch p.As {
		case obj.ATEXT:
			p.Mark |= LEAF

		case obj.ARET:
			break

		case ADIV, ADIVU, AMOD, AMODU:
			q = p
			if ctxt.Sym_div == nil {
				initdiv(ctxt)
			}
			cursym.Text.Mark &^= LEAF
			continue

		case obj.ANOP:
			q1 = p.Link
			q.Link = q1 /* q is non-nop */
			if q1 != nil {
				q1.Mark |= p.Mark
			}
			continue

		case ABL,
			ABX,
			obj.ADUFFZERO,
			obj.ADUFFCOPY:
			cursym.Text.Mark &^= LEAF
			fallthrough

		case AB,
			ABEQ,
			ABNE,
			ABCS,
			ABHS,
			ABCC,
			ABLO,
			ABMI,
			ABPL,
			ABVS,
			ABVC,
			ABHI,
			ABLS,
			ABGE,
			ABLT,
			ABGT,
			ABLE:
			q1 = p.Pcond
			if q1 != nil {
				for q1.As == obj.ANOP {
					q1 = q1.Link
					p.Pcond = q1
				}
			}
		}

		q = p
	}

	var o int
	var p1 *obj.Prog
	var p2 *obj.Prog
	var q2 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		o = int(p.As)
		switch o {
		case obj.ATEXT:
			autosize = int32(p.To.Offset + 4)
			if autosize <= 4 {
				if cursym.Text.Mark&LEAF != 0 {
					p.To.Offset = -4
					autosize = 0
				}
			}

			if autosize == 0 && cursym.Text.Mark&LEAF == 0 {
				if ctxt.Debugvlog != 0 {
					fmt.Fprintf(ctxt.Bso, "save suppressed in: %s\n", cursym.Name)
					ctxt.Bso.Flush()
				}

				cursym.Text.Mark |= LEAF
			}

			if cursym.Text.Mark&LEAF != 0 {
				cursym.Leaf = 1
				if autosize == 0 {
					break
				}
			}

			if p.From3.Offset&obj.NOSPLIT == 0 {
				p = stacksplit(ctxt, p, autosize) // emit split check
			}

			// MOVW.W		R14,$-autosize(SP)
			p = obj.Appendp(ctxt, p)

			p.As = AMOVW
			p.Scond |= C_WBIT
			p.From.Type = obj.TYPE_REG
			p.From.Reg = REGLINK
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = int64(-autosize)
			p.To.Reg = REGSP
			p.Spadj = autosize

			if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
				//
				//	MOVW g_panic(g), R1
				//	CMP $0, R1
				//	B.EQ end
				//	MOVW panic_argp(R1), R2
				//	ADD $(autosize+4), R13, R3
				//	CMP R2, R3
				//	B.NE end
				//	ADD $4, R13, R4
				//	MOVW R4, panic_argp(R1)
				// end:
				//	NOP
				//
				// The NOP is needed to give the jumps somewhere to land.
				// It is a liblink NOP, not an ARM NOP: it encodes to 0 instruction bytes.

				p = obj.Appendp(ctxt, p)

				p.As = AMOVW
				p.From.Type = obj.TYPE_MEM
				p.From.Reg = REGG
				p.From.Offset = 4 * int64(ctxt.Arch.Ptrsize) // G.panic
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REG_R1

				p = obj.Appendp(ctxt, p)
				p.As = ACMP
				p.From.Type = obj.TYPE_CONST
				p.From.Offset = 0
				p.Reg = REG_R1

				p = obj.Appendp(ctxt, p)
				p.As = ABEQ
				p.To.Type = obj.TYPE_BRANCH
				p1 = p

				p = obj.Appendp(ctxt, p)
				p.As = AMOVW
				p.From.Type = obj.TYPE_MEM
				p.From.Reg = REG_R1
				p.From.Offset = 0 // Panic.argp
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REG_R2

				p = obj.Appendp(ctxt, p)
				p.As = AADD
				p.From.Type = obj.TYPE_CONST
				p.From.Offset = int64(autosize) + 4
				p.Reg = REG_R13
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REG_R3

				p = obj.Appendp(ctxt, p)
				p.As = ACMP
				p.From.Type = obj.TYPE_REG
				p.From.Reg = REG_R2
				p.Reg = REG_R3

				p = obj.Appendp(ctxt, p)
				p.As = ABNE
				p.To.Type = obj.TYPE_BRANCH
				p2 = p

				p = obj.Appendp(ctxt, p)
				p.As = AADD
				p.From.Type = obj.TYPE_CONST
				p.From.Offset = 4
				p.Reg = REG_R13
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REG_R4

				p = obj.Appendp(ctxt, p)
				p.As = AMOVW
				p.From.Type = obj.TYPE_REG
				p.From.Reg = REG_R4
				p.To.Type = obj.TYPE_MEM
				p.To.Reg = REG_R1
				p.To.Offset = 0 // Panic.argp

				p = obj.Appendp(ctxt, p)

				p.As = obj.ANOP
				p1.Pcond = p
				p2.Pcond = p
			}

		case obj.ARET:
			obj.Nocache(p)
			if cursym.Text.Mark&LEAF != 0 {
				if autosize == 0 {
					p.As = AB
					p.From = obj.Addr{}
					if p.To.Sym != nil { // retjmp
						p.To.Type = obj.TYPE_BRANCH
					} else {
						p.To.Type = obj.TYPE_MEM
						p.To.Offset = 0
						p.To.Reg = REGLINK
					}

					break
				}
			}

			p.As = AMOVW
			p.Scond |= C_PBIT
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = int64(autosize)
			p.From.Reg = REGSP
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REGPC

			// If there are instructions following
			// this ARET, they come from a branch
			// with the same stackframe, so no spadj.
			if p.To.Sym != nil { // retjmp
				p.To.Reg = REGLINK
				q2 = obj.Appendp(ctxt, p)
				q2.As = AB
				q2.To.Type = obj.TYPE_BRANCH
				q2.To.Sym = p.To.Sym
				p.To.Sym = nil
				p = q2
			}

		case AADD:
			if p.From.Type == obj.TYPE_CONST && p.From.Reg == 0 && p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP {
				p.Spadj = int32(-p.From.Offset)
			}

		case ASUB:
			if p.From.Type == obj.TYPE_CONST && p.From.Reg == 0 && p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP {
				p.Spadj = int32(p.From.Offset)
			}

		case ADIV, ADIVU, AMOD, AMODU:
			if cursym.Text.From3.Offset&obj.NOSPLIT != 0 {
				ctxt.Diag("cannot divide in NOSPLIT function")
			}
			if ctxt.Debugdivmod != 0 {
				break
			}
			if p.From.Type != obj.TYPE_REG {
				break
			}
			if p.To.Type != obj.TYPE_REG {
				break
			}

			// Make copy because we overwrite p below.
			q1 := *p
			if q1.Reg == REGTMP || q1.Reg == 0 && q1.To.Reg == REGTMP {
				ctxt.Diag("div already using REGTMP: %v", p)
			}

			/* MOV m(g),REGTMP */
			p.As = AMOVW
			p.Lineno = q1.Lineno
			p.From.Type = obj.TYPE_MEM
			p.From.Reg = REGG
			p.From.Offset = 6 * 4 // offset of g.m
			p.Reg = 0
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REGTMP

			/* MOV a,m_divmod(REGTMP) */
			p = obj.Appendp(ctxt, p)
			p.As = AMOVW
			p.Lineno = q1.Lineno
			p.From.Type = obj.TYPE_REG
			p.From.Reg = q1.From.Reg
			p.To.Type = obj.TYPE_MEM
			p.To.Reg = REGTMP
			p.To.Offset = 8 * 4 // offset of m.divmod

			/* MOV b,REGTMP */
			p = obj.Appendp(ctxt, p)
			p.As = AMOVW
			p.Lineno = q1.Lineno
			p.From.Type = obj.TYPE_REG
			p.From.Reg = q1.Reg
			if q1.Reg == 0 {
				p.From.Reg = q1.To.Reg
			}
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REGTMP
			p.To.Offset = 0

			/* CALL appropriate */
			p = obj.Appendp(ctxt, p)
			p.As = ABL
			p.Lineno = q1.Lineno
			p.To.Type = obj.TYPE_BRANCH
			switch o {
			case ADIV:
				p.To.Sym = ctxt.Sym_div

			case ADIVU:
				p.To.Sym = ctxt.Sym_divu

			case AMOD:
				p.To.Sym = ctxt.Sym_mod

			case AMODU:
				p.To.Sym = ctxt.Sym_modu
			}

			/* MOV REGTMP, b */
			p = obj.Appendp(ctxt, p)
			p.As = AMOVW
			p.Lineno = q1.Lineno
			p.From.Type = obj.TYPE_REG
			p.From.Reg = REGTMP
			p.From.Offset = 0
			p.To.Type = obj.TYPE_REG
			p.To.Reg = q1.To.Reg

		case AMOVW:
			if (p.Scond&C_WBIT != 0) && p.To.Type == obj.TYPE_MEM && p.To.Reg == REGSP {
				p.Spadj = int32(-p.To.Offset)
			}
			if (p.Scond&C_PBIT != 0) && p.From.Type == obj.TYPE_MEM && p.From.Reg == REGSP && p.To.Reg != REGPC {
				p.Spadj = int32(-p.From.Offset)
			}
			if p.From.Type == obj.TYPE_ADDR && p.From.Reg == REGSP && p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP {
				p.Spadj = int32(-p.From.Offset)
			}
		}
	}
}
Пример #5
0
// Rewrite p, if necessary, to access global data via the global offset table.
func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
	if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
		//     ADUFFxxx $offset
		// becomes
		//     MOVW runtime.duffxxx@GOT, R9
		//     ADD $offset, R9
		//     CALL (R9)
		var sym *obj.LSym
		if p.As == obj.ADUFFZERO {
			sym = obj.Linklookup(ctxt, "runtime.duffzero", 0)
		} else {
			sym = obj.Linklookup(ctxt, "runtime.duffcopy", 0)
		}
		offset := p.To.Offset
		p.As = AMOVW
		p.From.Type = obj.TYPE_MEM
		p.From.Name = obj.NAME_GOTREF
		p.From.Sym = sym
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R9
		p.To.Name = obj.NAME_NONE
		p.To.Offset = 0
		p.To.Sym = nil
		p1 := obj.Appendp(ctxt, p)
		p1.As = AADD
		p1.From.Type = obj.TYPE_CONST
		p1.From.Offset = offset
		p1.To.Type = obj.TYPE_REG
		p1.To.Reg = REG_R9
		p2 := obj.Appendp(ctxt, p1)
		p2.As = obj.ACALL
		p2.To.Type = obj.TYPE_MEM
		p2.To.Reg = REG_R9
		return
	}

	// We only care about global data: NAME_EXTERN means a global
	// symbol in the Go sense, and p.Sym.Local is true for a few
	// internally defined symbols.
	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
		// MOVW $sym, Rx becomes MOVW sym@GOT, Rx
		// MOVW $sym+<off>, Rx becomes MOVW sym@GOT, Rx; ADD <off>, Rx
		if p.As != AMOVW {
			ctxt.Diag("do not know how to handle TYPE_ADDR in %v with -dynlink", p)
		}
		if p.To.Type != obj.TYPE_REG {
			ctxt.Diag("do not know how to handle LEAQ-type insn to non-register in %v with -dynlink", p)
		}
		p.From.Type = obj.TYPE_MEM
		p.From.Name = obj.NAME_GOTREF
		if p.From.Offset != 0 {
			q := obj.Appendp(ctxt, p)
			q.As = AADD
			q.From.Type = obj.TYPE_CONST
			q.From.Offset = p.From.Offset
			q.To = p.To
			p.From.Offset = 0
		}
	}
	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
		ctxt.Diag("don't know how to handle %v with -dynlink", p)
	}
	var source *obj.Addr
	// MOVx sym, Ry becomes MOVW sym@GOT, R9; MOVx (R9), Ry
	// MOVx Ry, sym becomes MOVW sym@GOT, R9; MOVx Ry, (R9)
	// An addition may be inserted between the two MOVs if there is an offset.
	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
		if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
			ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
		}
		source = &p.From
	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
		source = &p.To
	} else {
		return
	}
	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ACALL || p.As == obj.ARET || p.As == obj.AJMP {
		return
	}
	if source.Sym.Type == obj.STLSBSS {
		return
	}
	if source.Type != obj.TYPE_MEM {
		ctxt.Diag("don't know how to handle %v with -dynlink", p)
	}
	p1 := obj.Appendp(ctxt, p)
	p2 := obj.Appendp(ctxt, p1)

	p1.As = AMOVW
	p1.From.Type = obj.TYPE_MEM
	p1.From.Sym = source.Sym
	p1.From.Name = obj.NAME_GOTREF
	p1.To.Type = obj.TYPE_REG
	p1.To.Reg = REG_R9

	p2.As = p.As
	p2.From = p.From
	p2.To = p.To
	if p.From.Name == obj.NAME_EXTERN {
		p2.From.Reg = REG_R9
		p2.From.Name = obj.NAME_NONE
		p2.From.Sym = nil
	} else if p.To.Name == obj.NAME_EXTERN {
		p2.To.Reg = REG_R9
		p2.To.Name = obj.NAME_NONE
		p2.To.Sym = nil
	} else {
		return
	}
	obj.Nopout(p)
}
Пример #6
0
func progedit(ctxt *obj.Link, p *obj.Prog) {
	// Maintain information about code generation mode.
	if ctxt.Mode == 0 {
		ctxt.Mode = ctxt.Arch.Regsize * 8
	}
	p.Mode = int8(ctxt.Mode)

	switch p.As {
	case AMODE:
		if p.From.Type == obj.TYPE_CONST || (p.From.Type == obj.TYPE_MEM && p.From.Reg == REG_NONE) {
			switch int(p.From.Offset) {
			case 16, 32, 64:
				ctxt.Mode = int(p.From.Offset)
			}
		}
		obj.Nopout(p)
	}

	// Thread-local storage references use the TLS pseudo-register.
	// As a register, TLS refers to the thread-local storage base, and it
	// can only be loaded into another register:
	//
	//         MOVQ TLS, AX
	//
	// An offset from the thread-local storage base is written off(reg)(TLS*1).
	// Semantically it is off(reg), but the (TLS*1) annotation marks this as
	// indexing from the loaded TLS base. This emits a relocation so that
	// if the linker needs to adjust the offset, it can. For example:
	//
	//         MOVQ TLS, AX
	//         MOVQ 0(AX)(TLS*1), CX // load g into CX
	//
	// On systems that support direct access to the TLS memory, this
	// pair of instructions can be reduced to a direct TLS memory reference:
	//
	//         MOVQ 0(TLS), CX // load g into CX
	//
	// The 2-instruction and 1-instruction forms correspond to the two code
	// sequences for loading a TLS variable in the local exec model given in "ELF
	// Handling For Thread-Local Storage".
	//
	// We apply this rewrite on systems that support the 1-instruction form.
	// The decision is made using only the operating system and the -shared flag,
	// not the link mode. If some link modes on a particular operating system
	// require the 2-instruction form, then all builds for that operating system
	// will use the 2-instruction form, so that the link mode decision can be
	// delayed to link time.
	//
	// In this way, all supported systems use identical instructions to
	// access TLS, and they are rewritten appropriately first here in
	// liblink and then finally using relocations in the linker.
	//
	// When -shared is passed, we leave the code in the 2-instruction form but
	// assemble (and relocate) them in different ways to generate the initial
	// exec code sequence. It's a bit of a fluke that this is possible without
	// rewriting the instructions more comprehensively, and it only does because
	// we only support a single TLS variable (g).

	if canuse1insntls(ctxt) {
		// Reduce 2-instruction sequence to 1-instruction sequence.
		// Sequences like
		//	MOVQ TLS, BX
		//	... off(BX)(TLS*1) ...
		// become
		//	NOP
		//	... off(TLS) ...
		//
		// TODO(rsc): Remove the Hsolaris special case. It exists only to
		// guarantee we are producing byte-identical binaries as before this code.
		// But it should be unnecessary.
		if (p.As == AMOVQ || p.As == AMOVL) && p.From.Type == obj.TYPE_REG && p.From.Reg == REG_TLS && p.To.Type == obj.TYPE_REG && REG_AX <= p.To.Reg && p.To.Reg <= REG_R15 && ctxt.Headtype != obj.Hsolaris {
			obj.Nopout(p)
		}
		if p.From.Type == obj.TYPE_MEM && p.From.Index == REG_TLS && REG_AX <= p.From.Reg && p.From.Reg <= REG_R15 {
			p.From.Reg = REG_TLS
			p.From.Scale = 0
			p.From.Index = REG_NONE
		}

		if p.To.Type == obj.TYPE_MEM && p.To.Index == REG_TLS && REG_AX <= p.To.Reg && p.To.Reg <= REG_R15 {
			p.To.Reg = REG_TLS
			p.To.Scale = 0
			p.To.Index = REG_NONE
		}
	} else {
		// load_g_cx, below, always inserts the 1-instruction sequence. Rewrite it
		// as the 2-instruction sequence if necessary.
		//	MOVQ 0(TLS), BX
		// becomes
		//	MOVQ TLS, BX
		//	MOVQ 0(BX)(TLS*1), BX
		if (p.As == AMOVQ || p.As == AMOVL) && p.From.Type == obj.TYPE_MEM && p.From.Reg == REG_TLS && p.To.Type == obj.TYPE_REG && REG_AX <= p.To.Reg && p.To.Reg <= REG_R15 {
			q := obj.Appendp(ctxt, p)
			q.As = p.As
			q.From = p.From
			q.From.Type = obj.TYPE_MEM
			q.From.Reg = p.To.Reg
			q.From.Index = REG_TLS
			q.From.Scale = 2 // TODO: use 1
			q.To = p.To
			p.From.Type = obj.TYPE_REG
			p.From.Reg = REG_TLS
			p.From.Index = REG_NONE
			p.From.Offset = 0
		}
	}

	// TODO: Remove.
	if ctxt.Headtype == obj.Hwindows && p.Mode == 64 || ctxt.Headtype == obj.Hplan9 {
		if p.From.Scale == 1 && p.From.Index == REG_TLS {
			p.From.Scale = 2
		}
		if p.To.Scale == 1 && p.To.Index == REG_TLS {
			p.To.Scale = 2
		}
	}

	// Rewrite 0 to $0 in 3rd argment to CMPPS etc.
	// That's what the tables expect.
	switch p.As {
	case ACMPPD, ACMPPS, ACMPSD, ACMPSS:
		if p.To.Type == obj.TYPE_MEM && p.To.Name == obj.NAME_NONE && p.To.Reg == REG_NONE && p.To.Index == REG_NONE && p.To.Sym == nil {
			p.To.Type = obj.TYPE_CONST
		}
	}

	// Rewrite CALL/JMP/RET to symbol as TYPE_BRANCH.
	switch p.As {
	case obj.ACALL, obj.AJMP, obj.ARET:
		if p.To.Type == obj.TYPE_MEM && (p.To.Name == obj.NAME_EXTERN || p.To.Name == obj.NAME_STATIC) && p.To.Sym != nil {
			p.To.Type = obj.TYPE_BRANCH
		}
	}

	// Rewrite MOVL/MOVQ $XXX(FP/SP) as LEAL/LEAQ.
	if p.From.Type == obj.TYPE_ADDR && (ctxt.Arch.Thechar == '6' || p.From.Name != obj.NAME_EXTERN && p.From.Name != obj.NAME_STATIC) {
		switch p.As {
		case AMOVL:
			p.As = ALEAL
			p.From.Type = obj.TYPE_MEM
		case AMOVQ:
			p.As = ALEAQ
			p.From.Type = obj.TYPE_MEM
		}
	}

	if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
		if p.From3 != nil {
			nacladdr(ctxt, p, p.From3)
		}
		nacladdr(ctxt, p, &p.From)
		nacladdr(ctxt, p, &p.To)
	}

	// Rewrite float constants to values stored in memory.
	switch p.As {
	// Convert AMOVSS $(0), Xx to AXORPS Xx, Xx
	case AMOVSS:
		if p.From.Type == obj.TYPE_FCONST {
			if p.From.Val.(float64) == 0 {
				if p.To.Type == obj.TYPE_REG && REG_X0 <= p.To.Reg && p.To.Reg <= REG_X15 {
					p.As = AXORPS
					p.From = p.To
					break
				}
			}
		}
		fallthrough

	case AFMOVF,
		AFADDF,
		AFSUBF,
		AFSUBRF,
		AFMULF,
		AFDIVF,
		AFDIVRF,
		AFCOMF,
		AFCOMFP,
		AADDSS,
		ASUBSS,
		AMULSS,
		ADIVSS,
		ACOMISS,
		AUCOMISS:
		if p.From.Type == obj.TYPE_FCONST {
			f32 := float32(p.From.Val.(float64))
			i32 := math.Float32bits(f32)
			literal := fmt.Sprintf("$f32.%08x", i32)
			s := obj.Linklookup(ctxt, literal, 0)
			p.From.Type = obj.TYPE_MEM
			p.From.Name = obj.NAME_EXTERN
			p.From.Sym = s
			p.From.Sym.Local = true
			p.From.Offset = 0
		}

	case AMOVSD:
		// Convert AMOVSD $(0), Xx to AXORPS Xx, Xx
		if p.From.Type == obj.TYPE_FCONST {
			if p.From.Val.(float64) == 0 {
				if p.To.Type == obj.TYPE_REG && REG_X0 <= p.To.Reg && p.To.Reg <= REG_X15 {
					p.As = AXORPS
					p.From = p.To
					break
				}
			}
		}
		fallthrough

	case AFMOVD,
		AFADDD,
		AFSUBD,
		AFSUBRD,
		AFMULD,
		AFDIVD,
		AFDIVRD,
		AFCOMD,
		AFCOMDP,
		AADDSD,
		ASUBSD,
		AMULSD,
		ADIVSD,
		ACOMISD,
		AUCOMISD:
		if p.From.Type == obj.TYPE_FCONST {
			i64 := math.Float64bits(p.From.Val.(float64))
			literal := fmt.Sprintf("$f64.%016x", i64)
			s := obj.Linklookup(ctxt, literal, 0)
			p.From.Type = obj.TYPE_MEM
			p.From.Name = obj.NAME_EXTERN
			p.From.Sym = s
			p.From.Sym.Local = true
			p.From.Offset = 0
		}
	}

	if ctxt.Flag_dynlink {
		rewriteToUseGot(ctxt, p)
	}

	if ctxt.Flag_shared != 0 && p.Mode == 32 {
		rewriteToPcrel(ctxt, p)
	}
}
Пример #7
0
func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
	if ctxt.Headtype == obj.Hplan9 && ctxt.Plan9privates == nil {
		ctxt.Plan9privates = obj.Linklookup(ctxt, "_privates", 0)
	}

	ctxt.Cursym = cursym

	if cursym.Text == nil || cursym.Text.Link == nil {
		return
	}

	p := cursym.Text
	autoffset := int32(p.To.Offset)
	if autoffset < 0 {
		autoffset = 0
	}

	var bpsize int
	if p.Mode == 64 && obj.Framepointer_enabled != 0 && autoffset > 0 {
		// Make room for to save a base pointer.  If autoffset == 0,
		// this might do something special like a tail jump to
		// another function, so in that case we omit this.
		bpsize = ctxt.Arch.Ptrsize

		autoffset += int32(bpsize)
		p.To.Offset += int64(bpsize)
	} else {
		bpsize = 0
	}

	textarg := int64(p.To.Val.(int32))
	cursym.Args = int32(textarg)
	cursym.Locals = int32(p.To.Offset)

	// TODO(rsc): Remove.
	if p.Mode == 32 && cursym.Locals < 0 {
		cursym.Locals = 0
	}

	// TODO(rsc): Remove 'p.Mode == 64 &&'.
	if p.Mode == 64 && autoffset < obj.StackSmall && p.From3Offset()&obj.NOSPLIT == 0 {
		for q := p; q != nil; q = q.Link {
			if q.As == obj.ACALL {
				goto noleaf
			}
			if (q.As == obj.ADUFFCOPY || q.As == obj.ADUFFZERO) && autoffset >= obj.StackSmall-8 {
				goto noleaf
			}
		}

		p.From3.Offset |= obj.NOSPLIT
	noleaf:
	}

	if p.From3Offset()&obj.NOSPLIT == 0 || p.From3Offset()&obj.WRAPPER != 0 {
		p = obj.Appendp(ctxt, p)
		p = load_g_cx(ctxt, p) // load g into CX
	}

	if cursym.Text.From3Offset()&obj.NOSPLIT == 0 {
		p = stacksplit(ctxt, p, autoffset, int32(textarg)) // emit split check
	}

	if autoffset != 0 {
		if autoffset%int32(ctxt.Arch.Regsize) != 0 {
			ctxt.Diag("unaligned stack size %d", autoffset)
		}
		p = obj.Appendp(ctxt, p)
		p.As = AADJSP
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(autoffset)
		p.Spadj = autoffset
	} else {
		// zero-byte stack adjustment.
		// Insert a fake non-zero adjustment so that stkcheck can
		// recognize the end of the stack-splitting prolog.
		p = obj.Appendp(ctxt, p)

		p.As = obj.ANOP
		p.Spadj = int32(-ctxt.Arch.Ptrsize)
		p = obj.Appendp(ctxt, p)
		p.As = obj.ANOP
		p.Spadj = int32(ctxt.Arch.Ptrsize)
	}

	deltasp := autoffset

	if bpsize > 0 {
		// Save caller's BP
		p = obj.Appendp(ctxt, p)

		p.As = AMOVQ
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_BP
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = REG_SP
		p.To.Scale = 1
		p.To.Offset = int64(autoffset) - int64(bpsize)

		// Move current frame to BP
		p = obj.Appendp(ctxt, p)

		p.As = ALEAQ
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = REG_SP
		p.From.Scale = 1
		p.From.Offset = int64(autoffset) - int64(bpsize)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_BP
	}

	if cursym.Text.From3Offset()&obj.WRAPPER != 0 {
		// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
		//
		//	MOVQ g_panic(CX), BX
		//	TESTQ BX, BX
		//	JEQ end
		//	LEAQ (autoffset+8)(SP), DI
		//	CMPQ panic_argp(BX), DI
		//	JNE end
		//	MOVQ SP, panic_argp(BX)
		// end:
		//	NOP
		//
		// The NOP is needed to give the jumps somewhere to land.
		// It is a liblink NOP, not an x86 NOP: it encodes to 0 instruction bytes.

		p = obj.Appendp(ctxt, p)

		p.As = AMOVQ
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = REG_CX
		p.From.Offset = 4 * int64(ctxt.Arch.Ptrsize) // G.panic
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_BX
		if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
			p.As = AMOVL
			p.From.Type = obj.TYPE_MEM
			p.From.Reg = REG_R15
			p.From.Scale = 1
			p.From.Index = REG_CX
		}
		if p.Mode == 32 {
			p.As = AMOVL
		}

		p = obj.Appendp(ctxt, p)
		p.As = ATESTQ
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_BX
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_BX
		if ctxt.Headtype == obj.Hnacl || p.Mode == 32 {
			p.As = ATESTL
		}

		p = obj.Appendp(ctxt, p)
		p.As = AJEQ
		p.To.Type = obj.TYPE_BRANCH
		p1 := p

		p = obj.Appendp(ctxt, p)
		p.As = ALEAQ
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = REG_SP
		p.From.Offset = int64(autoffset) + int64(ctxt.Arch.Regsize)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_DI
		if ctxt.Headtype == obj.Hnacl || p.Mode == 32 {
			p.As = ALEAL
		}

		p = obj.Appendp(ctxt, p)
		p.As = ACMPQ
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = REG_BX
		p.From.Offset = 0 // Panic.argp
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_DI
		if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
			p.As = ACMPL
			p.From.Type = obj.TYPE_MEM
			p.From.Reg = REG_R15
			p.From.Scale = 1
			p.From.Index = REG_BX
		}
		if p.Mode == 32 {
			p.As = ACMPL
		}

		p = obj.Appendp(ctxt, p)
		p.As = AJNE
		p.To.Type = obj.TYPE_BRANCH
		p2 := p

		p = obj.Appendp(ctxt, p)
		p.As = AMOVQ
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_SP
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = REG_BX
		p.To.Offset = 0 // Panic.argp
		if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
			p.As = AMOVL
			p.To.Type = obj.TYPE_MEM
			p.To.Reg = REG_R15
			p.To.Scale = 1
			p.To.Index = REG_BX
		}
		if p.Mode == 32 {
			p.As = AMOVL
		}

		p = obj.Appendp(ctxt, p)
		p.As = obj.ANOP
		p1.Pcond = p
		p2.Pcond = p
	}

	var a int
	var pcsize int
	for ; p != nil; p = p.Link {
		pcsize = int(p.Mode) / 8
		a = int(p.From.Name)
		if a == obj.NAME_AUTO {
			p.From.Offset += int64(deltasp) - int64(bpsize)
		}
		if a == obj.NAME_PARAM {
			p.From.Offset += int64(deltasp) + int64(pcsize)
		}
		if p.From3 != nil {
			a = int(p.From3.Name)
			if a == obj.NAME_AUTO {
				p.From3.Offset += int64(deltasp) - int64(bpsize)
			}
			if a == obj.NAME_PARAM {
				p.From3.Offset += int64(deltasp) + int64(pcsize)
			}
		}
		a = int(p.To.Name)
		if a == obj.NAME_AUTO {
			p.To.Offset += int64(deltasp) - int64(bpsize)
		}
		if a == obj.NAME_PARAM {
			p.To.Offset += int64(deltasp) + int64(pcsize)
		}

		switch p.As {
		default:
			continue

		case APUSHL, APUSHFL:
			deltasp += 4
			p.Spadj = 4
			continue

		case APUSHQ, APUSHFQ:
			deltasp += 8
			p.Spadj = 8
			continue

		case APUSHW, APUSHFW:
			deltasp += 2
			p.Spadj = 2
			continue

		case APOPL, APOPFL:
			deltasp -= 4
			p.Spadj = -4
			continue

		case APOPQ, APOPFQ:
			deltasp -= 8
			p.Spadj = -8
			continue

		case APOPW, APOPFW:
			deltasp -= 2
			p.Spadj = -2
			continue

		case obj.ARET:
			break
		}

		if autoffset != deltasp {
			ctxt.Diag("unbalanced PUSH/POP")
		}

		if autoffset != 0 {
			if bpsize > 0 {
				// Restore caller's BP
				p.As = AMOVQ

				p.From.Type = obj.TYPE_MEM
				p.From.Reg = REG_SP
				p.From.Scale = 1
				p.From.Offset = int64(autoffset) - int64(bpsize)
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REG_BP
				p = obj.Appendp(ctxt, p)
			}

			p.As = AADJSP
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = int64(-autoffset)
			p.Spadj = -autoffset
			p = obj.Appendp(ctxt, p)
			p.As = obj.ARET

			// If there are instructions following
			// this ARET, they come from a branch
			// with the same stackframe, so undo
			// the cleanup.
			p.Spadj = +autoffset
		}

		if p.To.Sym != nil { // retjmp
			p.As = obj.AJMP
		}
	}
}

func indir_cx(ctxt *obj.Link, p *obj.Prog, a *obj.Addr) {
	if ctxt.Headtype == obj.Hnacl && p.Mode == 64 {
		a.Type = obj.TYPE_MEM
		a.Reg = REG_R15
		a.Index = REG_CX
		a.Scale = 1
		return
	}

	a.Type = obj.TYPE_MEM
	a.Reg = REG_CX
}

// Append code to p to load g into cx.
// Overwrites p with the first instruction (no first appendp).
// Overwriting p is unusual but it lets use this in both the
// prologue (caller must call appendp first) and in the epilogue.
// Returns last new instruction.
func load_g_cx(ctxt *obj.Link, p *obj.Prog) *obj.Prog {
	p.As = AMOVQ
	if ctxt.Arch.Ptrsize == 4 {
		p.As = AMOVL
	}
	p.From.Type = obj.TYPE_MEM
	p.From.Reg = REG_TLS
	p.From.Offset = 0
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_CX

	next := p.Link
	progedit(ctxt, p)
	for p.Link != next {
		p = p.Link
	}

	if p.From.Index == REG_TLS {
		p.From.Scale = 2
	}

	return p
}

// Append code to p to check for stack split.
// Appends to (does not overwrite) p.
// Assumes g is in CX.
// Returns last new instruction.
func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32, textarg int32) *obj.Prog {
	cmp := ACMPQ
	lea := ALEAQ
	mov := AMOVQ
	sub := ASUBQ

	if ctxt.Headtype == obj.Hnacl || p.Mode == 32 {
		cmp = ACMPL
		lea = ALEAL
		mov = AMOVL
		sub = ASUBL
	}

	var q1 *obj.Prog
	if framesize <= obj.StackSmall {
		// small stack: SP <= stackguard
		//	CMPQ SP, stackguard
		p = obj.Appendp(ctxt, p)

		p.As = int16(cmp)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_SP
		indir_cx(ctxt, p, &p.To)
		p.To.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
		if ctxt.Cursym.Cfunc != 0 {
			p.To.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
		}
	} else if framesize <= obj.StackBig {
		// large stack: SP-framesize <= stackguard-StackSmall
		//	LEAQ -xxx(SP), AX
		//	CMPQ AX, stackguard
		p = obj.Appendp(ctxt, p)

		p.As = int16(lea)
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = REG_SP
		p.From.Offset = -(int64(framesize) - obj.StackSmall)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_AX

		p = obj.Appendp(ctxt, p)
		p.As = int16(cmp)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_AX
		indir_cx(ctxt, p, &p.To)
		p.To.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
		if ctxt.Cursym.Cfunc != 0 {
			p.To.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
		}
	} else {
		// Such a large stack we need to protect against wraparound.
		// If SP is close to zero:
		//	SP-stackguard+StackGuard <= framesize + (StackGuard-StackSmall)
		// The +StackGuard on both sides is required to keep the left side positive:
		// SP is allowed to be slightly below stackguard. See stack.h.
		//
		// Preemption sets stackguard to StackPreempt, a very large value.
		// That breaks the math above, so we have to check for that explicitly.
		//	MOVQ	stackguard, CX
		//	CMPQ	CX, $StackPreempt
		//	JEQ	label-of-call-to-morestack
		//	LEAQ	StackGuard(SP), AX
		//	SUBQ	CX, AX
		//	CMPQ	AX, $(framesize+(StackGuard-StackSmall))

		p = obj.Appendp(ctxt, p)

		p.As = int16(mov)
		indir_cx(ctxt, p, &p.From)
		p.From.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
		if ctxt.Cursym.Cfunc != 0 {
			p.From.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
		}
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_SI

		p = obj.Appendp(ctxt, p)
		p.As = int16(cmp)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_SI
		p.To.Type = obj.TYPE_CONST
		p.To.Offset = obj.StackPreempt
		if p.Mode == 32 {
			p.To.Offset = int64(uint32(obj.StackPreempt & (1<<32 - 1)))
		}

		p = obj.Appendp(ctxt, p)
		p.As = AJEQ
		p.To.Type = obj.TYPE_BRANCH
		q1 = p

		p = obj.Appendp(ctxt, p)
		p.As = int16(lea)
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = REG_SP
		p.From.Offset = obj.StackGuard
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_AX

		p = obj.Appendp(ctxt, p)
		p.As = int16(sub)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_SI
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_AX

		p = obj.Appendp(ctxt, p)
		p.As = int16(cmp)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_AX
		p.To.Type = obj.TYPE_CONST
		p.To.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
	}

	// common
	jls := obj.Appendp(ctxt, p)
	jls.As = AJLS
	jls.To.Type = obj.TYPE_BRANCH

	var last *obj.Prog
	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
	}

	spfix := obj.Appendp(ctxt, last)
	spfix.As = obj.ANOP
	spfix.Spadj = -framesize

	call := obj.Appendp(ctxt, spfix)
	call.Lineno = ctxt.Cursym.Text.Lineno
	call.Mode = ctxt.Cursym.Text.Mode
	call.As = obj.ACALL
	call.To.Type = obj.TYPE_BRANCH
	morestack := "runtime.morestack"
	switch {
	case ctxt.Cursym.Cfunc != 0:
		morestack = "runtime.morestackc"
	case ctxt.Cursym.Text.From3Offset()&obj.NEEDCTXT == 0:
		morestack = "runtime.morestack_noctxt"
	}
	call.To.Sym = obj.Linklookup(ctxt, morestack, 0)

	jmp := obj.Appendp(ctxt, call)
	jmp.As = obj.AJMP
	jmp.To.Type = obj.TYPE_BRANCH
	jmp.Pcond = ctxt.Cursym.Text.Link
	jmp.Spadj = +framesize

	jls.Pcond = call
	if q1 != nil {
		q1.Pcond = call
	}

	return jls
}

func follow(ctxt *obj.Link, s *obj.LSym) {
	ctxt.Cursym = s

	firstp := ctxt.NewProg()
	lastp := firstp
	xfol(ctxt, s.Text, &lastp)
	lastp.Link = nil
	s.Text = firstp.Link
}

func nofollow(a int) bool {
	switch a {
	case obj.AJMP,
		obj.ARET,
		AIRETL,
		AIRETQ,
		AIRETW,
		ARETFL,
		ARETFQ,
		ARETFW,
		obj.AUNDEF:
		return true
	}

	return false
}

func pushpop(a int) bool {
	switch a {
	case APUSHL,
		APUSHFL,
		APUSHQ,
		APUSHFQ,
		APUSHW,
		APUSHFW,
		APOPL,
		APOPFL,
		APOPQ,
		APOPFQ,
		APOPW,
		APOPFW:
		return true
	}

	return false
}

func relinv(a int16) int16 {
	switch a {
	case AJEQ:
		return AJNE
	case AJNE:
		return AJEQ
	case AJLE:
		return AJGT
	case AJLS:
		return AJHI
	case AJLT:
		return AJGE
	case AJMI:
		return AJPL
	case AJGE:
		return AJLT
	case AJPL:
		return AJMI
	case AJGT:
		return AJLE
	case AJHI:
		return AJLS
	case AJCS:
		return AJCC
	case AJCC:
		return AJCS
	case AJPS:
		return AJPC
	case AJPC:
		return AJPS
	case AJOS:
		return AJOC
	case AJOC:
		return AJOS
	}

	log.Fatalf("unknown relation: %s", obj.Aconv(int(a)))
	return 0
}

func xfol(ctxt *obj.Link, p *obj.Prog, last **obj.Prog) {
	var q *obj.Prog
	var i int
	var a int

loop:
	if p == nil {
		return
	}
	if p.As == obj.AJMP {
		q = p.Pcond
		if q != nil && q.As != obj.ATEXT {
			/* mark instruction as done and continue layout at target of jump */
			p.Mark = 1

			p = q
			if p.Mark == 0 {
				goto loop
			}
		}
	}

	if p.Mark != 0 {
		/*
		 * p goes here, but already used it elsewhere.
		 * copy up to 4 instructions or else branch to other copy.
		 */
		i = 0
		q = p
		for ; i < 4; i, q = i+1, q.Link {
			if q == nil {
				break
			}
			if q == *last {
				break
			}
			a = int(q.As)
			if a == obj.ANOP {
				i--
				continue
			}

			if nofollow(a) || pushpop(a) {
				break // NOTE(rsc): arm does goto copy
			}
			if q.Pcond == nil || q.Pcond.Mark != 0 {
				continue
			}
			if a == obj.ACALL || a == ALOOP {
				continue
			}
			for {
				if p.As == obj.ANOP {
					p = p.Link
					continue
				}

				q = obj.Copyp(ctxt, p)
				p = p.Link
				q.Mark = 1
				(*last).Link = q
				*last = q
				if int(q.As) != a || q.Pcond == nil || q.Pcond.Mark != 0 {
					continue
				}

				q.As = relinv(q.As)
				p = q.Pcond
				q.Pcond = q.Link
				q.Link = p
				xfol(ctxt, q.Link, last)
				p = q.Link
				if p.Mark != 0 {
					return
				}
				goto loop
				/* */
			}
		}
		q = ctxt.NewProg()
		q.As = obj.AJMP
		q.Lineno = p.Lineno
		q.To.Type = obj.TYPE_BRANCH
		q.To.Offset = p.Pc
		q.Pcond = p
		p = q
	}

	/* emit p */
	p.Mark = 1

	(*last).Link = p
	*last = p
	a = int(p.As)

	/* continue loop with what comes after p */
	if nofollow(a) {
		return
	}
	if p.Pcond != nil && a != obj.ACALL {
		/*
		 * some kind of conditional branch.
		 * recurse to follow one path.
		 * continue loop on the other.
		 */
		q = obj.Brchain(ctxt, p.Pcond)
		if q != nil {
			p.Pcond = q
		}
		q = obj.Brchain(ctxt, p.Link)
		if q != nil {
			p.Link = q
		}
		if p.From.Type == obj.TYPE_CONST {
			if p.From.Offset == 1 {
				/*
				 * expect conditional jump to be taken.
				 * rewrite so that's the fall-through case.
				 */
				p.As = relinv(int16(a))

				q = p.Link
				p.Link = p.Pcond
				p.Pcond = q
			}
		} else {
			q = p.Link
			if q.Mark != 0 {
				if a != ALOOP {
					p.As = relinv(int16(a))
					p.Link = p.Pcond
					p.Pcond = q
				}
			}
		}

		xfol(ctxt, p.Link, last)
		if p.Pcond.Mark != 0 {
			return
		}
		p = p.Pcond
		goto loop
	}

	p = p.Link
	goto loop
}

var unaryDst = map[int]bool{
	ABSWAPL:    true,
	ABSWAPQ:    true,
	ACMPXCHG8B: true,
	ADECB:      true,
	ADECL:      true,
	ADECQ:      true,
	ADECW:      true,
	AINCB:      true,
	AINCL:      true,
	AINCQ:      true,
	AINCW:      true,
	ANEGB:      true,
	ANEGL:      true,
	ANEGQ:      true,
	ANEGW:      true,
	ANOTB:      true,
	ANOTL:      true,
	ANOTQ:      true,
	ANOTW:      true,
	APOPL:      true,
	APOPQ:      true,
	APOPW:      true,
	ASETCC:     true,
	ASETCS:     true,
	ASETEQ:     true,
	ASETGE:     true,
	ASETGT:     true,
	ASETHI:     true,
	ASETLE:     true,
	ASETLS:     true,
	ASETLT:     true,
	ASETMI:     true,
	ASETNE:     true,
	ASETOC:     true,
	ASETOS:     true,
	ASETPC:     true,
	ASETPL:     true,
	ASETPS:     true,
	AFFREE:     true,
	AFLDENV:    true,
	AFSAVE:     true,
	AFSTCW:     true,
	AFSTENV:    true,
	AFSTSW:     true,
	AFXSAVE:    true,
	AFXSAVE64:  true,
	ASTMXCSR:   true,
}

var Linkamd64 = obj.LinkArch{
	ByteOrder:  binary.LittleEndian,
	Name:       "amd64",
	Thechar:    '6',
	Preprocess: preprocess,
	Assemble:   span6,
	Follow:     follow,
	Progedit:   progedit,
	UnaryDst:   unaryDst,
	Minlc:      1,
	Ptrsize:    8,
	Regsize:    8,
}

var Linkamd64p32 = obj.LinkArch{
	ByteOrder:  binary.LittleEndian,
	Name:       "amd64p32",
	Thechar:    '6',
	Preprocess: preprocess,
	Assemble:   span6,
	Follow:     follow,
	Progedit:   progedit,
	UnaryDst:   unaryDst,
	Minlc:      1,
	Ptrsize:    4,
	Regsize:    8,
}

var Link386 = obj.LinkArch{
	ByteOrder:  binary.LittleEndian,
	Name:       "386",
	Thechar:    '8',
	Preprocess: preprocess,
	Assemble:   span6,
	Follow:     follow,
	Progedit:   progedit,
	UnaryDst:   unaryDst,
	Minlc:      1,
	Ptrsize:    4,
	Regsize:    4,
}
Пример #8
0
func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
	ctxt.Cursym = cursym

	if cursym.Text == nil || cursym.Text.Link == nil {
		return
	}

	p := cursym.Text
	textstksiz := p.To.Offset
	aoffset := int32(textstksiz)

	cursym.Args = p.To.Val.(int32)
	cursym.Locals = int32(textstksiz)

	/*
	 * find leaf subroutines
	 * strip NOPs
	 * expand RET
	 */
	ctxt.Bso.Flush()
	q := (*obj.Prog)(nil)
	var q1 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		switch p.As {
		case obj.ATEXT:
			p.Mark |= LEAF

		case obj.ARET:
			break

		case obj.ANOP:
			q1 = p.Link
			q.Link = q1 /* q is non-nop */
			q1.Mark |= p.Mark
			continue

		case ABL,
			obj.ADUFFZERO,
			obj.ADUFFCOPY:
			cursym.Text.Mark &^= LEAF
			fallthrough

		case ACBNZ,
			ACBZ,
			ACBNZW,
			ACBZW,
			ATBZ,
			ATBNZ,
			AB,
			ABEQ,
			ABNE,
			ABCS,
			ABHS,
			ABCC,
			ABLO,
			ABMI,
			ABPL,
			ABVS,
			ABVC,
			ABHI,
			ABLS,
			ABGE,
			ABLT,
			ABGT,
			ABLE,
			AADR, /* strange */
			AADRP:
			q1 = p.Pcond

			if q1 != nil {
				for q1.As == obj.ANOP {
					q1 = q1.Link
					p.Pcond = q1
				}
			}

			break
		}

		q = p
	}

	var o int
	var q2 *obj.Prog
	var retjmp *obj.LSym
	for p := cursym.Text; p != nil; p = p.Link {
		o = int(p.As)
		switch o {
		case obj.ATEXT:
			cursym.Text = p
			if textstksiz < 0 {
				ctxt.Autosize = 0
			} else {
				ctxt.Autosize = int32(textstksiz + 8)
			}
			if (cursym.Text.Mark&LEAF != 0) && ctxt.Autosize <= 8 {
				ctxt.Autosize = 0
			} else if ctxt.Autosize&(16-1) != 0 {
				// The frame includes an LR.
				// If the frame size is 8, it's only an LR,
				// so there's no potential for breaking references to
				// local variables by growing the frame size,
				// because there are no local variables.
				// But otherwise, if there is a non-empty locals section,
				// the author of the code is responsible for making sure
				// that the frame size is 8 mod 16.
				if ctxt.Autosize == 8 {
					ctxt.Autosize += 8
					cursym.Locals += 8
				} else {
					ctxt.Diag("%v: unaligned frame size %d - must be 8 mod 16 (or 0)", p, ctxt.Autosize-8)
				}
			}
			p.To.Offset = int64(ctxt.Autosize) - 8
			if ctxt.Autosize == 0 && !(cursym.Text.Mark&LEAF != 0) {
				if ctxt.Debugvlog != 0 {
					fmt.Fprintf(ctxt.Bso, "save suppressed in: %s\n", cursym.Text.From.Sym.Name)
				}
				ctxt.Bso.Flush()
				cursym.Text.Mark |= LEAF
			}

			if !(p.From3.Offset&obj.NOSPLIT != 0) {
				p = stacksplit(ctxt, p, ctxt.Autosize) // emit split check
			}

			aoffset = ctxt.Autosize
			if aoffset > 0xF0 {
				aoffset = 0xF0
			}
			if cursym.Text.Mark&LEAF != 0 {
				cursym.Leaf = 1
				if ctxt.Autosize == 0 {
					break
				}
				aoffset = 0
			}

			q = p
			if ctxt.Autosize > aoffset {
				q = ctxt.NewProg()
				q.As = ASUB
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(ctxt.Autosize) - int64(aoffset)
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REGSP
				q.Spadj = int32(q.From.Offset)
				q.Link = p.Link
				p.Link = q
				if cursym.Text.Mark&LEAF != 0 {
					break
				}
			}

			q1 = ctxt.NewProg()
			q1.As = AMOVD
			q1.Lineno = p.Lineno
			q1.From.Type = obj.TYPE_REG
			q1.From.Reg = REGLINK
			q1.To.Type = obj.TYPE_MEM
			q1.Scond = C_XPRE
			q1.To.Offset = int64(-aoffset)
			q1.To.Reg = REGSP
			q1.Link = q.Link
			q1.Spadj = aoffset
			q.Link = q1

			if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
				//
				//	MOV g_panic(g), R1
				//	CMP ZR, R1
				//	BEQ end
				//	MOV panic_argp(R1), R2
				//	ADD $(autosize+8), RSP, R3
				//	CMP R2, R3
				//	BNE end
				//	ADD $8, RSP, R4
				//	MOVD R4, panic_argp(R1)
				// end:
				//	NOP
				//
				// The NOP is needed to give the jumps somewhere to land.
				// It is a liblink NOP, not a ARM64 NOP: it encodes to 0 instruction bytes.
				q = q1

				q = obj.Appendp(ctxt, q)
				q.As = AMOVD
				q.From.Type = obj.TYPE_MEM
				q.From.Reg = REGG
				q.From.Offset = 4 * int64(ctxt.Arch.Ptrsize) // G.panic
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R1

				q = obj.Appendp(ctxt, q)
				q.As = ACMP
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REGZERO
				q.Reg = REG_R1

				q = obj.Appendp(ctxt, q)
				q.As = ABEQ
				q.To.Type = obj.TYPE_BRANCH
				q1 = q

				q = obj.Appendp(ctxt, q)
				q.As = AMOVD
				q.From.Type = obj.TYPE_MEM
				q.From.Reg = REG_R1
				q.From.Offset = 0 // Panic.argp
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R2

				q = obj.Appendp(ctxt, q)
				q.As = AADD
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(ctxt.Autosize) + 8
				q.Reg = REGSP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R3

				q = obj.Appendp(ctxt, q)
				q.As = ACMP
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R2
				q.Reg = REG_R3

				q = obj.Appendp(ctxt, q)
				q.As = ABNE
				q.To.Type = obj.TYPE_BRANCH
				q2 = q

				q = obj.Appendp(ctxt, q)
				q.As = AADD
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = 8
				q.Reg = REGSP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R4

				q = obj.Appendp(ctxt, q)
				q.As = AMOVD
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R4
				q.To.Type = obj.TYPE_MEM
				q.To.Reg = REG_R1
				q.To.Offset = 0 // Panic.argp

				q = obj.Appendp(ctxt, q)

				q.As = obj.ANOP
				q1.Pcond = q
				q2.Pcond = q
			}

		case obj.ARET:
			nocache(p)
			if p.From.Type == obj.TYPE_CONST {
				ctxt.Diag("using BECOME (%v) is not supported!", p)
				break
			}

			retjmp = p.To.Sym
			p.To = obj.Addr{}
			if cursym.Text.Mark&LEAF != 0 {
				if ctxt.Autosize != 0 {
					p.As = AADD
					p.From.Type = obj.TYPE_CONST
					p.From.Offset = int64(ctxt.Autosize)
					p.To.Type = obj.TYPE_REG
					p.To.Reg = REGSP
					p.Spadj = -ctxt.Autosize
				}
			} else {
				/* want write-back pre-indexed SP+autosize -> SP, loading REGLINK*/
				aoffset = ctxt.Autosize

				if aoffset > 0xF0 {
					aoffset = 0xF0
				}
				p.As = AMOVD
				p.From.Type = obj.TYPE_MEM
				p.Scond = C_XPOST
				p.From.Offset = int64(aoffset)
				p.From.Reg = REGSP
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REGLINK
				p.Spadj = -aoffset
				if ctxt.Autosize > aoffset {
					q = ctxt.NewProg()
					q.As = AADD
					q.From.Type = obj.TYPE_CONST
					q.From.Offset = int64(ctxt.Autosize) - int64(aoffset)
					q.To.Type = obj.TYPE_REG
					q.To.Reg = REGSP
					q.Link = p.Link
					q.Spadj = int32(-q.From.Offset)
					q.Lineno = p.Lineno
					p.Link = q
					p = q
				}
			}

			if p.As != obj.ARET {
				q = ctxt.NewProg()
				q.Lineno = p.Lineno
				q.Link = p.Link
				p.Link = q
				p = q
			}

			if retjmp != nil { // retjmp
				p.As = AB
				p.To.Type = obj.TYPE_BRANCH
				p.To.Sym = retjmp
				p.Spadj = +ctxt.Autosize
				break
			}

			p.As = obj.ARET
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = 0
			p.To.Reg = REGLINK
			p.Spadj = +ctxt.Autosize

		case AADD, ASUB:
			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
				if p.As == AADD {
					p.Spadj = int32(-p.From.Offset)
				} else {
					p.Spadj = int32(+p.From.Offset)
				}
			}
			break
		}
	}
}
Пример #9
0
// Rewrite p, if necessary, to access global data via the global offset table.
func rewriteToUseGot(ctxt *obj.Link, p *obj.Prog) {
	var add, lea, mov, reg int16
	if p.Mode == 64 {
		add = AADDQ
		lea = ALEAQ
		mov = AMOVQ
		reg = REG_R15
	} else {
		add = AADDL
		lea = ALEAL
		mov = AMOVL
		reg = REG_CX
	}

	if p.As == obj.ADUFFCOPY || p.As == obj.ADUFFZERO {
		//     ADUFFxxx $offset
		// becomes
		//     $MOV runtime.duffxxx@GOT, $reg
		//     $ADD $offset, $reg
		//     CALL $reg
		var sym *obj.LSym
		if p.As == obj.ADUFFZERO {
			sym = obj.Linklookup(ctxt, "runtime.duffzero", 0)
		} else {
			sym = obj.Linklookup(ctxt, "runtime.duffcopy", 0)
		}
		offset := p.To.Offset
		p.As = mov
		p.From.Type = obj.TYPE_MEM
		p.From.Name = obj.NAME_GOTREF
		p.From.Sym = sym
		p.To.Type = obj.TYPE_REG
		p.To.Reg = reg
		p.To.Offset = 0
		p.To.Sym = nil
		p1 := obj.Appendp(ctxt, p)
		p1.As = add
		p1.From.Type = obj.TYPE_CONST
		p1.From.Offset = offset
		p1.To.Type = obj.TYPE_REG
		p1.To.Reg = reg
		p2 := obj.Appendp(ctxt, p1)
		p2.As = obj.ACALL
		p2.To.Type = obj.TYPE_REG
		p2.To.Reg = reg
	}

	// We only care about global data: NAME_EXTERN means a global
	// symbol in the Go sense, and p.Sym.Local is true for a few
	// internally defined symbols.
	if p.As == lea && p.From.Type == obj.TYPE_MEM && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
		// $LEA sym, Rx becomes $MOV $sym, Rx which will be rewritten below
		p.As = mov
		p.From.Type = obj.TYPE_ADDR
	}
	if p.From.Type == obj.TYPE_ADDR && p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
		// $MOV $sym, Rx becomes $MOV sym@GOT, Rx
		// $MOV $sym+<off>, Rx becomes $MOV sym@GOT, Rx; $ADD <off>, Rx
		// On 386 only, more complicated things like PUSHL $sym become $MOV sym@GOT, CX; PUSHL CX
		cmplxdest := false
		pAs := p.As
		var dest obj.Addr
		if p.To.Type != obj.TYPE_REG || pAs != mov {
			if p.Mode == 64 {
				ctxt.Diag("do not know how to handle LEA-type insn to non-register in %v with -dynlink", p)
			}
			cmplxdest = true
			dest = p.To
			p.As = mov
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REG_CX
			p.To.Sym = nil
			p.To.Name = obj.NAME_NONE
		}
		p.From.Type = obj.TYPE_MEM
		p.From.Name = obj.NAME_GOTREF
		q := p
		if p.From.Offset != 0 {
			q = obj.Appendp(ctxt, p)
			q.As = add
			q.From.Type = obj.TYPE_CONST
			q.From.Offset = p.From.Offset
			q.To = p.To
			p.From.Offset = 0
		}
		if cmplxdest {
			q = obj.Appendp(ctxt, q)
			q.As = pAs
			q.To = dest
			q.From.Type = obj.TYPE_REG
			q.From.Reg = REG_CX
		}
	}
	if p.From3 != nil && p.From3.Name == obj.NAME_EXTERN {
		ctxt.Diag("don't know how to handle %v with -dynlink", p)
	}
	var source *obj.Addr
	// MOVx sym, Ry becomes $MOV sym@GOT, R15; MOVx (R15), Ry
	// MOVx Ry, sym becomes $MOV sym@GOT, R15; MOVx Ry, (R15)
	// An addition may be inserted between the two MOVs if there is an offset.
	if p.From.Name == obj.NAME_EXTERN && !p.From.Sym.Local {
		if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
			ctxt.Diag("cannot handle NAME_EXTERN on both sides in %v with -dynlink", p)
		}
		source = &p.From
	} else if p.To.Name == obj.NAME_EXTERN && !p.To.Sym.Local {
		source = &p.To
	} else {
		return
	}
	if p.As == obj.ACALL {
		// When dynlinking on 386, almost any call might end up being a call
		// to a PLT, so make sure the GOT pointer is loaded into BX.
		// RegTo2 is set on the replacement call insn to stop it being
		// processed when it is in turn passed to progedit.
		if p.Mode == 64 || (p.To.Sym != nil && p.To.Sym.Local) || p.RegTo2 != 0 {
			return
		}
		p1 := obj.Appendp(ctxt, p)
		p2 := obj.Appendp(ctxt, p1)

		p1.As = ALEAL
		p1.From.Type = obj.TYPE_MEM
		p1.From.Name = obj.NAME_STATIC
		p1.From.Sym = obj.Linklookup(ctxt, "_GLOBAL_OFFSET_TABLE_", 0)
		p1.To.Type = obj.TYPE_REG
		p1.To.Reg = REG_BX

		p2.As = p.As
		p2.Scond = p.Scond
		p2.From = p.From
		p2.From3 = p.From3
		p2.Reg = p.Reg
		p2.To = p.To
		// p.To.Type was set to TYPE_BRANCH above, but that makes checkaddr
		// in ../pass.go complain, so set it back to TYPE_MEM here, until p2
		// itself gets passed to progedit.
		p2.To.Type = obj.TYPE_MEM
		p2.RegTo2 = 1

		obj.Nopout(p)
		return

	}
	if p.As == obj.ATEXT || p.As == obj.AFUNCDATA || p.As == obj.ARET || p.As == obj.AJMP {
		return
	}
	if source.Type != obj.TYPE_MEM {
		ctxt.Diag("don't know how to handle %v with -dynlink", p)
	}
	p1 := obj.Appendp(ctxt, p)
	p2 := obj.Appendp(ctxt, p1)

	p1.As = mov
	p1.From.Type = obj.TYPE_MEM
	p1.From.Sym = source.Sym
	p1.From.Name = obj.NAME_GOTREF
	p1.To.Type = obj.TYPE_REG
	p1.To.Reg = reg

	p2.As = p.As
	p2.From = p.From
	p2.To = p.To
	if p.From.Name == obj.NAME_EXTERN {
		p2.From.Reg = reg
		p2.From.Name = obj.NAME_NONE
		p2.From.Sym = nil
	} else if p.To.Name == obj.NAME_EXTERN {
		p2.To.Reg = reg
		p2.To.Name = obj.NAME_NONE
		p2.To.Sym = nil
	} else {
		return
	}
	obj.Nopout(p)
}
Пример #10
0
func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
	// MOV	g_stackguard(g), R1
	p = obj.Appendp(ctxt, p)

	p.As = AMOVD
	p.From.Type = obj.TYPE_MEM
	p.From.Reg = REGG
	p.From.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
	if ctxt.Cursym.Cfunc != 0 {
		p.From.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
	}
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R1

	q := (*obj.Prog)(nil)
	if framesize <= obj.StackSmall {
		// small stack: SP < stackguard
		//	MOV	SP, R2
		//	CMP	stackguard, R2
		p = obj.Appendp(ctxt, p)

		p.As = AMOVD
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.Reg = REG_R2
	} else if framesize <= obj.StackBig {
		// large stack: SP-framesize < stackguard-StackSmall
		//	SUB	$framesize, SP, R2
		//	CMP	stackguard, R2
		p = obj.Appendp(ctxt, p)

		p.As = ASUB
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(framesize)
		p.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.Reg = REG_R2
	} else {
		// Such a large stack we need to protect against wraparound
		// if SP is close to zero.
		//	SP-stackguard+StackGuard < framesize + (StackGuard-StackSmall)
		// The +StackGuard on both sides is required to keep the left side positive:
		// SP is allowed to be slightly below stackguard. See stack.h.
		//	CMP	$StackPreempt, R1
		//	BEQ	label_of_call_to_morestack
		//	ADD	$StackGuard, SP, R2
		//	SUB	R1, R2
		//	MOV	$(framesize+(StackGuard-StackSmall)), R3
		//	CMP	R3, R2
		p = obj.Appendp(ctxt, p)

		p.As = ACMP
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = obj.StackPreempt
		p.Reg = REG_R1

		p = obj.Appendp(ctxt, p)
		q = p
		p.As = ABEQ
		p.To.Type = obj.TYPE_BRANCH

		p = obj.Appendp(ctxt, p)
		p.As = AADD
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = obj.StackGuard
		p.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = ASUB
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = AMOVD
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(framesize) + (obj.StackGuard - obj.StackSmall)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R3

		p = obj.Appendp(ctxt, p)
		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R3
		p.Reg = REG_R2
	}

	// BLS	do-morestack
	bls := obj.Appendp(ctxt, p)
	bls.As = ABLS
	bls.To.Type = obj.TYPE_BRANCH

	var last *obj.Prog
	for last = ctxt.Cursym.Text; last.Link != nil; last = last.Link {
	}

	spfix := obj.Appendp(ctxt, last)
	spfix.As = obj.ANOP
	spfix.Spadj = -framesize

	// MOV	LR, R3
	movlr := obj.Appendp(ctxt, spfix)
	movlr.As = AMOVD
	movlr.From.Type = obj.TYPE_REG
	movlr.From.Reg = REGLINK
	movlr.To.Type = obj.TYPE_REG
	movlr.To.Reg = REG_R3
	if q != nil {
		q.Pcond = movlr
	}
	bls.Pcond = movlr

	debug := movlr
	if false {
		debug = obj.Appendp(ctxt, debug)
		debug.As = AMOVD
		debug.From.Type = obj.TYPE_CONST
		debug.From.Offset = int64(framesize)
		debug.To.Type = obj.TYPE_REG
		debug.To.Reg = REGTMP
	}

	// BL	runtime.morestack(SB)
	call := obj.Appendp(ctxt, debug)
	call.As = ABL
	call.To.Type = obj.TYPE_BRANCH
	morestack := "runtime.morestack"
	switch {
	case ctxt.Cursym.Cfunc != 0:
		morestack = "runtime.morestackc"
	case ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0:
		morestack = "runtime.morestack_noctxt"
	}
	call.To.Sym = obj.Linklookup(ctxt, morestack, 0)

	// B	start
	jmp := obj.Appendp(ctxt, call)
	jmp.As = AB
	jmp.To.Type = obj.TYPE_BRANCH
	jmp.Pcond = ctxt.Cursym.Text.Link
	jmp.Spadj = +framesize

	// placeholder for bls's jump target
	// p = obj.Appendp(ctxt, p)
	// p.As = obj.ANOP

	return bls
}
Пример #11
0
func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
	// MOVV	g_stackguard(g), R1
	p = obj.Appendp(ctxt, p)

	p.As = AMOVV
	p.From.Type = obj.TYPE_MEM
	p.From.Reg = REGG
	p.From.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
	if ctxt.Cursym.Cfunc != 0 {
		p.From.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
	}
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R1

	var q *obj.Prog
	if framesize <= obj.StackSmall {
		// small stack: SP < stackguard
		//	AGTU	SP, stackguard, R1
		p = obj.Appendp(ctxt, p)

		p.As = ASGTU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REGSP
		p.Reg = REG_R1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R1
	} else if framesize <= obj.StackBig {
		// large stack: SP-framesize < stackguard-StackSmall
		//	ADDV	$-framesize, SP, R2
		//	SGTU	R2, stackguard, R1
		p = obj.Appendp(ctxt, p)

		p.As = AADDV
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(-framesize)
		p.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = ASGTU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R2
		p.Reg = REG_R1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R1
	} else {
		// Such a large stack we need to protect against wraparound.
		// If SP is close to zero:
		//	SP-stackguard+StackGuard <= framesize + (StackGuard-StackSmall)
		// The +StackGuard on both sides is required to keep the left side positive:
		// SP is allowed to be slightly below stackguard. See stack.h.
		//
		// Preemption sets stackguard to StackPreempt, a very large value.
		// That breaks the math above, so we have to check for that explicitly.
		//	// stackguard is R1
		//	MOVV	$StackPreempt, R2
		//	BEQ	R1, R2, label-of-call-to-morestack
		//	ADDV	$StackGuard, SP, R2
		//	SUBVU	R1, R2
		//	MOVV	$(framesize+(StackGuard-StackSmall)), R1
		//	SGTU	R2, R1, R1
		p = obj.Appendp(ctxt, p)

		p.As = AMOVV
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = obj.StackPreempt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		q = p
		p.As = ABEQ
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.Reg = REG_R2
		p.To.Type = obj.TYPE_BRANCH
		p.Mark |= BRANCH

		p = obj.Appendp(ctxt, p)
		p.As = AADDV
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = obj.StackGuard
		p.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = ASUBVU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R2

		p = obj.Appendp(ctxt, p)
		p.As = AMOVV
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(framesize) + obj.StackGuard - obj.StackSmall
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R1

		p = obj.Appendp(ctxt, p)
		p.As = ASGTU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R2
		p.Reg = REG_R1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R1
	}

	// q1: BNE	R1, done
	p = obj.Appendp(ctxt, p)
	q1 := p

	p.As = ABNE
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REG_R1
	p.To.Type = obj.TYPE_BRANCH
	p.Mark |= BRANCH

	// MOVV	LINK, R3
	p = obj.Appendp(ctxt, p)

	p.As = AMOVV
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REGLINK
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R3
	if q != nil {
		q.Pcond = p
		p.Mark |= LABEL
	}

	// JAL	runtime.morestack(SB)
	p = obj.Appendp(ctxt, p)

	p.As = AJAL
	p.To.Type = obj.TYPE_BRANCH
	if ctxt.Cursym.Cfunc != 0 {
		p.To.Sym = obj.Linklookup(ctxt, "runtime.morestackc", 0)
	} else if ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0 {
		p.To.Sym = obj.Linklookup(ctxt, "runtime.morestack_noctxt", 0)
	} else {
		p.To.Sym = obj.Linklookup(ctxt, "runtime.morestack", 0)
	}
	p.Mark |= BRANCH

	// JMP	start
	p = obj.Appendp(ctxt, p)

	p.As = AJMP
	p.To.Type = obj.TYPE_BRANCH
	p.Pcond = ctxt.Cursym.Text.Link
	p.Mark |= BRANCH

	// placeholder for q1's jump target
	p = obj.Appendp(ctxt, p)

	p.As = obj.ANOP // zero-width place holder
	q1.Pcond = p

	return p
}
Пример #12
0
func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
	// TODO(minux): add morestack short-cuts with small fixed frame-size.
	ctxt.Cursym = cursym

	// a switch for enabling/disabling instruction scheduling
	nosched := true

	if cursym.Text == nil || cursym.Text.Link == nil {
		return
	}

	p := cursym.Text
	textstksiz := p.To.Offset

	cursym.Args = p.To.Val.(int32)
	cursym.Locals = int32(textstksiz)

	/*
	 * find leaf subroutines
	 * strip NOPs
	 * expand RET
	 * expand BECOME pseudo
	 */
	if ctxt.Debugvlog != 0 {
		fmt.Fprintf(ctxt.Bso, "%5.2f noops\n", obj.Cputime())
	}
	ctxt.Bso.Flush()

	var q *obj.Prog
	var q1 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		switch p.As {
		/* too hard, just leave alone */
		case obj.ATEXT:
			q = p

			p.Mark |= LABEL | LEAF | SYNC
			if p.Link != nil {
				p.Link.Mark |= LABEL
			}

		/* too hard, just leave alone */
		case AMOVW,
			AMOVV:
			q = p
			if p.To.Type == obj.TYPE_REG && p.To.Reg >= REG_SPECIAL {
				p.Mark |= LABEL | SYNC
				break
			}
			if p.From.Type == obj.TYPE_REG && p.From.Reg >= REG_SPECIAL {
				p.Mark |= LABEL | SYNC
			}

		/* too hard, just leave alone */
		case ASYSCALL,
			AWORD,
			ATLBWR,
			ATLBWI,
			ATLBP,
			ATLBR:
			q = p
			p.Mark |= LABEL | SYNC

		case ANOR:
			q = p
			if p.To.Type == obj.TYPE_REG {
				if p.To.Reg == REGZERO {
					p.Mark |= LABEL | SYNC
				}
			}

		case ABGEZAL,
			ABLTZAL,
			AJAL,
			obj.ADUFFZERO,
			obj.ADUFFCOPY:
			cursym.Text.Mark &^= LEAF
			fallthrough

		case AJMP,
			ABEQ,
			ABGEZ,
			ABGTZ,
			ABLEZ,
			ABLTZ,
			ABNE,
			ABFPT, ABFPF:
			if p.As == ABFPT || p.As == ABFPF {
				// We don't treat ABFPT and ABFPF as branches here,
				// so that we will always fill nop (0x0) in their
				// delay slot during assembly.
				// This is to workaround a kernel FPU emulator bug
				// where it uses the user stack to simulate the
				// instruction in the delay slot if it's not 0x0,
				// and somehow that leads to SIGSEGV when the kernel
				// jump to the stack.
				p.Mark |= SYNC
			} else {
				p.Mark |= BRANCH
			}
			q = p
			q1 = p.Pcond
			if q1 != nil {
				for q1.As == obj.ANOP {
					q1 = q1.Link
					p.Pcond = q1
				}

				if q1.Mark&LEAF == 0 {
					q1.Mark |= LABEL
				}
			}
			//else {
			//	p.Mark |= LABEL
			//}
			q1 = p.Link
			if q1 != nil {
				q1.Mark |= LABEL
			}
			continue

		case ARET:
			q = p
			if p.Link != nil {
				p.Link.Mark |= LABEL
			}
			continue

		case obj.ANOP:
			q1 = p.Link
			q.Link = q1 /* q is non-nop */
			q1.Mark |= p.Mark
			continue

		default:
			q = p
			continue
		}
	}

	autosize := int32(0)
	var o int
	var p1 *obj.Prog
	var p2 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		o = int(p.As)
		switch o {
		case obj.ATEXT:
			autosize = int32(textstksiz + 8)
			if (p.Mark&LEAF != 0) && autosize <= 8 {
				autosize = 0
			} else if autosize&4 != 0 {
				autosize += 4
			}
			p.To.Offset = int64(autosize) - 8

			if p.From3.Offset&obj.NOSPLIT == 0 {
				p = stacksplit(ctxt, p, autosize) // emit split check
			}

			q = p

			if autosize != 0 {
				q = obj.Appendp(ctxt, p)
				q.As = AADDV
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(-autosize)
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REGSP
				q.Spadj = +autosize
			} else if cursym.Text.Mark&LEAF == 0 {
				if cursym.Text.From3.Offset&obj.NOSPLIT != 0 {
					if ctxt.Debugvlog != 0 {
						fmt.Fprintf(ctxt.Bso, "save suppressed in: %s\n", cursym.Name)
						ctxt.Bso.Flush()
					}

					cursym.Text.Mark |= LEAF
				}
			}

			if cursym.Text.Mark&LEAF != 0 {
				cursym.Leaf = 1
				break
			}

			q = obj.Appendp(ctxt, q)
			q.As = AMOVV
			q.Lineno = p.Lineno
			q.From.Type = obj.TYPE_REG
			q.From.Reg = REGLINK
			q.To.Type = obj.TYPE_MEM
			q.To.Offset = int64(0)
			q.To.Reg = REGSP

			if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
				//
				//	MOVV	g_panic(g), R1
				//	BEQ		R1, end
				//	MOVV	panic_argp(R1), R2
				//	ADDV	$(autosize+8), R29, R3
				//	BNE		R2, R3, end
				//	ADDV	$8, R29, R2
				//	MOVV	R2, panic_argp(R1)
				// end:
				//	NOP
				//
				// The NOP is needed to give the jumps somewhere to land.
				// It is a liblink NOP, not an mips NOP: it encodes to 0 instruction bytes.

				q = obj.Appendp(ctxt, q)

				q.As = AMOVV
				q.From.Type = obj.TYPE_MEM
				q.From.Reg = REGG
				q.From.Offset = 4 * int64(ctxt.Arch.Ptrsize) // G.panic
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R1

				q = obj.Appendp(ctxt, q)
				q.As = ABEQ
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R1
				q.To.Type = obj.TYPE_BRANCH
				q.Mark |= BRANCH
				p1 = q

				q = obj.Appendp(ctxt, q)
				q.As = AMOVV
				q.From.Type = obj.TYPE_MEM
				q.From.Reg = REG_R1
				q.From.Offset = 0 // Panic.argp
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R2

				q = obj.Appendp(ctxt, q)
				q.As = AADDV
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(autosize) + 8
				q.Reg = REGSP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R3

				q = obj.Appendp(ctxt, q)
				q.As = ABNE
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R2
				q.Reg = REG_R3
				q.To.Type = obj.TYPE_BRANCH
				q.Mark |= BRANCH
				p2 = q

				q = obj.Appendp(ctxt, q)
				q.As = AADDV
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = 8
				q.Reg = REGSP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R2

				q = obj.Appendp(ctxt, q)
				q.As = AMOVV
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R2
				q.To.Type = obj.TYPE_MEM
				q.To.Reg = REG_R1
				q.To.Offset = 0 // Panic.argp

				q = obj.Appendp(ctxt, q)

				q.As = obj.ANOP
				p1.Pcond = q
				p2.Pcond = q
			}

		case ARET:
			if p.From.Type == obj.TYPE_CONST {
				ctxt.Diag("using BECOME (%v) is not supported!", p)
				break
			}

			if p.To.Sym != nil { // retjmp
				p.As = AJMP
				p.To.Type = obj.TYPE_BRANCH
				break
			}

			if cursym.Text.Mark&LEAF != 0 {
				if autosize == 0 {
					p.As = AJMP
					p.From = obj.Addr{}
					p.To.Type = obj.TYPE_MEM
					p.To.Offset = 0
					p.To.Reg = REGLINK
					p.Mark |= BRANCH
					break
				}

				p.As = AADDV
				p.From.Type = obj.TYPE_CONST
				p.From.Offset = int64(autosize)
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REGSP
				p.Spadj = -autosize

				q = ctxt.NewProg()
				q.As = AJMP
				q.Lineno = p.Lineno
				q.To.Type = obj.TYPE_MEM
				q.To.Offset = 0
				q.To.Reg = REGLINK
				q.Mark |= BRANCH
				q.Spadj = +autosize

				q.Link = p.Link
				p.Link = q
				break
			}

			p.As = AMOVV
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = 0
			p.From.Reg = REGSP
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REG_R4

			if false {
				// Debug bad returns
				q = ctxt.NewProg()

				q.As = AMOVV
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_MEM
				q.From.Offset = 0
				q.From.Reg = REG_R4
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REGTMP

				q.Link = p.Link
				p.Link = q
				p = q
			}

			if autosize != 0 {
				q = ctxt.NewProg()
				q.As = AADDV
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(autosize)
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REGSP
				q.Spadj = -autosize

				q.Link = p.Link
				p.Link = q
			}

			q1 = ctxt.NewProg()
			q1.As = AJMP
			q1.Lineno = p.Lineno
			q1.To.Type = obj.TYPE_MEM
			q1.To.Offset = 0
			q1.To.Reg = REG_R4
			q1.Mark |= BRANCH
			q1.Spadj = +autosize

			q1.Link = q.Link
			q.Link = q1

		case AADDV,
			AADDVU:
			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
				p.Spadj = int32(-p.From.Offset)
			}
		}
	}

	if nosched {
		// if we don't do instruction scheduling, simply add
		// NOP after each branch instruction.
		for p = cursym.Text; p != nil; p = p.Link {
			if p.Mark&BRANCH != 0 {
				addnop(ctxt, p)
			}
		}
		return
	}

	// instruction scheduling
	q = nil          // p - 1
	q1 = cursym.Text // top of block
	o = 0            // count of instructions
	for p = cursym.Text; p != nil; p = p1 {
		p1 = p.Link
		o++
		if p.Mark&NOSCHED != 0 {
			if q1 != p {
				sched(ctxt, q1, q)
			}
			for ; p != nil; p = p.Link {
				if p.Mark&NOSCHED == 0 {
					break
				}
				q = p
			}
			p1 = p
			q1 = p
			o = 0
			continue
		}
		if p.Mark&(LABEL|SYNC) != 0 {
			if q1 != p {
				sched(ctxt, q1, q)
			}
			q1 = p
			o = 1
		}
		if p.Mark&(BRANCH|SYNC) != 0 {
			sched(ctxt, q1, p)
			q1 = p1
			o = 0
		}
		if o >= NSCHED {
			sched(ctxt, q1, p)
			q1 = p1
			o = 0
		}
		q = p
	}
}
Пример #13
0
/*
// instruction scheduling
	if(debug['Q'] == 0)
		return;

	curtext = nil;
	q = nil;	// p - 1
	q1 = firstp;	// top of block
	o = 0;		// count of instructions
	for(p = firstp; p != nil; p = p1) {
		p1 = p->link;
		o++;
		if(p->mark & NOSCHED){
			if(q1 != p){
				sched(q1, q);
			}
			for(; p != nil; p = p->link){
				if(!(p->mark & NOSCHED))
					break;
				q = p;
			}
			p1 = p;
			q1 = p;
			o = 0;
			continue;
		}
		if(p->mark & (LABEL|SYNC)) {
			if(q1 != p)
				sched(q1, q);
			q1 = p;
			o = 1;
		}
		if(p->mark & (BRANCH|SYNC)) {
			sched(q1, p);
			q1 = p1;
			o = 0;
		}
		if(o >= NSCHED) {
			sched(q1, p);
			q1 = p1;
			o = 0;
		}
		q = p;
	}
*/
func stacksplit(ctxt *obj.Link, p *obj.Prog, framesize int32) *obj.Prog {
	// MOVD	g_stackguard(g), R3
	p = obj.Appendp(ctxt, p)

	p.As = AMOVD
	p.From.Type = obj.TYPE_MEM
	p.From.Reg = REGG
	p.From.Offset = 2 * int64(ctxt.Arch.Ptrsize) // G.stackguard0
	if ctxt.Cursym.Cfunc != 0 {
		p.From.Offset = 3 * int64(ctxt.Arch.Ptrsize) // G.stackguard1
	}
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R3

	var q *obj.Prog
	if framesize <= obj.StackSmall {
		// small stack: SP < stackguard
		//	CMP	stackguard, SP
		p = obj.Appendp(ctxt, p)

		p.As = ACMPU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R3
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REGSP
	} else if framesize <= obj.StackBig {
		// large stack: SP-framesize < stackguard-StackSmall
		//	ADD $-framesize, SP, R4
		//	CMP stackguard, R4
		p = obj.Appendp(ctxt, p)

		p.As = AADD
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(-framesize)
		p.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R4

		p = obj.Appendp(ctxt, p)
		p.As = ACMPU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R3
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R4
	} else {
		// Such a large stack we need to protect against wraparound.
		// If SP is close to zero:
		//	SP-stackguard+StackGuard <= framesize + (StackGuard-StackSmall)
		// The +StackGuard on both sides is required to keep the left side positive:
		// SP is allowed to be slightly below stackguard. See stack.h.
		//
		// Preemption sets stackguard to StackPreempt, a very large value.
		// That breaks the math above, so we have to check for that explicitly.
		//	// stackguard is R3
		//	CMP	R3, $StackPreempt
		//	BEQ	label-of-call-to-morestack
		//	ADD	$StackGuard, SP, R4
		//	SUB	R3, R4
		//	MOVD	$(framesize+(StackGuard-StackSmall)), R31
		//	CMPU	R31, R4
		p = obj.Appendp(ctxt, p)

		p.As = ACMP
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R3
		p.To.Type = obj.TYPE_CONST
		p.To.Offset = obj.StackPreempt

		p = obj.Appendp(ctxt, p)
		q = p
		p.As = ABEQ
		p.To.Type = obj.TYPE_BRANCH

		p = obj.Appendp(ctxt, p)
		p.As = AADD
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = obj.StackGuard
		p.Reg = REGSP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R4

		p = obj.Appendp(ctxt, p)
		p.As = ASUB
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R3
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R4

		p = obj.Appendp(ctxt, p)
		p.As = AMOVD
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(framesize) + obj.StackGuard - obj.StackSmall
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REGTMP

		p = obj.Appendp(ctxt, p)
		p.As = ACMPU
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REGTMP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R4
	}

	// q1: BLT	done
	p = obj.Appendp(ctxt, p)
	q1 := p

	p.As = ABLT
	p.To.Type = obj.TYPE_BRANCH

	// MOVD	LR, R5
	p = obj.Appendp(ctxt, p)

	p.As = AMOVD
	p.From.Type = obj.TYPE_REG
	p.From.Reg = REG_LR
	p.To.Type = obj.TYPE_REG
	p.To.Reg = REG_R5
	if q != nil {
		q.Pcond = p
	}

	var morestacksym *obj.LSym
	if ctxt.Cursym.Cfunc != 0 {
		morestacksym = obj.Linklookup(ctxt, "runtime.morestackc", 0)
	} else if ctxt.Cursym.Text.From3.Offset&obj.NEEDCTXT == 0 {
		morestacksym = obj.Linklookup(ctxt, "runtime.morestack_noctxt", 0)
	} else {
		morestacksym = obj.Linklookup(ctxt, "runtime.morestack", 0)
	}

	if ctxt.Flag_dynlink {
		// Avoid calling morestack via a PLT when dynamically linking.  The
		// PLT stubs generated by the system linker on ppc64le when "std r2,
		// 24(r1)" to save the TOC pointer in their callers stack
		// frame. Unfortunately (and necessarily) morestack is called before
		// the function that calls it sets up its frame and so the PLT ends
		// up smashing the saved TOC pointer for its caller's caller.
		//
		// According to the ABI documentation there is a mechanism to avoid
		// the TOC save that the PLT stub does (put a R_PPC64_TOCSAVE
		// relocation on the nop after the call to morestack) but at the time
		// of writing it is not supported at all by gold and my attempt to
		// use it with ld.bfd caused an internal linker error. So this hack
		// seems preferable.

		// MOVD $runtime.morestack(SB), R12
		p = obj.Appendp(ctxt, p)
		p.As = AMOVD
		p.From.Type = obj.TYPE_MEM
		p.From.Sym = morestacksym
		p.From.Name = obj.NAME_GOTREF
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_R12

		// MOVD R12, CTR
		p = obj.Appendp(ctxt, p)
		p.As = AMOVD
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R12
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_CTR

		// BL CTR
		p = obj.Appendp(ctxt, p)
		p.As = obj.ACALL
		p.From.Type = obj.TYPE_REG
		p.From.Reg = REG_R12
		p.To.Type = obj.TYPE_REG
		p.To.Reg = REG_CTR
	} else {
		// BL	runtime.morestack(SB)
		p = obj.Appendp(ctxt, p)

		p.As = ABL
		p.To.Type = obj.TYPE_BRANCH
		p.To.Sym = morestacksym
	}
	// BR	start
	p = obj.Appendp(ctxt, p)

	p.As = ABR
	p.To.Type = obj.TYPE_BRANCH
	p.Pcond = ctxt.Cursym.Text.Link

	// placeholder for q1's jump target
	p = obj.Appendp(ctxt, p)

	p.As = obj.ANOP // zero-width place holder
	q1.Pcond = p

	return p
}
Пример #14
0
func preprocess(ctxt *obj.Link, cursym *obj.LSym) {
	// TODO(minux): add morestack short-cuts with small fixed frame-size.
	ctxt.Cursym = cursym

	if cursym.Text == nil || cursym.Text.Link == nil {
		return
	}

	p := cursym.Text
	textstksiz := p.To.Offset
	if textstksiz == -8 {
		// Compatibility hack.
		p.From3.Offset |= obj.NOFRAME
		textstksiz = 0
	}
	if textstksiz%8 != 0 {
		ctxt.Diag("frame size %d not a multiple of 8", textstksiz)
	}
	if p.From3.Offset&obj.NOFRAME != 0 {
		if textstksiz != 0 {
			ctxt.Diag("NOFRAME functions must have a frame size of 0, not %d", textstksiz)
		}
	}

	cursym.Args = p.To.Val.(int32)
	cursym.Locals = int32(textstksiz)

	/*
	 * find leaf subroutines
	 * strip NOPs
	 * expand RET
	 * expand BECOME pseudo
	 */
	if ctxt.Debugvlog != 0 {
		fmt.Fprintf(ctxt.Bso, "%5.2f noops\n", obj.Cputime())
	}
	ctxt.Bso.Flush()

	var q *obj.Prog
	var q1 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		switch p.As {
		/* too hard, just leave alone */
		case obj.ATEXT:
			q = p

			p.Mark |= LABEL | LEAF | SYNC
			if p.Link != nil {
				p.Link.Mark |= LABEL
			}

		case ANOR:
			q = p
			if p.To.Type == obj.TYPE_REG {
				if p.To.Reg == REGZERO {
					p.Mark |= LABEL | SYNC
				}
			}

		case ALWAR,
			ASTWCCC,
			AECIWX,
			AECOWX,
			AEIEIO,
			AICBI,
			AISYNC,
			ATLBIE,
			ATLBIEL,
			ASLBIA,
			ASLBIE,
			ASLBMFEE,
			ASLBMFEV,
			ASLBMTE,
			ADCBF,
			ADCBI,
			ADCBST,
			ADCBT,
			ADCBTST,
			ADCBZ,
			ASYNC,
			ATLBSYNC,
			APTESYNC,
			ATW,
			AWORD,
			ARFI,
			ARFCI,
			ARFID,
			AHRFID:
			q = p
			p.Mark |= LABEL | SYNC
			continue

		case AMOVW, AMOVWZ, AMOVD:
			q = p
			if p.From.Reg >= REG_SPECIAL || p.To.Reg >= REG_SPECIAL {
				p.Mark |= LABEL | SYNC
			}
			continue

		case AFABS,
			AFABSCC,
			AFADD,
			AFADDCC,
			AFCTIW,
			AFCTIWCC,
			AFCTIWZ,
			AFCTIWZCC,
			AFDIV,
			AFDIVCC,
			AFMADD,
			AFMADDCC,
			AFMOVD,
			AFMOVDU,
			/* case AFMOVDS: */
			AFMOVS,
			AFMOVSU,

			/* case AFMOVSD: */
			AFMSUB,
			AFMSUBCC,
			AFMUL,
			AFMULCC,
			AFNABS,
			AFNABSCC,
			AFNEG,
			AFNEGCC,
			AFNMADD,
			AFNMADDCC,
			AFNMSUB,
			AFNMSUBCC,
			AFRSP,
			AFRSPCC,
			AFSUB,
			AFSUBCC:
			q = p

			p.Mark |= FLOAT
			continue

		case ABL,
			ABCL,
			obj.ADUFFZERO,
			obj.ADUFFCOPY:
			cursym.Text.Mark &^= LEAF
			fallthrough

		case ABC,
			ABEQ,
			ABGE,
			ABGT,
			ABLE,
			ABLT,
			ABNE,
			ABR,
			ABVC,
			ABVS:
			p.Mark |= BRANCH
			q = p
			q1 = p.Pcond
			if q1 != nil {
				for q1.As == obj.ANOP {
					q1 = q1.Link
					p.Pcond = q1
				}

				if q1.Mark&LEAF == 0 {
					q1.Mark |= LABEL
				}
			} else {
				p.Mark |= LABEL
			}
			q1 = p.Link
			if q1 != nil {
				q1.Mark |= LABEL
			}
			continue

		case AFCMPO, AFCMPU:
			q = p
			p.Mark |= FCMP | FLOAT
			continue

		case obj.ARET:
			q = p
			if p.Link != nil {
				p.Link.Mark |= LABEL
			}
			continue

		case obj.ANOP:
			q1 = p.Link
			q.Link = q1 /* q is non-nop */
			q1.Mark |= p.Mark
			continue

		default:
			q = p
			continue
		}
	}

	autosize := int32(0)
	var aoffset int
	var mov int
	var o int
	var p1 *obj.Prog
	var p2 *obj.Prog
	for p := cursym.Text; p != nil; p = p.Link {
		o = int(p.As)
		switch o {
		case obj.ATEXT:
			mov = AMOVD
			aoffset = 0
			autosize = int32(textstksiz)

			if p.Mark&LEAF != 0 && autosize == 0 && p.From3.Offset&obj.NOFRAME == 0 {
				// A leaf function with no locals has no frame.
				p.From3.Offset |= obj.NOFRAME
			}

			if p.From3.Offset&obj.NOFRAME == 0 {
				// If there is a stack frame at all, it includes
				// space to save the LR.
				autosize += int32(ctxt.FixedFrameSize())
			}

			p.To.Offset = int64(autosize)

			q = p

			if ctxt.Flag_shared != 0 && cursym.Name != "runtime.duffzero" && cursym.Name != "runtime.duffcopy" && cursym.Name != "runtime.stackBarrier" {
				// When compiling Go into PIC, all functions must start
				// with instructions to load the TOC pointer into r2:
				//
				//	addis r2, r12, .TOC.-func@ha
				//	addi r2, r2, .TOC.-func@l+4
				//
				// We could probably skip this prologue in some situations
				// but it's a bit subtle. However, it is both safe and
				// necessary to leave the prologue off duffzero and
				// duffcopy as we rely on being able to jump to a specific
				// instruction offset for them, and stackBarrier is only
				// ever called from an overwritten LR-save slot on the
				// stack (when r12 will not be remotely the right thing)
				// but fortunately does not access global data.
				//
				// These are AWORDS because there is no (afaict) way to
				// generate the addis instruction except as part of the
				// load of a large constant, and in that case there is no
				// way to use r12 as the source.
				q = obj.Appendp(ctxt, q)
				q.As = AWORD
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = 0x3c4c0000
				q = obj.Appendp(ctxt, q)
				q.As = AWORD
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = 0x38420000
				rel := obj.Addrel(ctxt.Cursym)
				rel.Off = 0
				rel.Siz = 8
				rel.Sym = obj.Linklookup(ctxt, ".TOC.", 0)
				rel.Type = obj.R_ADDRPOWER_PCREL
			}

			if cursym.Text.From3.Offset&obj.NOSPLIT == 0 {
				q = stacksplit(ctxt, q, autosize) // emit split check
			}

			if autosize != 0 {
				/* use MOVDU to adjust R1 when saving R31, if autosize is small */
				if cursym.Text.Mark&LEAF == 0 && autosize >= -BIG && autosize <= BIG {
					mov = AMOVDU
					aoffset = int(-autosize)
				} else {
					q = obj.Appendp(ctxt, q)
					q.As = AADD
					q.Lineno = p.Lineno
					q.From.Type = obj.TYPE_CONST
					q.From.Offset = int64(-autosize)
					q.To.Type = obj.TYPE_REG
					q.To.Reg = REGSP
					q.Spadj = +autosize
				}
			} else if cursym.Text.Mark&LEAF == 0 {
				// A very few functions that do not return to their caller
				// (e.g. gogo) are not identified as leaves but still have
				// no frame.
				cursym.Text.Mark |= LEAF
			}

			if cursym.Text.Mark&LEAF != 0 {
				cursym.Leaf = 1
				break
			}

			q = obj.Appendp(ctxt, q)
			q.As = AMOVD
			q.Lineno = p.Lineno
			q.From.Type = obj.TYPE_REG
			q.From.Reg = REG_LR
			q.To.Type = obj.TYPE_REG
			q.To.Reg = REGTMP

			q = obj.Appendp(ctxt, q)
			q.As = int16(mov)
			q.Lineno = p.Lineno
			q.From.Type = obj.TYPE_REG
			q.From.Reg = REGTMP
			q.To.Type = obj.TYPE_MEM
			q.To.Offset = int64(aoffset)
			q.To.Reg = REGSP
			if q.As == AMOVDU {
				q.Spadj = int32(-aoffset)
			}

			if ctxt.Flag_shared != 0 {
				q = obj.Appendp(ctxt, q)
				q.As = AMOVD
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R2
				q.To.Type = obj.TYPE_MEM
				q.To.Reg = REGSP
				q.To.Offset = 24
			}

			if cursym.Text.From3.Offset&obj.WRAPPER != 0 {
				// if(g->panic != nil && g->panic->argp == FP) g->panic->argp = bottom-of-frame
				//
				//	MOVD g_panic(g), R3
				//	CMP R0, R3
				//	BEQ end
				//	MOVD panic_argp(R3), R4
				//	ADD $(autosize+8), R1, R5
				//	CMP R4, R5
				//	BNE end
				//	ADD $8, R1, R6
				//	MOVD R6, panic_argp(R3)
				// end:
				//	NOP
				//
				// The NOP is needed to give the jumps somewhere to land.
				// It is a liblink NOP, not a ppc64 NOP: it encodes to 0 instruction bytes.

				q = obj.Appendp(ctxt, q)

				q.As = AMOVD
				q.From.Type = obj.TYPE_MEM
				q.From.Reg = REGG
				q.From.Offset = 4 * int64(ctxt.Arch.Ptrsize) // G.panic
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R3

				q = obj.Appendp(ctxt, q)
				q.As = ACMP
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R0
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R3

				q = obj.Appendp(ctxt, q)
				q.As = ABEQ
				q.To.Type = obj.TYPE_BRANCH
				p1 = q

				q = obj.Appendp(ctxt, q)
				q.As = AMOVD
				q.From.Type = obj.TYPE_MEM
				q.From.Reg = REG_R3
				q.From.Offset = 0 // Panic.argp
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R4

				q = obj.Appendp(ctxt, q)
				q.As = AADD
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(autosize) + ctxt.FixedFrameSize()
				q.Reg = REGSP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R5

				q = obj.Appendp(ctxt, q)
				q.As = ACMP
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R4
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R5

				q = obj.Appendp(ctxt, q)
				q.As = ABNE
				q.To.Type = obj.TYPE_BRANCH
				p2 = q

				q = obj.Appendp(ctxt, q)
				q.As = AADD
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = ctxt.FixedFrameSize()
				q.Reg = REGSP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_R6

				q = obj.Appendp(ctxt, q)
				q.As = AMOVD
				q.From.Type = obj.TYPE_REG
				q.From.Reg = REG_R6
				q.To.Type = obj.TYPE_MEM
				q.To.Reg = REG_R3
				q.To.Offset = 0 // Panic.argp

				q = obj.Appendp(ctxt, q)

				q.As = obj.ANOP
				p1.Pcond = q
				p2.Pcond = q
			}

		case obj.ARET:
			if p.From.Type == obj.TYPE_CONST {
				ctxt.Diag("using BECOME (%v) is not supported!", p)
				break
			}

			retTarget := p.To.Sym

			if cursym.Text.Mark&LEAF != 0 {
				if autosize == 0 {
					p.As = ABR
					p.From = obj.Addr{}
					if retTarget == nil {
						p.To.Type = obj.TYPE_REG
						p.To.Reg = REG_LR
					} else {
						p.To.Type = obj.TYPE_BRANCH
						p.To.Sym = retTarget
					}
					p.Mark |= BRANCH
					break
				}

				p.As = AADD
				p.From.Type = obj.TYPE_CONST
				p.From.Offset = int64(autosize)
				p.To.Type = obj.TYPE_REG
				p.To.Reg = REGSP
				p.Spadj = -autosize

				q = ctxt.NewProg()
				q.As = ABR
				q.Lineno = p.Lineno
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REG_LR
				q.Mark |= BRANCH
				q.Spadj = +autosize

				q.Link = p.Link
				p.Link = q
				break
			}

			p.As = AMOVD
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = 0
			p.From.Reg = REGSP
			p.To.Type = obj.TYPE_REG
			p.To.Reg = REGTMP

			q = ctxt.NewProg()
			q.As = AMOVD
			q.Lineno = p.Lineno
			q.From.Type = obj.TYPE_REG
			q.From.Reg = REGTMP
			q.To.Type = obj.TYPE_REG
			q.To.Reg = REG_LR

			q.Link = p.Link
			p.Link = q
			p = q

			if false {
				// Debug bad returns
				q = ctxt.NewProg()

				q.As = AMOVD
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_MEM
				q.From.Offset = 0
				q.From.Reg = REGTMP
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REGTMP

				q.Link = p.Link
				p.Link = q
				p = q
			}

			if autosize != 0 {
				q = ctxt.NewProg()
				q.As = AADD
				q.Lineno = p.Lineno
				q.From.Type = obj.TYPE_CONST
				q.From.Offset = int64(autosize)
				q.To.Type = obj.TYPE_REG
				q.To.Reg = REGSP
				q.Spadj = -autosize

				q.Link = p.Link
				p.Link = q
			}

			q1 = ctxt.NewProg()
			q1.As = ABR
			q1.Lineno = p.Lineno
			if retTarget == nil {
				q1.To.Type = obj.TYPE_REG
				q1.To.Reg = REG_LR
			} else {
				q1.To.Type = obj.TYPE_BRANCH
				q1.To.Sym = retTarget
			}
			q1.Mark |= BRANCH
			q1.Spadj = +autosize

			q1.Link = q.Link
			q.Link = q1
		case AADD:
			if p.To.Type == obj.TYPE_REG && p.To.Reg == REGSP && p.From.Type == obj.TYPE_CONST {
				p.Spadj = int32(-p.From.Offset)
			}
		}
	}
}