示例#1
0
文件: ggen.go 项目: glycerine/zygomys
// Called after regopt and peep have run.
// Expand CHECKNIL pseudo-op into actual nil pointer check.
func expandchecks(firstp *obj.Prog) {
	var p1 *obj.Prog
	var p2 *obj.Prog

	for p := firstp; p != nil; p = p.Link {
		if p.As != obj.ACHECKNIL {
			continue
		}
		if gc.Debug_checknil != 0 && p.Lineno > 1 { // p->lineno==1 in generated wrappers
			gc.Warnl(p.Lineno, "generated nil check")
		}

		// check is
		//	CMP arg, $0
		//	JNE 2(PC) (likely)
		//	MOV AX, 0
		p1 = gc.Ctxt.NewProg()

		p2 = gc.Ctxt.NewProg()
		gc.Clearp(p1)
		gc.Clearp(p2)
		p1.Link = p2
		p2.Link = p.Link
		p.Link = p1
		p1.Lineno = p.Lineno
		p2.Lineno = p.Lineno
		p1.Pc = 9999
		p2.Pc = 9999
		p.As = cmpptr
		p.To.Type = obj.TYPE_CONST
		p.To.Offset = 0
		p1.As = x86.AJNE
		p1.From.Type = obj.TYPE_CONST
		p1.From.Offset = 1 // likely
		p1.To.Type = obj.TYPE_BRANCH
		p1.To.Val = p2.Link

		// crash by write to memory address 0.
		// if possible, since we know arg is 0, use 0(arg),
		// which will be shorter to encode than plain 0.
		p2.As = x86.AMOVL

		p2.From.Type = obj.TYPE_REG
		p2.From.Reg = x86.REG_AX
		if regtyp(&p.From) {
			p2.To.Type = obj.TYPE_MEM
			p2.To.Reg = p.From.Reg
		} else {
			p2.To.Type = obj.TYPE_MEM
			p2.To.Reg = x86.REG_NONE
		}

		p2.To.Offset = 0
	}
}
示例#2
0
文件: ggen.go 项目: glycerine/zygomys
// Called after regopt and peep have run.
// Expand CHECKNIL pseudo-op into actual nil pointer check.
func expandchecks(firstp *obj.Prog) {
	for p := firstp; p != nil; p = p.Link {
		if gc.Debug_checknil != 0 && gc.Ctxt.Debugvlog != 0 {
			fmt.Printf("expandchecks: %v\n", p)
		}
		if p.As != obj.ACHECKNIL {
			continue
		}
		if gc.Debug_checknil != 0 && p.Lineno > 1 { // p->lineno==1 in generated wrappers
			gc.Warnl(p.Lineno, "generated nil check")
		}
		if p.From.Type != obj.TYPE_REG {
			gc.Fatalf("invalid nil check %v\n", p)
		}

		// check is
		//	CMPBNE arg, $0, 2(PC) [likely]
		//	MOVD   R0, 0(R0)
		p1 := gc.Ctxt.NewProg()

		gc.Clearp(p1)
		p1.Link = p.Link
		p.Link = p1
		p1.Lineno = p.Lineno
		p1.Pc = 9999
		p.As = s390x.ACMPBNE
		p.From3 = new(obj.Addr)
		p.From3.Type = obj.TYPE_CONST
		p.From3.Offset = 0

		p.To.Type = obj.TYPE_BRANCH
		p.To.Val = p1.Link

		// crash by write to memory address 0.
		p1.As = s390x.AMOVD

		p1.From.Type = obj.TYPE_REG
		p1.From.Reg = s390x.REGZERO
		p1.To.Type = obj.TYPE_MEM
		p1.To.Reg = s390x.REGZERO
		p1.To.Offset = 0
	}
}
示例#3
0
文件: ggen.go 项目: glycerine/zygomys
// Called after regopt and peep have run.
// Expand CHECKNIL pseudo-op into actual nil pointer check.
func expandchecks(firstp *obj.Prog) {
	var p1 *obj.Prog

	for p := firstp; p != nil; p = p.Link {
		if gc.Debug_checknil != 0 && gc.Ctxt.Debugvlog != 0 {
			fmt.Printf("expandchecks: %v\n", p)
		}
		if p.As != obj.ACHECKNIL {
			continue
		}
		if gc.Debug_checknil != 0 && p.Lineno > 1 { // p->lineno==1 in generated wrappers
			gc.Warnl(p.Lineno, "generated nil check")
		}
		if p.From.Type != obj.TYPE_REG {
			gc.Fatalf("invalid nil check %v\n", p)
		}

		// check is
		//	CBNZ arg, 2(PC)
		//	MOVD ZR, 0(arg)
		p1 = gc.Ctxt.NewProg()
		gc.Clearp(p1)
		p1.Link = p.Link
		p.Link = p1
		p1.Lineno = p.Lineno
		p1.Pc = 9999

		p.As = arm64.ACBNZ
		p.To.Type = obj.TYPE_BRANCH
		p.To.Val = p1.Link

		// crash by write to memory address 0.
		p1.As = arm64.AMOVD
		p1.From.Type = obj.TYPE_REG
		p1.From.Reg = arm64.REGZERO
		p1.To.Type = obj.TYPE_MEM
		p1.To.Reg = p.From.Reg
		p1.To.Offset = 0
	}
}
示例#4
0
文件: ggen.go 项目: glycerine/zygomys
// Called after regopt and peep have run.
// Expand CHECKNIL pseudo-op into actual nil pointer check.
func expandchecks(firstp *obj.Prog) {
	var reg int
	var p1 *obj.Prog

	for p := firstp; p != nil; p = p.Link {
		if p.As != obj.ACHECKNIL {
			continue
		}
		if gc.Debug_checknil != 0 && p.Lineno > 1 { // p->lineno==1 in generated wrappers
			gc.Warnl(p.Lineno, "generated nil check")
		}
		if p.From.Type != obj.TYPE_REG {
			gc.Fatalf("invalid nil check %v", p)
		}
		reg = int(p.From.Reg)

		// check is
		//	CMP arg, $0
		//	MOV.EQ arg, 0(arg)
		p1 = gc.Ctxt.NewProg()

		gc.Clearp(p1)
		p1.Link = p.Link
		p.Link = p1
		p1.Lineno = p.Lineno
		p1.Pc = 9999
		p1.As = arm.AMOVW
		p1.From.Type = obj.TYPE_REG
		p1.From.Reg = int16(reg)
		p1.To.Type = obj.TYPE_MEM
		p1.To.Reg = int16(reg)
		p1.To.Offset = 0
		p1.Scond = arm.C_SCOND_EQ
		p.As = arm.ACMP
		p.From.Type = obj.TYPE_CONST
		p.From.Reg = 0
		p.From.Offset = 0
		p.Reg = int16(reg)
	}
}
示例#5
0
文件: ssa.go 项目: glycerine/zygomys
func ssaGenValue(s *gc.SSAGenState, v *ssa.Value) {
	s.SetLineno(v.Line)
	switch v.Op {
	case ssa.OpAMD64ADDQ, ssa.OpAMD64ADDL:
		r := gc.SSARegNum(v)
		r1 := gc.SSARegNum(v.Args[0])
		r2 := gc.SSARegNum(v.Args[1])
		switch {
		case r == r1:
			p := gc.Prog(v.Op.Asm())
			p.From.Type = obj.TYPE_REG
			p.From.Reg = r2
			p.To.Type = obj.TYPE_REG
			p.To.Reg = r
		case r == r2:
			p := gc.Prog(v.Op.Asm())
			p.From.Type = obj.TYPE_REG
			p.From.Reg = r1
			p.To.Type = obj.TYPE_REG
			p.To.Reg = r
		default:
			var asm obj.As
			if v.Op == ssa.OpAMD64ADDQ {
				asm = x86.ALEAQ
			} else {
				asm = x86.ALEAL
			}
			p := gc.Prog(asm)
			p.From.Type = obj.TYPE_MEM
			p.From.Reg = r1
			p.From.Scale = 1
			p.From.Index = r2
			p.To.Type = obj.TYPE_REG
			p.To.Reg = r
		}
	// 2-address opcode arithmetic
	case ssa.OpAMD64SUBQ, ssa.OpAMD64SUBL,
		ssa.OpAMD64MULQ, ssa.OpAMD64MULL,
		ssa.OpAMD64ANDQ, ssa.OpAMD64ANDL,
		ssa.OpAMD64ORQ, ssa.OpAMD64ORL,
		ssa.OpAMD64XORQ, ssa.OpAMD64XORL,
		ssa.OpAMD64SHLQ, ssa.OpAMD64SHLL,
		ssa.OpAMD64SHRQ, ssa.OpAMD64SHRL, ssa.OpAMD64SHRW, ssa.OpAMD64SHRB,
		ssa.OpAMD64SARQ, ssa.OpAMD64SARL, ssa.OpAMD64SARW, ssa.OpAMD64SARB,
		ssa.OpAMD64ADDSS, ssa.OpAMD64ADDSD, ssa.OpAMD64SUBSS, ssa.OpAMD64SUBSD,
		ssa.OpAMD64MULSS, ssa.OpAMD64MULSD, ssa.OpAMD64DIVSS, ssa.OpAMD64DIVSD,
		ssa.OpAMD64PXOR:
		r := gc.SSARegNum(v)
		if r != gc.SSARegNum(v.Args[0]) {
			v.Fatalf("input[0] and output not in same register %s", v.LongString())
		}
		opregreg(v.Op.Asm(), r, gc.SSARegNum(v.Args[1]))

	case ssa.OpAMD64DIVQ, ssa.OpAMD64DIVL, ssa.OpAMD64DIVW,
		ssa.OpAMD64DIVQU, ssa.OpAMD64DIVLU, ssa.OpAMD64DIVWU,
		ssa.OpAMD64MODQ, ssa.OpAMD64MODL, ssa.OpAMD64MODW,
		ssa.OpAMD64MODQU, ssa.OpAMD64MODLU, ssa.OpAMD64MODWU:

		// Arg[0] is already in AX as it's the only register we allow
		// and AX is the only output
		x := gc.SSARegNum(v.Args[1])

		// CPU faults upon signed overflow, which occurs when most
		// negative int is divided by -1.
		var j *obj.Prog
		if v.Op == ssa.OpAMD64DIVQ || v.Op == ssa.OpAMD64DIVL ||
			v.Op == ssa.OpAMD64DIVW || v.Op == ssa.OpAMD64MODQ ||
			v.Op == ssa.OpAMD64MODL || v.Op == ssa.OpAMD64MODW {

			var c *obj.Prog
			switch v.Op {
			case ssa.OpAMD64DIVQ, ssa.OpAMD64MODQ:
				c = gc.Prog(x86.ACMPQ)
				j = gc.Prog(x86.AJEQ)
				// go ahead and sign extend to save doing it later
				gc.Prog(x86.ACQO)

			case ssa.OpAMD64DIVL, ssa.OpAMD64MODL:
				c = gc.Prog(x86.ACMPL)
				j = gc.Prog(x86.AJEQ)
				gc.Prog(x86.ACDQ)

			case ssa.OpAMD64DIVW, ssa.OpAMD64MODW:
				c = gc.Prog(x86.ACMPW)
				j = gc.Prog(x86.AJEQ)
				gc.Prog(x86.ACWD)
			}
			c.From.Type = obj.TYPE_REG
			c.From.Reg = x
			c.To.Type = obj.TYPE_CONST
			c.To.Offset = -1

			j.To.Type = obj.TYPE_BRANCH

		}

		// for unsigned ints, we sign extend by setting DX = 0
		// signed ints were sign extended above
		if v.Op == ssa.OpAMD64DIVQU || v.Op == ssa.OpAMD64MODQU ||
			v.Op == ssa.OpAMD64DIVLU || v.Op == ssa.OpAMD64MODLU ||
			v.Op == ssa.OpAMD64DIVWU || v.Op == ssa.OpAMD64MODWU {
			c := gc.Prog(x86.AXORQ)
			c.From.Type = obj.TYPE_REG
			c.From.Reg = x86.REG_DX
			c.To.Type = obj.TYPE_REG
			c.To.Reg = x86.REG_DX
		}

		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = x

		// signed division, rest of the check for -1 case
		if j != nil {
			j2 := gc.Prog(obj.AJMP)
			j2.To.Type = obj.TYPE_BRANCH

			var n *obj.Prog
			if v.Op == ssa.OpAMD64DIVQ || v.Op == ssa.OpAMD64DIVL ||
				v.Op == ssa.OpAMD64DIVW {
				// n * -1 = -n
				n = gc.Prog(x86.ANEGQ)
				n.To.Type = obj.TYPE_REG
				n.To.Reg = x86.REG_AX
			} else {
				// n % -1 == 0
				n = gc.Prog(x86.AXORQ)
				n.From.Type = obj.TYPE_REG
				n.From.Reg = x86.REG_DX
				n.To.Type = obj.TYPE_REG
				n.To.Reg = x86.REG_DX
			}

			j.To.Val = n
			j2.To.Val = s.Pc()
		}

	case ssa.OpAMD64HMULQ, ssa.OpAMD64HMULL, ssa.OpAMD64HMULW, ssa.OpAMD64HMULB,
		ssa.OpAMD64HMULQU, ssa.OpAMD64HMULLU, ssa.OpAMD64HMULWU, ssa.OpAMD64HMULBU:
		// the frontend rewrites constant division by 8/16/32 bit integers into
		// HMUL by a constant
		// SSA rewrites generate the 64 bit versions

		// Arg[0] is already in AX as it's the only register we allow
		// and DX is the only output we care about (the high bits)
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[1])

		// IMULB puts the high portion in AH instead of DL,
		// so move it to DL for consistency
		if v.Type.Size() == 1 {
			m := gc.Prog(x86.AMOVB)
			m.From.Type = obj.TYPE_REG
			m.From.Reg = x86.REG_AH
			m.To.Type = obj.TYPE_REG
			m.To.Reg = x86.REG_DX
		}

	case ssa.OpAMD64AVGQU:
		// compute (x+y)/2 unsigned.
		// Do a 64-bit add, the overflow goes into the carry.
		// Shift right once and pull the carry back into the 63rd bit.
		r := gc.SSARegNum(v)
		if r != gc.SSARegNum(v.Args[0]) {
			v.Fatalf("input[0] and output not in same register %s", v.LongString())
		}
		p := gc.Prog(x86.AADDQ)
		p.From.Type = obj.TYPE_REG
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r
		p.From.Reg = gc.SSARegNum(v.Args[1])
		p = gc.Prog(x86.ARCRQ)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 1
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r

	case ssa.OpAMD64ADDQconst, ssa.OpAMD64ADDLconst:
		r := gc.SSARegNum(v)
		a := gc.SSARegNum(v.Args[0])
		if r == a {
			if v.AuxInt == 1 {
				var asm obj.As
				// Software optimization manual recommends add $1,reg.
				// But inc/dec is 1 byte smaller. ICC always uses inc
				// Clang/GCC choose depending on flags, but prefer add.
				// Experiments show that inc/dec is both a little faster
				// and make a binary a little smaller.
				if v.Op == ssa.OpAMD64ADDQconst {
					asm = x86.AINCQ
				} else {
					asm = x86.AINCL
				}
				p := gc.Prog(asm)
				p.To.Type = obj.TYPE_REG
				p.To.Reg = r
				return
			}
			if v.AuxInt == -1 {
				var asm obj.As
				if v.Op == ssa.OpAMD64ADDQconst {
					asm = x86.ADECQ
				} else {
					asm = x86.ADECL
				}
				p := gc.Prog(asm)
				p.To.Type = obj.TYPE_REG
				p.To.Reg = r
				return
			}
			p := gc.Prog(v.Op.Asm())
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = v.AuxInt
			p.To.Type = obj.TYPE_REG
			p.To.Reg = r
			return
		}
		var asm obj.As
		if v.Op == ssa.OpAMD64ADDQconst {
			asm = x86.ALEAQ
		} else {
			asm = x86.ALEAL
		}
		p := gc.Prog(asm)
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = a
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r

	case ssa.OpAMD64CMOVQEQconst, ssa.OpAMD64CMOVLEQconst, ssa.OpAMD64CMOVWEQconst,
		ssa.OpAMD64CMOVQNEconst, ssa.OpAMD64CMOVLNEconst, ssa.OpAMD64CMOVWNEconst:
		r := gc.SSARegNum(v)
		if r != gc.SSARegNum(v.Args[0]) {
			v.Fatalf("input[0] and output not in same register %s", v.LongString())
		}

		// Constant into AX
		p := gc.Prog(moveByType(v.Type))
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = x86.REG_AX

		p = gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = x86.REG_AX
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r

	case ssa.OpAMD64MULQconst, ssa.OpAMD64MULLconst:
		r := gc.SSARegNum(v)
		if r != gc.SSARegNum(v.Args[0]) {
			v.Fatalf("input[0] and output not in same register %s", v.LongString())
		}
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r
		// TODO: Teach doasm to compile the three-address multiply imul $c, r1, r2
		// then we don't need to use resultInArg0 for these ops.
		//p.From3 = new(obj.Addr)
		//p.From3.Type = obj.TYPE_REG
		//p.From3.Reg = gc.SSARegNum(v.Args[0])

	case ssa.OpAMD64SUBQconst, ssa.OpAMD64SUBLconst,
		ssa.OpAMD64ANDQconst, ssa.OpAMD64ANDLconst,
		ssa.OpAMD64ORQconst, ssa.OpAMD64ORLconst,
		ssa.OpAMD64XORQconst, ssa.OpAMD64XORLconst,
		ssa.OpAMD64SHLQconst, ssa.OpAMD64SHLLconst,
		ssa.OpAMD64SHRQconst, ssa.OpAMD64SHRLconst, ssa.OpAMD64SHRWconst, ssa.OpAMD64SHRBconst,
		ssa.OpAMD64SARQconst, ssa.OpAMD64SARLconst, ssa.OpAMD64SARWconst, ssa.OpAMD64SARBconst,
		ssa.OpAMD64ROLQconst, ssa.OpAMD64ROLLconst, ssa.OpAMD64ROLWconst, ssa.OpAMD64ROLBconst:
		r := gc.SSARegNum(v)
		if r != gc.SSARegNum(v.Args[0]) {
			v.Fatalf("input[0] and output not in same register %s", v.LongString())
		}
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r
	case ssa.OpAMD64SBBQcarrymask, ssa.OpAMD64SBBLcarrymask:
		r := gc.SSARegNum(v)
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = r
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r
	case ssa.OpAMD64LEAQ1, ssa.OpAMD64LEAQ2, ssa.OpAMD64LEAQ4, ssa.OpAMD64LEAQ8:
		r := gc.SSARegNum(v.Args[0])
		i := gc.SSARegNum(v.Args[1])
		p := gc.Prog(x86.ALEAQ)
		switch v.Op {
		case ssa.OpAMD64LEAQ1:
			p.From.Scale = 1
			if i == x86.REG_SP {
				r, i = i, r
			}
		case ssa.OpAMD64LEAQ2:
			p.From.Scale = 2
		case ssa.OpAMD64LEAQ4:
			p.From.Scale = 4
		case ssa.OpAMD64LEAQ8:
			p.From.Scale = 8
		}
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = r
		p.From.Index = i
		gc.AddAux(&p.From, v)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64LEAQ:
		p := gc.Prog(x86.ALEAQ)
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.From, v)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64CMPQ, ssa.OpAMD64CMPL, ssa.OpAMD64CMPW, ssa.OpAMD64CMPB,
		ssa.OpAMD64TESTQ, ssa.OpAMD64TESTL, ssa.OpAMD64TESTW, ssa.OpAMD64TESTB:
		opregreg(v.Op.Asm(), gc.SSARegNum(v.Args[1]), gc.SSARegNum(v.Args[0]))
	case ssa.OpAMD64UCOMISS, ssa.OpAMD64UCOMISD:
		// Go assembler has swapped operands for UCOMISx relative to CMP,
		// must account for that right here.
		opregreg(v.Op.Asm(), gc.SSARegNum(v.Args[0]), gc.SSARegNum(v.Args[1]))
	case ssa.OpAMD64CMPQconst, ssa.OpAMD64CMPLconst, ssa.OpAMD64CMPWconst, ssa.OpAMD64CMPBconst:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[0])
		p.To.Type = obj.TYPE_CONST
		p.To.Offset = v.AuxInt
	case ssa.OpAMD64TESTQconst, ssa.OpAMD64TESTLconst, ssa.OpAMD64TESTWconst, ssa.OpAMD64TESTBconst:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v.Args[0])
	case ssa.OpAMD64MOVLconst, ssa.OpAMD64MOVQconst:
		x := gc.SSARegNum(v)
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = v.AuxInt
		p.To.Type = obj.TYPE_REG
		p.To.Reg = x
		// If flags are live at this instruction, suppress the
		// MOV $0,AX -> XOR AX,AX optimization.
		if v.Aux != nil {
			p.Mark |= x86.PRESERVEFLAGS
		}
	case ssa.OpAMD64MOVSSconst, ssa.OpAMD64MOVSDconst:
		x := gc.SSARegNum(v)
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_FCONST
		p.From.Val = math.Float64frombits(uint64(v.AuxInt))
		p.To.Type = obj.TYPE_REG
		p.To.Reg = x
	case ssa.OpAMD64MOVQload, ssa.OpAMD64MOVSSload, ssa.OpAMD64MOVSDload, ssa.OpAMD64MOVLload, ssa.OpAMD64MOVWload, ssa.OpAMD64MOVBload, ssa.OpAMD64MOVBQSXload, ssa.OpAMD64MOVWQSXload, ssa.OpAMD64MOVLQSXload, ssa.OpAMD64MOVOload:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.From, v)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64MOVQloadidx8, ssa.OpAMD64MOVSDloadidx8:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.From, v)
		p.From.Scale = 8
		p.From.Index = gc.SSARegNum(v.Args[1])
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64MOVLloadidx4, ssa.OpAMD64MOVSSloadidx4:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.From, v)
		p.From.Scale = 4
		p.From.Index = gc.SSARegNum(v.Args[1])
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64MOVWloadidx2:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.From, v)
		p.From.Scale = 2
		p.From.Index = gc.SSARegNum(v.Args[1])
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64MOVBloadidx1, ssa.OpAMD64MOVWloadidx1, ssa.OpAMD64MOVLloadidx1, ssa.OpAMD64MOVQloadidx1, ssa.OpAMD64MOVSSloadidx1, ssa.OpAMD64MOVSDloadidx1:
		r := gc.SSARegNum(v.Args[0])
		i := gc.SSARegNum(v.Args[1])
		if i == x86.REG_SP {
			r, i = i, r
		}
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_MEM
		p.From.Reg = r
		p.From.Scale = 1
		p.From.Index = i
		gc.AddAux(&p.From, v)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpAMD64MOVQstore, ssa.OpAMD64MOVSSstore, ssa.OpAMD64MOVSDstore, ssa.OpAMD64MOVLstore, ssa.OpAMD64MOVWstore, ssa.OpAMD64MOVBstore, ssa.OpAMD64MOVOstore:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[1])
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.To, v)
	case ssa.OpAMD64MOVQstoreidx8, ssa.OpAMD64MOVSDstoreidx8:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[2])
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		p.To.Scale = 8
		p.To.Index = gc.SSARegNum(v.Args[1])
		gc.AddAux(&p.To, v)
	case ssa.OpAMD64MOVSSstoreidx4, ssa.OpAMD64MOVLstoreidx4:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[2])
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		p.To.Scale = 4
		p.To.Index = gc.SSARegNum(v.Args[1])
		gc.AddAux(&p.To, v)
	case ssa.OpAMD64MOVWstoreidx2:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[2])
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		p.To.Scale = 2
		p.To.Index = gc.SSARegNum(v.Args[1])
		gc.AddAux(&p.To, v)
	case ssa.OpAMD64MOVBstoreidx1, ssa.OpAMD64MOVWstoreidx1, ssa.OpAMD64MOVLstoreidx1, ssa.OpAMD64MOVQstoreidx1, ssa.OpAMD64MOVSSstoreidx1, ssa.OpAMD64MOVSDstoreidx1:
		r := gc.SSARegNum(v.Args[0])
		i := gc.SSARegNum(v.Args[1])
		if i == x86.REG_SP {
			r, i = i, r
		}
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[2])
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = r
		p.To.Scale = 1
		p.To.Index = i
		gc.AddAux(&p.To, v)
	case ssa.OpAMD64MOVQstoreconst, ssa.OpAMD64MOVLstoreconst, ssa.OpAMD64MOVWstoreconst, ssa.OpAMD64MOVBstoreconst:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		sc := v.AuxValAndOff()
		p.From.Offset = sc.Val()
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux2(&p.To, v, sc.Off())
	case ssa.OpAMD64MOVQstoreconstidx1, ssa.OpAMD64MOVQstoreconstidx8, ssa.OpAMD64MOVLstoreconstidx1, ssa.OpAMD64MOVLstoreconstidx4, ssa.OpAMD64MOVWstoreconstidx1, ssa.OpAMD64MOVWstoreconstidx2, ssa.OpAMD64MOVBstoreconstidx1:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_CONST
		sc := v.AuxValAndOff()
		p.From.Offset = sc.Val()
		r := gc.SSARegNum(v.Args[0])
		i := gc.SSARegNum(v.Args[1])
		switch v.Op {
		case ssa.OpAMD64MOVBstoreconstidx1, ssa.OpAMD64MOVWstoreconstidx1, ssa.OpAMD64MOVLstoreconstidx1, ssa.OpAMD64MOVQstoreconstidx1:
			p.To.Scale = 1
			if i == x86.REG_SP {
				r, i = i, r
			}
		case ssa.OpAMD64MOVWstoreconstidx2:
			p.To.Scale = 2
		case ssa.OpAMD64MOVLstoreconstidx4:
			p.To.Scale = 4
		case ssa.OpAMD64MOVQstoreconstidx8:
			p.To.Scale = 8
		}
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = r
		p.To.Index = i
		gc.AddAux2(&p.To, v, sc.Off())
	case ssa.OpAMD64MOVLQSX, ssa.OpAMD64MOVWQSX, ssa.OpAMD64MOVBQSX, ssa.OpAMD64MOVLQZX, ssa.OpAMD64MOVWQZX, ssa.OpAMD64MOVBQZX,
		ssa.OpAMD64CVTSL2SS, ssa.OpAMD64CVTSL2SD, ssa.OpAMD64CVTSQ2SS, ssa.OpAMD64CVTSQ2SD,
		ssa.OpAMD64CVTTSS2SL, ssa.OpAMD64CVTTSD2SL, ssa.OpAMD64CVTTSS2SQ, ssa.OpAMD64CVTTSD2SQ,
		ssa.OpAMD64CVTSS2SD, ssa.OpAMD64CVTSD2SS:
		opregreg(v.Op.Asm(), gc.SSARegNum(v), gc.SSARegNum(v.Args[0]))
	case ssa.OpAMD64DUFFZERO:
		off := duffStart(v.AuxInt)
		adj := duffAdj(v.AuxInt)
		var p *obj.Prog
		if adj != 0 {
			p = gc.Prog(x86.AADDQ)
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = adj
			p.To.Type = obj.TYPE_REG
			p.To.Reg = x86.REG_DI
		}
		p = gc.Prog(obj.ADUFFZERO)
		p.To.Type = obj.TYPE_ADDR
		p.To.Sym = gc.Linksym(gc.Pkglookup("duffzero", gc.Runtimepkg))
		p.To.Offset = off
	case ssa.OpAMD64MOVOconst:
		if v.AuxInt != 0 {
			v.Unimplementedf("MOVOconst can only do constant=0")
		}
		r := gc.SSARegNum(v)
		opregreg(x86.AXORPS, r, r)
	case ssa.OpAMD64DUFFCOPY:
		p := gc.Prog(obj.ADUFFCOPY)
		p.To.Type = obj.TYPE_ADDR
		p.To.Sym = gc.Linksym(gc.Pkglookup("duffcopy", gc.Runtimepkg))
		p.To.Offset = v.AuxInt

	case ssa.OpCopy, ssa.OpAMD64MOVQconvert: // TODO: use MOVQreg for reg->reg copies instead of OpCopy?
		if v.Type.IsMemory() {
			return
		}
		x := gc.SSARegNum(v.Args[0])
		y := gc.SSARegNum(v)
		if x != y {
			opregreg(moveByType(v.Type), y, x)
		}
	case ssa.OpLoadReg:
		if v.Type.IsFlags() {
			v.Unimplementedf("load flags not implemented: %v", v.LongString())
			return
		}
		p := gc.Prog(loadByType(v.Type))
		n, off := gc.AutoVar(v.Args[0])
		p.From.Type = obj.TYPE_MEM
		p.From.Node = n
		p.From.Sym = gc.Linksym(n.Sym)
		p.From.Offset = off
		if n.Class == gc.PPARAM || n.Class == gc.PPARAMOUT {
			p.From.Name = obj.NAME_PARAM
			p.From.Offset += n.Xoffset
		} else {
			p.From.Name = obj.NAME_AUTO
		}
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)

	case ssa.OpStoreReg:
		if v.Type.IsFlags() {
			v.Unimplementedf("store flags not implemented: %v", v.LongString())
			return
		}
		p := gc.Prog(storeByType(v.Type))
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[0])
		n, off := gc.AutoVar(v)
		p.To.Type = obj.TYPE_MEM
		p.To.Node = n
		p.To.Sym = gc.Linksym(n.Sym)
		p.To.Offset = off
		if n.Class == gc.PPARAM || n.Class == gc.PPARAMOUT {
			p.To.Name = obj.NAME_PARAM
			p.To.Offset += n.Xoffset
		} else {
			p.To.Name = obj.NAME_AUTO
		}
	case ssa.OpPhi:
		// just check to make sure regalloc and stackalloc did it right
		if v.Type.IsMemory() {
			return
		}
		f := v.Block.Func
		loc := f.RegAlloc[v.ID]
		for _, a := range v.Args {
			if aloc := f.RegAlloc[a.ID]; aloc != loc { // TODO: .Equal() instead?
				v.Fatalf("phi arg at different location than phi: %v @ %v, but arg %v @ %v\n%s\n", v, loc, a, aloc, v.Block.Func)
			}
		}
	case ssa.OpInitMem:
		// memory arg needs no code
	case ssa.OpArg:
		// input args need no code
	case ssa.OpAMD64LoweredGetClosurePtr:
		// Output is hardwired to DX only,
		// and DX contains the closure pointer on
		// closure entry, and this "instruction"
		// is scheduled to the very beginning
		// of the entry block.
	case ssa.OpAMD64LoweredGetG:
		r := gc.SSARegNum(v)
		// See the comments in cmd/avail/obj/x86/obj6.go
		// near CanUse1InsnTLS for a detailed explanation of these instructions.
		if x86.CanUse1InsnTLS(gc.Ctxt) {
			// MOVQ (TLS), r
			p := gc.Prog(x86.AMOVQ)
			p.From.Type = obj.TYPE_MEM
			p.From.Reg = x86.REG_TLS
			p.To.Type = obj.TYPE_REG
			p.To.Reg = r
		} else {
			// MOVQ TLS, r
			// MOVQ (r)(TLS*1), r
			p := gc.Prog(x86.AMOVQ)
			p.From.Type = obj.TYPE_REG
			p.From.Reg = x86.REG_TLS
			p.To.Type = obj.TYPE_REG
			p.To.Reg = r
			q := gc.Prog(x86.AMOVQ)
			q.From.Type = obj.TYPE_MEM
			q.From.Reg = r
			q.From.Index = x86.REG_TLS
			q.From.Scale = 1
			q.To.Type = obj.TYPE_REG
			q.To.Reg = r
		}
	case ssa.OpAMD64CALLstatic:
		if v.Aux.(*gc.Sym) == gc.Deferreturn.Sym {
			// Deferred calls will appear to be returning to
			// the CALL deferreturn(SB) that we are about to emit.
			// However, the stack trace code will show the line
			// of the instruction byte before the return PC.
			// To avoid that being an unrelated instruction,
			// insert an actual hardware NOP that will have the right line number.
			// This is different from obj.ANOP, which is a virtual no-op
			// that doesn't make it into the instruction stream.
			ginsnop()
		}
		p := gc.Prog(obj.ACALL)
		p.To.Type = obj.TYPE_MEM
		p.To.Name = obj.NAME_EXTERN
		p.To.Sym = gc.Linksym(v.Aux.(*gc.Sym))
		if gc.Maxarg < v.AuxInt {
			gc.Maxarg = v.AuxInt
		}
	case ssa.OpAMD64CALLclosure:
		p := gc.Prog(obj.ACALL)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v.Args[0])
		if gc.Maxarg < v.AuxInt {
			gc.Maxarg = v.AuxInt
		}
	case ssa.OpAMD64CALLdefer:
		p := gc.Prog(obj.ACALL)
		p.To.Type = obj.TYPE_MEM
		p.To.Name = obj.NAME_EXTERN
		p.To.Sym = gc.Linksym(gc.Deferproc.Sym)
		if gc.Maxarg < v.AuxInt {
			gc.Maxarg = v.AuxInt
		}
	case ssa.OpAMD64CALLgo:
		p := gc.Prog(obj.ACALL)
		p.To.Type = obj.TYPE_MEM
		p.To.Name = obj.NAME_EXTERN
		p.To.Sym = gc.Linksym(gc.Newproc.Sym)
		if gc.Maxarg < v.AuxInt {
			gc.Maxarg = v.AuxInt
		}
	case ssa.OpAMD64CALLinter:
		p := gc.Prog(obj.ACALL)
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v.Args[0])
		if gc.Maxarg < v.AuxInt {
			gc.Maxarg = v.AuxInt
		}
	case ssa.OpAMD64NEGQ, ssa.OpAMD64NEGL,
		ssa.OpAMD64BSWAPQ, ssa.OpAMD64BSWAPL,
		ssa.OpAMD64NOTQ, ssa.OpAMD64NOTL:
		r := gc.SSARegNum(v)
		if r != gc.SSARegNum(v.Args[0]) {
			v.Fatalf("input[0] and output not in same register %s", v.LongString())
		}
		p := gc.Prog(v.Op.Asm())
		p.To.Type = obj.TYPE_REG
		p.To.Reg = r
	case ssa.OpAMD64BSFQ, ssa.OpAMD64BSFL, ssa.OpAMD64BSFW,
		ssa.OpAMD64BSRQ, ssa.OpAMD64BSRL, ssa.OpAMD64BSRW,
		ssa.OpAMD64SQRTSD:
		p := gc.Prog(v.Op.Asm())
		p.From.Type = obj.TYPE_REG
		p.From.Reg = gc.SSARegNum(v.Args[0])
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
	case ssa.OpSP, ssa.OpSB:
		// nothing to do
	case ssa.OpAMD64SETEQ, ssa.OpAMD64SETNE,
		ssa.OpAMD64SETL, ssa.OpAMD64SETLE,
		ssa.OpAMD64SETG, ssa.OpAMD64SETGE,
		ssa.OpAMD64SETGF, ssa.OpAMD64SETGEF,
		ssa.OpAMD64SETB, ssa.OpAMD64SETBE,
		ssa.OpAMD64SETORD, ssa.OpAMD64SETNAN,
		ssa.OpAMD64SETA, ssa.OpAMD64SETAE:
		p := gc.Prog(v.Op.Asm())
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)

	case ssa.OpAMD64SETNEF:
		p := gc.Prog(v.Op.Asm())
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
		q := gc.Prog(x86.ASETPS)
		q.To.Type = obj.TYPE_REG
		q.To.Reg = x86.REG_AX
		// ORL avoids partial register write and is smaller than ORQ, used by old compiler
		opregreg(x86.AORL, gc.SSARegNum(v), x86.REG_AX)

	case ssa.OpAMD64SETEQF:
		p := gc.Prog(v.Op.Asm())
		p.To.Type = obj.TYPE_REG
		p.To.Reg = gc.SSARegNum(v)
		q := gc.Prog(x86.ASETPC)
		q.To.Type = obj.TYPE_REG
		q.To.Reg = x86.REG_AX
		// ANDL avoids partial register write and is smaller than ANDQ, used by old compiler
		opregreg(x86.AANDL, gc.SSARegNum(v), x86.REG_AX)

	case ssa.OpAMD64InvertFlags:
		v.Fatalf("InvertFlags should never make it to codegen %v", v.LongString())
	case ssa.OpAMD64FlagEQ, ssa.OpAMD64FlagLT_ULT, ssa.OpAMD64FlagLT_UGT, ssa.OpAMD64FlagGT_ULT, ssa.OpAMD64FlagGT_UGT:
		v.Fatalf("Flag* ops should never make it to codegen %v", v.LongString())
	case ssa.OpAMD64REPSTOSQ:
		gc.Prog(x86.AREP)
		gc.Prog(x86.ASTOSQ)
	case ssa.OpAMD64REPMOVSQ:
		gc.Prog(x86.AREP)
		gc.Prog(x86.AMOVSQ)
	case ssa.OpVarDef:
		gc.Gvardef(v.Aux.(*gc.Node))
	case ssa.OpVarKill:
		gc.Gvarkill(v.Aux.(*gc.Node))
	case ssa.OpVarLive:
		gc.Gvarlive(v.Aux.(*gc.Node))
	case ssa.OpKeepAlive:
		if !v.Args[0].Type.IsPtrShaped() {
			v.Fatalf("keeping non-pointer alive %v", v.Args[0])
		}
		n, off := gc.AutoVar(v.Args[0])
		if n == nil {
			v.Fatalf("KeepLive with non-spilled value %s %s", v, v.Args[0])
		}
		if off != 0 {
			v.Fatalf("KeepLive with non-zero offset spill location %s:%d", n, off)
		}
		gc.Gvarlive(n)
	case ssa.OpAMD64LoweredNilCheck:
		// Optimization - if the subsequent block has a load or store
		// at the same address, we don't need to issue this instruction.
		mem := v.Args[1]
		for _, w := range v.Block.Succs[0].Block().Values {
			if w.Op == ssa.OpPhi {
				if w.Type.IsMemory() {
					mem = w
				}
				continue
			}
			if len(w.Args) == 0 || !w.Args[len(w.Args)-1].Type.IsMemory() {
				// w doesn't use a store - can't be a memory op.
				continue
			}
			if w.Args[len(w.Args)-1] != mem {
				v.Fatalf("wrong store after nilcheck v=%s w=%s", v, w)
			}
			switch w.Op {
			case ssa.OpAMD64MOVQload, ssa.OpAMD64MOVLload, ssa.OpAMD64MOVWload, ssa.OpAMD64MOVBload,
				ssa.OpAMD64MOVQstore, ssa.OpAMD64MOVLstore, ssa.OpAMD64MOVWstore, ssa.OpAMD64MOVBstore,
				ssa.OpAMD64MOVBQSXload, ssa.OpAMD64MOVWQSXload, ssa.OpAMD64MOVLQSXload,
				ssa.OpAMD64MOVSSload, ssa.OpAMD64MOVSDload, ssa.OpAMD64MOVOload,
				ssa.OpAMD64MOVSSstore, ssa.OpAMD64MOVSDstore, ssa.OpAMD64MOVOstore:
				if w.Args[0] == v.Args[0] && w.Aux == nil && w.AuxInt >= 0 && w.AuxInt < minZeroPage {
					if gc.Debug_checknil != 0 && int(v.Line) > 1 {
						gc.Warnl(v.Line, "removed nil check")
					}
					return
				}
			case ssa.OpAMD64MOVQstoreconst, ssa.OpAMD64MOVLstoreconst, ssa.OpAMD64MOVWstoreconst, ssa.OpAMD64MOVBstoreconst:
				off := ssa.ValAndOff(v.AuxInt).Off()
				if w.Args[0] == v.Args[0] && w.Aux == nil && off >= 0 && off < minZeroPage {
					if gc.Debug_checknil != 0 && int(v.Line) > 1 {
						gc.Warnl(v.Line, "removed nil check")
					}
					return
				}
			}
			if w.Type.IsMemory() {
				if w.Op == ssa.OpVarDef || w.Op == ssa.OpVarKill || w.Op == ssa.OpVarLive {
					// these ops are OK
					mem = w
					continue
				}
				// We can't delay the nil check past the next store.
				break
			}
		}
		// Issue a load which will fault if the input is nil.
		// TODO: We currently use the 2-byte instruction TESTB AX, (reg).
		// Should we use the 3-byte TESTB $0, (reg) instead?  It is larger
		// but it doesn't have false dependency on AX.
		// Or maybe allocate an output register and use MOVL (reg),reg2 ?
		// That trades clobbering flags for clobbering a register.
		p := gc.Prog(x86.ATESTB)
		p.From.Type = obj.TYPE_REG
		p.From.Reg = x86.REG_AX
		p.To.Type = obj.TYPE_MEM
		p.To.Reg = gc.SSARegNum(v.Args[0])
		gc.AddAux(&p.To, v)
		if gc.Debug_checknil != 0 && v.Line > 1 { // v.Line==1 in generated wrappers
			gc.Warnl(v.Line, "generated nil check")
		}
	default:
		v.Unimplementedf("genValue not implemented: %s", v.LongString())
	}
}
示例#6
0
文件: ggen.go 项目: glycerine/zygomys
// Called after regopt and peep have run.
// Expand CHECKNIL pseudo-op into actual nil pointer check.
func expandchecks(firstp *obj.Prog) {
	var p1 *obj.Prog
	var p2 *obj.Prog

	for p := firstp; p != nil; p = p.Link {
		if gc.Debug_checknil != 0 && gc.Ctxt.Debugvlog != 0 {
			fmt.Printf("expandchecks: %v\n", p)
		}
		if p.As != obj.ACHECKNIL {
			continue
		}
		if gc.Debug_checknil != 0 && p.Lineno > 1 { // p->lineno==1 in generated wrappers
			gc.Warnl(p.Lineno, "generated nil check")
		}
		if p.From.Type != obj.TYPE_REG {
			gc.Fatalf("invalid nil check %v\n", p)
		}

		/*
			// check is
			//	TD $4, R0, arg (R0 is always zero)
			// eqv. to:
			// 	tdeq r0, arg
			// NOTE: this needs special runtime support to make SIGTRAP recoverable.
			reg = p->from.reg;
			p->as = ATD;
			p->from = p->to = p->from3 = zprog.from;
			p->from.type = TYPE_CONST;
			p->from.offset = 4;
			p->from.reg = 0;
			p->reg = REGZERO;
			p->to.type = TYPE_REG;
			p->to.reg = reg;
		*/
		// check is
		//	CMP arg, R0
		//	BNE 2(PC) [likely]
		//	MOVD R0, 0(R0)
		p1 = gc.Ctxt.NewProg()

		p2 = gc.Ctxt.NewProg()
		gc.Clearp(p1)
		gc.Clearp(p2)
		p1.Link = p2
		p2.Link = p.Link
		p.Link = p1
		p1.Lineno = p.Lineno
		p2.Lineno = p.Lineno
		p1.Pc = 9999
		p2.Pc = 9999
		p.As = ppc64.ACMP
		p.To.Type = obj.TYPE_REG
		p.To.Reg = ppc64.REGZERO
		p1.As = ppc64.ABNE

		//p1->from.type = TYPE_CONST;
		//p1->from.offset = 1; // likely
		p1.To.Type = obj.TYPE_BRANCH

		p1.To.Val = p2.Link

		// crash by write to memory address 0.
		p2.As = ppc64.AMOVD

		p2.From.Type = obj.TYPE_REG
		p2.From.Reg = ppc64.REGZERO
		p2.To.Type = obj.TYPE_MEM
		p2.To.Reg = ppc64.REGZERO
		p2.To.Offset = 0
	}
}