Ejemplo n.º 1
0
Archivo: ggen.go Proyecto: Ericean/go
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		fmt.Printf("clearfat %v (%v, size: %d)\n", nl, nl.Type, nl.Type.Width)
	}

	w := uint64(uint64(nl.Type.Width))

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	c := uint64(w % 8) // bytes
	q := uint64(w / 8) // dwords

	if gc.Reginuse(ppc64.REGRT1) {
		gc.Fatal("%v in use during clearfat", obj.Rconv(ppc64.REGRT1))
	}

	var r0 gc.Node
	gc.Nodreg(&r0, gc.Types[gc.TUINT64], ppc64.REGZERO)
	var dst gc.Node
	gc.Nodreg(&dst, gc.Types[gc.Tptr], ppc64.REGRT1)
	gc.Regrealloc(&dst)
	gc.Agen(nl, &dst)

	var boff uint64
	if q > 128 {
		p := gins(ppc64.ASUB, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8

		var end gc.Node
		gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
		p = gins(ppc64.AMOVD, &dst, &end)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = int64(q * 8)

		p = gins(ppc64.AMOVDU, &r0, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = 8
		pl := (*obj.Prog)(p)

		p = gins(ppc64.ACMP, &dst, &end)
		gc.Patch(gc.Gbranch(ppc64.ABNE, nil, 0), pl)

		gc.Regfree(&end)

		// The loop leaves R3 on the last zeroed dword
		boff = 8
	} else if q >= 4 {
		p := gins(ppc64.ASUB, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8
		f := (*gc.Node)(gc.Sysfunc("duffzero"))
		p = gins(obj.ADUFFZERO, nil, f)
		gc.Afunclit(&p.To, f)

		// 4 and 128 = magic constants: see ../../runtime/asm_ppc64x.s
		p.To.Offset = int64(4 * (128 - q))

		// duffzero leaves R3 on the last zeroed dword
		boff = 8
	} else {
		var p *obj.Prog
		for t := uint64(0); t < q; t++ {
			p = gins(ppc64.AMOVD, &r0, &dst)
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = int64(8 * t)
		}

		boff = 8 * q
	}

	var p *obj.Prog
	for t := uint64(0); t < c; t++ {
		p = gins(ppc64.AMOVB, &r0, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = int64(t + boff)
	}

	gc.Regfree(&dst)
}
Ejemplo n.º 2
0
Archivo: cgen.go Proyecto: 4ad/go
func blockcopy(n, res *gc.Node, osrc, odst, w int64) {
	// determine alignment.
	// want to avoid unaligned access, so have to use
	// smaller operations for less aligned types.
	// for example moving [4]byte must use 4 MOVB not 1 MOVW.
	align := int(n.Type.Align)

	var op int
	switch align {
	default:
		gc.Fatalf("sgen: invalid alignment %d for %v", align, n.Type)

	case 1:
		op = mips.AMOVB

	case 2:
		op = mips.AMOVH

	case 4:
		op = mips.AMOVW

	case 8:
		op = mips.AMOVV
	}

	if w%int64(align) != 0 {
		gc.Fatalf("sgen: unaligned size %d (align=%d) for %v", w, align, n.Type)
	}
	c := int32(w / int64(align))

	// if we are copying forward on the stack and
	// the src and dst overlap, then reverse direction
	dir := align

	if osrc < odst && odst < osrc+w {
		dir = -dir
	}

	var dst gc.Node
	var src gc.Node
	if n.Ullman >= res.Ullman {
		gc.Agenr(n, &dst, res) // temporarily use dst
		gc.Regalloc(&src, gc.Types[gc.Tptr], nil)
		gins(mips.AMOVV, &dst, &src)
		if res.Op == gc.ONAME {
			gc.Gvardef(res)
		}
		gc.Agen(res, &dst)
	} else {
		if res.Op == gc.ONAME {
			gc.Gvardef(res)
		}
		gc.Agenr(res, &dst, res)
		gc.Agenr(n, &src, nil)
	}

	var tmp gc.Node
	gc.Regalloc(&tmp, gc.Types[gc.Tptr], nil)

	// set up end marker
	var nend gc.Node

	// move src and dest to the end of block if necessary
	if dir < 0 {
		if c >= 4 {
			gc.Regalloc(&nend, gc.Types[gc.Tptr], nil)
			gins(mips.AMOVV, &src, &nend)
		}

		p := gins(mips.AADDV, nil, &src)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = w

		p = gins(mips.AADDV, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = w
	} else {
		p := gins(mips.AADDV, nil, &src)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(-dir)

		p = gins(mips.AADDV, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(-dir)

		if c >= 4 {
			gc.Regalloc(&nend, gc.Types[gc.Tptr], nil)
			p := gins(mips.AMOVV, &src, &nend)
			p.From.Type = obj.TYPE_ADDR
			p.From.Offset = w
		}
	}

	// move
	// TODO: enable duffcopy for larger copies.
	if c >= 4 {
		p := gins(op, &src, &tmp)
		p.From.Type = obj.TYPE_MEM
		p.From.Offset = int64(dir)
		ploop := p

		p = gins(mips.AADDV, nil, &src)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(dir)

		p = gins(op, &tmp, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = int64(dir)

		p = gins(mips.AADDV, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = int64(dir)

		gc.Patch(ginsbranch(mips.ABNE, nil, &src, &nend, 0), ploop)
		gc.Regfree(&nend)
	} else {
		// TODO: Instead of generating ADDV $-8,R8; ADDV
		// $-8,R7; n*(MOVV 8(R8),R9; ADDV $8,R8; MOVV R9,8(R7);
		// ADDV $8,R7;) just generate the offsets directly and
		// eliminate the ADDs. That will produce shorter, more
		// pipeline-able code.
		var p *obj.Prog
		for ; c > 0; c-- {
			p = gins(op, &src, &tmp)
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = int64(dir)

			p = gins(mips.AADDV, nil, &src)
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = int64(dir)

			p = gins(op, &tmp, &dst)
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = int64(dir)

			p = gins(mips.AADDV, nil, &dst)
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = int64(dir)
		}
	}

	gc.Regfree(&dst)
	gc.Regfree(&src)
	gc.Regfree(&tmp)
}
Ejemplo n.º 3
0
func blockcopy(n, res *gc.Node, osrc, odst, w int64) {
	// determine alignment.
	// want to avoid unaligned access, so have to use
	// smaller operations for less aligned types.
	// for example moving [4]byte must use 4 MOVB not 1 MOVW.
	align := int(n.Type.Align)

	var op int
	switch align {
	default:
		gc.Fatalf("sgen: invalid alignment %d for %v", align, n.Type)

	case 1:
		op = arm.AMOVB

	case 2:
		op = arm.AMOVH

	case 4:
		op = arm.AMOVW
	}

	if w%int64(align) != 0 {
		gc.Fatalf("sgen: unaligned size %d (align=%d) for %v", w, align, n.Type)
	}
	c := int32(w / int64(align))

	if osrc%int64(align) != 0 || odst%int64(align) != 0 {
		gc.Fatalf("sgen: unaligned offset src %d or dst %d (align %d)", osrc, odst, align)
	}

	// if we are copying forward on the stack and
	// the src and dst overlap, then reverse direction
	dir := align
	if osrc < odst && int64(odst) < int64(osrc)+w {
		dir = -dir
	}

	if op == arm.AMOVW && !gc.Nacl && dir > 0 && c >= 4 && c <= 128 {
		var r0 gc.Node
		r0.Op = gc.OREGISTER
		r0.Reg = arm.REG_R0
		var r1 gc.Node
		r1.Op = gc.OREGISTER
		r1.Reg = arm.REG_R0 + 1
		var r2 gc.Node
		r2.Op = gc.OREGISTER
		r2.Reg = arm.REG_R0 + 2

		var src gc.Node
		gc.Regalloc(&src, gc.Types[gc.Tptr], &r1)
		var dst gc.Node
		gc.Regalloc(&dst, gc.Types[gc.Tptr], &r2)
		if n.Ullman >= res.Ullman {
			// eval n first
			gc.Agen(n, &src)

			if res.Op == gc.ONAME {
				gc.Gvardef(res)
			}
			gc.Agen(res, &dst)
		} else {
			// eval res first
			if res.Op == gc.ONAME {
				gc.Gvardef(res)
			}
			gc.Agen(res, &dst)
			gc.Agen(n, &src)
		}

		var tmp gc.Node
		gc.Regalloc(&tmp, gc.Types[gc.Tptr], &r0)
		f := gc.Sysfunc("duffcopy")
		p := gins(obj.ADUFFCOPY, nil, f)
		gc.Afunclit(&p.To, f)

		// 8 and 128 = magic constants: see ../../runtime/asm_arm.s
		p.To.Offset = 8 * (128 - int64(c))

		gc.Regfree(&tmp)
		gc.Regfree(&src)
		gc.Regfree(&dst)
		return
	}

	var dst gc.Node
	var src gc.Node
	if n.Ullman >= res.Ullman {
		gc.Agenr(n, &dst, res) // temporarily use dst
		gc.Regalloc(&src, gc.Types[gc.Tptr], nil)
		gins(arm.AMOVW, &dst, &src)
		if res.Op == gc.ONAME {
			gc.Gvardef(res)
		}
		gc.Agen(res, &dst)
	} else {
		if res.Op == gc.ONAME {
			gc.Gvardef(res)
		}
		gc.Agenr(res, &dst, res)
		gc.Agenr(n, &src, nil)
	}

	var tmp gc.Node
	gc.Regalloc(&tmp, gc.Types[gc.TUINT32], nil)

	// set up end marker
	var nend gc.Node

	if c >= 4 {
		gc.Regalloc(&nend, gc.Types[gc.TUINT32], nil)

		p := gins(arm.AMOVW, &src, &nend)
		p.From.Type = obj.TYPE_ADDR
		if dir < 0 {
			p.From.Offset = int64(dir)
		} else {
			p.From.Offset = w
		}
	}

	// move src and dest to the end of block if necessary
	if dir < 0 {
		p := gins(arm.AMOVW, &src, &src)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = w + int64(dir)

		p = gins(arm.AMOVW, &dst, &dst)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = w + int64(dir)
	}

	// move
	if c >= 4 {
		p := gins(op, &src, &tmp)
		p.From.Type = obj.TYPE_MEM
		p.From.Offset = int64(dir)
		p.Scond |= arm.C_PBIT
		ploop := p

		p = gins(op, &tmp, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = int64(dir)
		p.Scond |= arm.C_PBIT

		p = gins(arm.ACMP, &src, nil)
		raddr(&nend, p)

		gc.Patch(gc.Gbranch(arm.ABNE, nil, 0), ploop)
		gc.Regfree(&nend)
	} else {
		var p *obj.Prog
		for {
			tmp14 := c
			c--
			if tmp14 <= 0 {
				break
			}
			p = gins(op, &src, &tmp)
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = int64(dir)
			p.Scond |= arm.C_PBIT

			p = gins(op, &tmp, &dst)
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = int64(dir)
			p.Scond |= arm.C_PBIT
		}
	}

	gc.Regfree(&dst)
	gc.Regfree(&src)
	gc.Regfree(&tmp)
}
Ejemplo n.º 4
0
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		gc.Dump("\nclearfat", nl)
	}

	w := nl.Type.Width

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	c := w % 8 // bytes
	q := w / 8 // quads

	if q < 4 {
		// Write sequence of MOV 0, off(base) instead of using STOSQ.
		// The hope is that although the code will be slightly longer,
		// the MOVs will have no dependencies and pipeline better
		// than the unrolled STOSQ loop.
		// NOTE: Must use agen, not igen, so that optimizer sees address
		// being taken. We are not writing on field boundaries.
		var n1 gc.Node
		gc.Agenr(nl, &n1, nil)

		n1.Op = gc.OINDREG
		var z gc.Node
		gc.Nodconst(&z, gc.Types[gc.TUINT64], 0)
		for {
			tmp14 := q
			q--
			if tmp14 <= 0 {
				break
			}
			n1.Type = z.Type
			gins(x86.AMOVQ, &z, &n1)
			n1.Xoffset += 8
		}

		if c >= 4 {
			gc.Nodconst(&z, gc.Types[gc.TUINT32], 0)
			n1.Type = z.Type
			gins(x86.AMOVL, &z, &n1)
			n1.Xoffset += 4
			c -= 4
		}

		gc.Nodconst(&z, gc.Types[gc.TUINT8], 0)
		for {
			tmp15 := c
			c--
			if tmp15 <= 0 {
				break
			}
			n1.Type = z.Type
			gins(x86.AMOVB, &z, &n1)
			n1.Xoffset++
		}

		gc.Regfree(&n1)
		return
	}

	var oldn1 gc.Node
	var n1 gc.Node
	savex(x86.REG_DI, &n1, &oldn1, nil, gc.Types[gc.Tptr])
	gc.Agen(nl, &n1)

	var ax gc.Node
	var oldax gc.Node
	savex(x86.REG_AX, &ax, &oldax, nil, gc.Types[gc.Tptr])
	gconreg(x86.AMOVL, 0, x86.REG_AX)

	if q > 128 || gc.Nacl {
		gconreg(movptr, q, x86.REG_CX)
		gins(x86.AREP, nil, nil)   // repeat
		gins(x86.ASTOSQ, nil, nil) // STOQ AL,*(DI)+
	} else {
		if di := dzDI(q); di != 0 {
			gconreg(addptr, di, x86.REG_DI)
		}
		p := gins(obj.ADUFFZERO, nil, nil)
		p.To.Type = obj.TYPE_ADDR
		p.To.Sym = gc.Linksym(gc.Pkglookup("duffzero", gc.Runtimepkg))
		p.To.Offset = dzOff(q)
	}

	z := ax
	di := n1
	if w >= 8 && c >= 4 {
		di.Op = gc.OINDREG
		z.Type = gc.Types[gc.TINT64]
		di.Type = z.Type
		p := gins(x86.AMOVQ, &z, &di)
		p.To.Scale = 1
		p.To.Offset = c - 8
	} else if c >= 4 {
		di.Op = gc.OINDREG
		z.Type = gc.Types[gc.TINT32]
		di.Type = z.Type
		gins(x86.AMOVL, &z, &di)
		if c > 4 {
			p := gins(x86.AMOVL, &z, &di)
			p.To.Scale = 1
			p.To.Offset = c - 4
		}
	} else {
		for c > 0 {
			gins(x86.ASTOSB, nil, nil) // STOB AL,*(DI)+
			c--
		}
	}

	restx(&n1, &oldn1)
	restx(&ax, &oldax)
}
Ejemplo n.º 5
0
Archivo: ggen.go Proyecto: Greentor/go
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		fmt.Printf("clearfat %v (%v, size: %d)\n", nl, nl.Type, nl.Type.Width)
	}

	w := uint64(nl.Type.Width)

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	c := w % 8 // bytes
	q := w / 8 // dwords

	if gc.Reginuse(mips.REGRT1) {
		gc.Fatalf("%v in use during clearfat", obj.Rconv(mips.REGRT1))
	}

	var r0 gc.Node
	gc.Nodreg(&r0, gc.Types[gc.TUINT64], mips.REGZERO)
	var dst gc.Node
	gc.Nodreg(&dst, gc.Types[gc.Tptr], mips.REGRT1)
	gc.Regrealloc(&dst)
	gc.Agen(nl, &dst)

	var boff uint64
	if q > 128 {
		p := gins(mips.ASUBV, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8

		var end gc.Node
		gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
		p = gins(mips.AMOVV, &dst, &end)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = int64(q * 8)

		p = gins(mips.AMOVV, &r0, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = 8
		pl := p

		p = gins(mips.AADDV, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8

		gc.Patch(ginsbranch(mips.ABNE, nil, &dst, &end, 0), pl)

		gc.Regfree(&end)

		// The loop leaves R1 on the last zeroed dword
		boff = 8
		// TODO(dfc): https://golang.org/issue/12108
		// If DUFFZERO is used inside a tail call (see genwrapper) it will
		// overwrite the link register.
	} else if false && q >= 4 {
		p := gins(mips.ASUBV, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8
		f := gc.Sysfunc("duffzero")
		p = gins(obj.ADUFFZERO, nil, f)
		gc.Afunclit(&p.To, f)

		// 8 and 128 = magic constants: see ../../runtime/asm_mips64x.s
		p.To.Offset = int64(8 * (128 - q))

		// duffzero leaves R1 on the last zeroed dword
		boff = 8
	} else {
		var p *obj.Prog
		for t := uint64(0); t < q; t++ {
			p = gins(mips.AMOVV, &r0, &dst)
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = int64(8 * t)
		}

		boff = 8 * q
	}

	var p *obj.Prog
	for t := uint64(0); t < c; t++ {
		p = gins(mips.AMOVB, &r0, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = int64(t + boff)
	}

	gc.Regfree(&dst)
}
Ejemplo n.º 6
0
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		fmt.Printf("clearfat %v (%v, size: %d)\n", nl, nl.Type, nl.Type.Width)
	}

	w := uint64(uint64(nl.Type.Width))

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	c := uint64(w % 8) // bytes
	q := uint64(w / 8) // dwords

	var r0 gc.Node
	gc.Nodreg(&r0, gc.Types[gc.TUINT64], arm64.REGZERO)
	var dst gc.Node

	// REGRT1 is reserved on arm64, see arm64/gsubr.go.
	gc.Nodreg(&dst, gc.Types[gc.Tptr], arm64.REGRT1)
	gc.Agen(nl, &dst)

	var boff uint64
	if q > 128 {
		p := gins(arm64.ASUB, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8

		var end gc.Node
		gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
		p = gins(arm64.AMOVD, &dst, &end)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = int64(q * 8)

		p = gins(arm64.AMOVD, &r0, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = 8
		p.Scond = arm64.C_XPRE
		pl := (*obj.Prog)(p)

		p = gcmp(arm64.ACMP, &dst, &end)
		gc.Patch(gc.Gbranch(arm64.ABNE, nil, 0), pl)

		gc.Regfree(&end)

		// The loop leaves R16 on the last zeroed dword
		boff = 8
	} else if q >= 4 && !darwin { // darwin ld64 cannot handle BR26 reloc with non-zero addend
		p := gins(arm64.ASUB, nil, &dst)
		p.From.Type = obj.TYPE_CONST
		p.From.Offset = 8
		f := (*gc.Node)(gc.Sysfunc("duffzero"))
		p = gins(obj.ADUFFZERO, nil, f)
		gc.Afunclit(&p.To, f)

		// 4 and 128 = magic constants: see ../../runtime/asm_arm64x.s
		p.To.Offset = int64(4 * (128 - q))

		// duffzero leaves R16 on the last zeroed dword
		boff = 8
	} else {
		var p *obj.Prog
		for t := uint64(0); t < q; t++ {
			p = gins(arm64.AMOVD, &r0, &dst)
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = int64(8 * t)
		}

		boff = 8 * q
	}

	var p *obj.Prog
	for t := uint64(0); t < c; t++ {
		p = gins(arm64.AMOVB, &r0, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = int64(t + boff)
	}
}
Ejemplo n.º 7
0
Archivo: ggen.go Proyecto: arnold8/go
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		gc.Dump("\nclearfat", nl)
	}

	w := uint32(nl.Type.Width)

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	c := w % 4 // bytes
	q := w / 4 // quads

	var r0 gc.Node
	r0.Op = gc.OREGISTER

	r0.Reg = arm.REG_R0
	var r1 gc.Node
	r1.Op = gc.OREGISTER
	r1.Reg = arm.REG_R1
	var dst gc.Node
	gc.Regalloc(&dst, gc.Types[gc.Tptr], &r1)
	gc.Agen(nl, &dst)
	var nc gc.Node
	gc.Nodconst(&nc, gc.Types[gc.TUINT32], 0)
	var nz gc.Node
	gc.Regalloc(&nz, gc.Types[gc.TUINT32], &r0)
	gc.Cgen(&nc, &nz)

	if q > 128 {
		var end gc.Node
		gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
		p := gins(arm.AMOVW, &dst, &end)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = int64(q) * 4

		p = gins(arm.AMOVW, &nz, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = 4
		p.Scond |= arm.C_PBIT
		pl := p

		p = gins(arm.ACMP, &dst, nil)
		raddr(&end, p)
		gc.Patch(gc.Gbranch(arm.ABNE, nil, 0), pl)

		gc.Regfree(&end)
	} else if q >= 4 && !gc.Nacl {
		f := gc.Sysfunc("duffzero")
		p := gins(obj.ADUFFZERO, nil, f)
		gc.Afunclit(&p.To, f)

		// 4 and 128 = magic constants: see ../../runtime/asm_arm.s
		p.To.Offset = 4 * (128 - int64(q))
	} else {
		var p *obj.Prog
		for q > 0 {
			p = gins(arm.AMOVW, &nz, &dst)
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = 4
			p.Scond |= arm.C_PBIT

			//print("1. %v\n", p);
			q--
		}
	}

	var p *obj.Prog
	for c > 0 {
		p = gins(arm.AMOVB, &nz, &dst)
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = 1
		p.Scond |= arm.C_PBIT

		//print("2. %v\n", p);
		c--
	}

	gc.Regfree(&dst)
	gc.Regfree(&nz)
}
Ejemplo n.º 8
0
Archivo: ggen.go Proyecto: Samurais/go
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		gc.Dump("\nclearfat", nl)
	}

	w := uint32(nl.Type.Width)

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	c := w % 4 // bytes
	q := w / 4 // quads

	if q < 4 {
		// Write sequence of MOV 0, off(base) instead of using STOSL.
		// The hope is that although the code will be slightly longer,
		// the MOVs will have no dependencies and pipeline better
		// than the unrolled STOSL loop.
		// NOTE: Must use agen, not igen, so that optimizer sees address
		// being taken. We are not writing on field boundaries.
		var n1 gc.Node
		gc.Regalloc(&n1, gc.Types[gc.Tptr], nil)

		gc.Agen(nl, &n1)
		n1.Op = gc.OINDREG
		var z gc.Node
		gc.Nodconst(&z, gc.Types[gc.TUINT64], 0)
		for ; q > 0; q-- {
			n1.Type = z.Type
			gins(x86.AMOVL, &z, &n1)
			n1.Xoffset += 4
		}

		gc.Nodconst(&z, gc.Types[gc.TUINT8], 0)
		for ; c > 0; c-- {
			n1.Type = z.Type
			gins(x86.AMOVB, &z, &n1)
			n1.Xoffset++
		}

		gc.Regfree(&n1)
		return
	}

	var n1 gc.Node
	gc.Nodreg(&n1, gc.Types[gc.Tptr], x86.REG_DI)
	gc.Agen(nl, &n1)
	gconreg(x86.AMOVL, 0, x86.REG_AX)

	if q > 128 || (q >= 4 && gc.Nacl) {
		gconreg(x86.AMOVL, int64(q), x86.REG_CX)
		gins(x86.AREP, nil, nil)   // repeat
		gins(x86.ASTOSL, nil, nil) // STOL AL,*(DI)+
	} else if q >= 4 {
		p := gins(obj.ADUFFZERO, nil, nil)
		p.To.Type = obj.TYPE_ADDR
		p.To.Sym = gc.Linksym(gc.Pkglookup("duffzero", gc.Runtimepkg))

		// 1 and 128 = magic constants: see ../../runtime/asm_386.s
		p.To.Offset = 1 * (128 - int64(q))
	} else {
		for q > 0 {
			gins(x86.ASTOSL, nil, nil) // STOL AL,*(DI)+
			q--
		}
	}

	for c > 0 {
		gins(x86.ASTOSB, nil, nil) // STOB AL,*(DI)+
		c--
	}
}
Ejemplo n.º 9
0
Archivo: ggen.go Proyecto: 2thetop/go
// clearfat clears (i.e. replaces with zeros) the value pointed to by nl.
func clearfat(nl *gc.Node) {
	if gc.Debug['g'] != 0 {
		fmt.Printf("clearfat %v (%v, size: %d)\n", nl, nl.Type, nl.Type.Width)
	}

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	var dst gc.Node
	gc.Regalloc(&dst, gc.Types[gc.Tptr], nil)
	gc.Agen(nl, &dst)

	var boff int64
	w := nl.Type.Width
	if w > clearLoopCutoff {
		// Generate a loop clearing 256 bytes per iteration using XCs.
		var end gc.Node
		gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
		p := gins(s390x.AMOVD, &dst, &end)
		p.From.Type = obj.TYPE_ADDR
		p.From.Offset = w - (w % 256)

		p = gins(s390x.AXC, &dst, &dst)
		p.From.Type = obj.TYPE_MEM
		p.From.Offset = 0
		p.To.Type = obj.TYPE_MEM
		p.To.Offset = 0
		p.From3 = new(obj.Addr)
		p.From3.Offset = 256
		p.From3.Type = obj.TYPE_CONST
		pl := p

		ginscon(s390x.AADD, 256, &dst)
		gins(s390x.ACMP, &dst, &end)
		gc.Patch(gc.Gbranch(s390x.ABNE, nil, 0), pl)
		gc.Regfree(&end)
		w = w % 256
	}

	// Generate instructions to clear the remaining memory.
	for w > 0 {
		n := w

		// Can clear at most 256 bytes per instruction.
		if n > 256 {
			n = 256
		}

		switch n {
		// Handle very small clears using moves.
		case 8, 4, 2, 1:
			ins := s390x.AMOVB
			switch n {
			case 8:
				ins = s390x.AMOVD
			case 4:
				ins = s390x.AMOVW
			case 2:
				ins = s390x.AMOVH
			}
			p := gins(ins, nil, &dst)
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = 0
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = boff

		// Handle clears that would require multiple moves with a XC.
		default:
			p := gins(s390x.AXC, &dst, &dst)
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = boff
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = boff
			p.From3 = new(obj.Addr)
			p.From3.Offset = n
			p.From3.Type = obj.TYPE_CONST
		}

		boff += n
		w -= n
	}

	gc.Regfree(&dst)
}
Ejemplo n.º 10
0
/*
 * generate code to compute address of n,
 * a reference to a (perhaps nested) field inside
 * an array or struct.
 * return 0 on failure, 1 on success.
 * on success, leaves usable address in a.
 *
 * caller is responsible for calling sudoclean
 * after successful sudoaddable,
 * to release the register used for a.
 */
func sudoaddable(as int, n *gc.Node, a *obj.Addr) bool {
	if n.Type == nil {
		return false
	}

	*a = obj.Addr{}

	switch n.Op {
	case gc.OLITERAL:
		if !gc.Isconst(n, gc.CTINT) {
			break
		}
		v := n.Int()
		if v >= 32000 || v <= -32000 {
			break
		}
		switch as {
		default:
			return false

		case arm.AADD,
			arm.ASUB,
			arm.AAND,
			arm.AORR,
			arm.AEOR,
			arm.AMOVB,
			arm.AMOVBS,
			arm.AMOVBU,
			arm.AMOVH,
			arm.AMOVHS,
			arm.AMOVHU,
			arm.AMOVW:
			break
		}

		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		gc.Naddr(a, n)
		return true

	case gc.ODOT,
		gc.ODOTPTR:
		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		var nn *gc.Node
		var oary [10]int64
		o := gc.Dotoffset(n, oary[:], &nn)
		if nn == nil {
			sudoclean()
			return false
		}

		if nn.Addable && o == 1 && oary[0] >= 0 {
			// directly addressable set of DOTs
			n1 := *nn

			n1.Type = n.Type
			n1.Xoffset += oary[0]
			gc.Naddr(a, &n1)
			return true
		}

		gc.Regalloc(reg, gc.Types[gc.Tptr], nil)
		n1 := *reg
		n1.Op = gc.OINDREG
		if oary[0] >= 0 {
			gc.Agen(nn, reg)
			n1.Xoffset = oary[0]
		} else {
			gc.Cgen(nn, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[0] + 1)
		}

		for i := 1; i < o; i++ {
			if oary[i] >= 0 {
				gc.Fatal("can't happen")
			}
			gins(arm.AMOVW, &n1, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[i] + 1)
		}

		a.Type = obj.TYPE_NONE
		a.Name = obj.NAME_NONE
		n1.Type = n.Type
		gc.Naddr(a, &n1)
		return true

	case gc.OINDEX:
		return false
	}

	return false
}
Ejemplo n.º 11
0
func clearfat(nl *gc.Node) {
	/* clear a fat object */
	if gc.Debug['g'] != 0 {
		gc.Dump("\nclearfat", nl)
	}

	// Avoid taking the address for simple enough types.
	if gc.Componentgen(nil, nl) {
		return
	}

	w := nl.Type.Width

	if w > 1024 || (w >= 64 && (gc.Nacl || isPlan9)) {
		var oldn1 gc.Node
		var n1 gc.Node
		savex(x86.REG_DI, &n1, &oldn1, nil, gc.Types[gc.Tptr])
		gc.Agen(nl, &n1)

		var ax gc.Node
		var oldax gc.Node
		savex(x86.REG_AX, &ax, &oldax, nil, gc.Types[gc.Tptr])
		gconreg(x86.AMOVL, 0, x86.REG_AX)
		gconreg(movptr, w/8, x86.REG_CX)

		gins(x86.AREP, nil, nil)   // repeat
		gins(x86.ASTOSQ, nil, nil) // STOQ AL,*(DI)+

		if w%8 != 0 {
			n1.Op = gc.OINDREG
			clearfat_tail(&n1, w%8)
		}

		restx(&n1, &oldn1)
		restx(&ax, &oldax)
		return
	}

	if w >= 64 {
		var oldn1 gc.Node
		var n1 gc.Node
		savex(x86.REG_DI, &n1, &oldn1, nil, gc.Types[gc.Tptr])
		gc.Agen(nl, &n1)

		var vec_zero gc.Node
		var old_x0 gc.Node
		savex(x86.REG_X0, &vec_zero, &old_x0, nil, gc.Types[gc.TFLOAT64])
		gins(x86.AXORPS, &vec_zero, &vec_zero)

		if di := dzDI(w); di != 0 {
			gconreg(addptr, di, x86.REG_DI)
		}
		p := gins(obj.ADUFFZERO, nil, nil)
		p.To.Type = obj.TYPE_ADDR
		p.To.Sym = gc.Linksym(gc.Pkglookup("duffzero", gc.Runtimepkg))
		p.To.Offset = dzOff(w)

		if w%16 != 0 {
			n1.Op = gc.OINDREG
			n1.Xoffset -= 16 - w%16
			gins(x86.AMOVUPS, &vec_zero, &n1)
		}

		restx(&vec_zero, &old_x0)
		restx(&n1, &oldn1)
		return
	}

	// NOTE: Must use agen, not igen, so that optimizer sees address
	// being taken. We are not writing on field boundaries.
	var n1 gc.Node
	gc.Agenr(nl, &n1, nil)
	n1.Op = gc.OINDREG

	clearfat_tail(&n1, w)

	gc.Regfree(&n1)
}
Ejemplo n.º 12
0
/*
 * generate code to compute address of n,
 * a reference to a (perhaps nested) field inside
 * an array or struct.
 * return 0 on failure, 1 on success.
 * on success, leaves usable address in a.
 *
 * caller is responsible for calling sudoclean
 * after successful sudoaddable,
 * to release the register used for a.
 */
func sudoaddable(as int, n *gc.Node, a *obj.Addr) bool {
	if n.Type == nil {
		return false
	}

	*a = obj.Addr{}

	switch n.Op {
	case gc.OLITERAL:
		if !gc.Isconst(n, gc.CTINT) {
			break
		}
		v := n.Int()
		if v >= 32000 || v <= -32000 {
			break
		}
		switch as {
		default:
			return false

		case x86.AADDB,
			x86.AADDW,
			x86.AADDL,
			x86.AADDQ,
			x86.ASUBB,
			x86.ASUBW,
			x86.ASUBL,
			x86.ASUBQ,
			x86.AANDB,
			x86.AANDW,
			x86.AANDL,
			x86.AANDQ,
			x86.AORB,
			x86.AORW,
			x86.AORL,
			x86.AORQ,
			x86.AXORB,
			x86.AXORW,
			x86.AXORL,
			x86.AXORQ,
			x86.AINCB,
			x86.AINCW,
			x86.AINCL,
			x86.AINCQ,
			x86.ADECB,
			x86.ADECW,
			x86.ADECL,
			x86.ADECQ,
			x86.AMOVB,
			x86.AMOVW,
			x86.AMOVL,
			x86.AMOVQ:
			break
		}

		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		gc.Naddr(a, n)
		return true

	case gc.ODOT,
		gc.ODOTPTR:
		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		var nn *gc.Node
		var oary [10]int64
		o := gc.Dotoffset(n, oary[:], &nn)
		if nn == nil {
			sudoclean()
			return false
		}

		if nn.Addable && o == 1 && oary[0] >= 0 {
			// directly addressable set of DOTs
			n1 := *nn

			n1.Type = n.Type
			n1.Xoffset += oary[0]
			gc.Naddr(a, &n1)
			return true
		}

		gc.Regalloc(reg, gc.Types[gc.Tptr], nil)
		n1 := *reg
		n1.Op = gc.OINDREG
		if oary[0] >= 0 {
			gc.Agen(nn, reg)
			n1.Xoffset = oary[0]
		} else {
			gc.Cgen(nn, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[0] + 1)
		}

		for i := 1; i < o; i++ {
			if oary[i] >= 0 {
				gc.Fatal("can't happen")
			}
			gins(movptr, &n1, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[i] + 1)
		}

		a.Type = obj.TYPE_NONE
		a.Index = obj.TYPE_NONE
		gc.Fixlargeoffset(&n1)
		gc.Naddr(a, &n1)
		return true

	case gc.OINDEX:
		return false
	}

	return false
}
Ejemplo n.º 13
0
Archivo: gsubr.go Proyecto: Greentor/go
/*
 * generate code to compute address of n,
 * a reference to a (perhaps nested) field inside
 * an array or struct.
 * return 0 on failure, 1 on success.
 * on success, leaves usable address in a.
 *
 * caller is responsible for calling sudoclean
 * after successful sudoaddable,
 * to release the register used for a.
 */
func sudoaddable(as obj.As, n *gc.Node, a *obj.Addr) bool {
	if n.Type == nil {
		return false
	}

	*a = obj.Addr{}

	switch n.Op {
	case gc.OLITERAL:
		if !gc.Isconst(n, gc.CTINT) {
			return false
		}
		v := n.Int64()
		switch as {
		default:
			return false

		// operations that can cope with a 32-bit immediate
		// TODO(mundaym): logical operations can work on high bits
		case s390x.AADD,
			s390x.AADDC,
			s390x.ASUB,
			s390x.AMULLW,
			s390x.AAND,
			s390x.AOR,
			s390x.AXOR,
			s390x.ASLD,
			s390x.ASLW,
			s390x.ASRAW,
			s390x.ASRAD,
			s390x.ASRW,
			s390x.ASRD,
			s390x.AMOVB,
			s390x.AMOVBZ,
			s390x.AMOVH,
			s390x.AMOVHZ,
			s390x.AMOVW,
			s390x.AMOVWZ,
			s390x.AMOVD:
			if int64(int32(v)) != v {
				return false
			}

		// for comparisons avoid immediates unless they can
		// fit into a int8/uint8
		// this favours combined compare and branch instructions
		case s390x.ACMP:
			if int64(int8(v)) != v {
				return false
			}
		case s390x.ACMPU:
			if int64(uint8(v)) != v {
				return false
			}
		}

		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		gc.Naddr(a, n)
		return true

	case gc.ODOT,
		gc.ODOTPTR:
		cleani += 2
		reg := &clean[cleani-1]
		reg1 := &clean[cleani-2]
		reg.Op = gc.OEMPTY
		reg1.Op = gc.OEMPTY
		var nn *gc.Node
		var oary [10]int64
		o := gc.Dotoffset(n, oary[:], &nn)
		if nn == nil {
			sudoclean()
			return false
		}

		if nn.Addable && o == 1 && oary[0] >= 0 {
			// directly addressable set of DOTs
			n1 := *nn

			n1.Type = n.Type
			n1.Xoffset += oary[0]
			// check that the offset fits into a 12-bit displacement
			if n1.Xoffset < 0 || n1.Xoffset >= (1<<12)-8 {
				sudoclean()
				return false
			}
			gc.Naddr(a, &n1)
			return true
		}

		gc.Regalloc(reg, gc.Types[gc.Tptr], nil)
		n1 := *reg
		n1.Op = gc.OINDREG
		if oary[0] >= 0 {
			gc.Agen(nn, reg)
			n1.Xoffset = oary[0]
		} else {
			gc.Cgen(nn, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[0] + 1)
		}

		for i := 1; i < o; i++ {
			if oary[i] >= 0 {
				gc.Fatalf("can't happen")
			}
			gins(s390x.AMOVD, &n1, reg)
			gc.Cgen_checknil(reg)
			n1.Xoffset = -(oary[i] + 1)
		}

		a.Type = obj.TYPE_NONE
		a.Index = 0
		// check that the offset fits into a 12-bit displacement
		if n1.Xoffset < 0 || n1.Xoffset >= (1<<12)-8 {
			tmp := n1
			tmp.Op = gc.OREGISTER
			tmp.Type = gc.Types[gc.Tptr]
			tmp.Xoffset = 0
			gc.Cgen_checknil(&tmp)
			ginscon(s390x.AADD, n1.Xoffset, &tmp)
			n1.Xoffset = 0
		}
		gc.Naddr(a, &n1)
		return true
	}

	return false
}
Ejemplo n.º 14
0
Archivo: cgen.go Proyecto: 2thetop/go
// blockcopy copies w bytes from &n to &res
func blockcopy(n, res *gc.Node, osrc, odst, w int64) {
	var dst gc.Node
	var src gc.Node
	if n.Ullman >= res.Ullman {
		gc.Agenr(n, &dst, res) // temporarily use dst
		gc.Regalloc(&src, gc.Types[gc.Tptr], nil)
		gins(s390x.AMOVD, &dst, &src)
		if res.Op == gc.ONAME {
			gc.Gvardef(res)
		}
		gc.Agen(res, &dst)
	} else {
		if res.Op == gc.ONAME {
			gc.Gvardef(res)
		}
		gc.Agenr(res, &dst, res)
		gc.Agenr(n, &src, nil)
	}
	defer gc.Regfree(&src)
	defer gc.Regfree(&dst)

	var tmp gc.Node
	gc.Regalloc(&tmp, gc.Types[gc.Tptr], nil)
	defer gc.Regfree(&tmp)

	offset := int64(0)
	dir := _FORWARDS
	if osrc < odst && odst < osrc+w {
		// Reverse. Can't use MVC, fall back onto basic moves.
		dir = _BACKWARDS
		const copiesPerIter = 2
		if w >= 8*copiesPerIter {
			cnt := w - (w % (8 * copiesPerIter))
			ginscon(s390x.AADD, w, &src)
			ginscon(s390x.AADD, w, &dst)

			var end gc.Node
			gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
			p := gins(s390x.ASUB, nil, &end)
			p.From.Type = obj.TYPE_CONST
			p.From.Offset = cnt
			p.Reg = src.Reg

			var label *obj.Prog
			for i := 0; i < copiesPerIter; i++ {
				offset := int64(-8 * (i + 1))
				p := gins(s390x.AMOVD, &src, &tmp)
				p.From.Type = obj.TYPE_MEM
				p.From.Offset = offset
				if i == 0 {
					label = p
				}
				p = gins(s390x.AMOVD, &tmp, &dst)
				p.To.Type = obj.TYPE_MEM
				p.To.Offset = offset
			}

			ginscon(s390x.ASUB, 8*copiesPerIter, &src)
			ginscon(s390x.ASUB, 8*copiesPerIter, &dst)
			gins(s390x.ACMP, &src, &end)
			gc.Patch(gc.Gbranch(s390x.ABNE, nil, 0), label)
			gc.Regfree(&end)

			w -= cnt
		} else {
			offset = w
		}
	}

	if dir == _FORWARDS && w > 1024 {
		// Loop over MVCs
		cnt := w - (w % 256)

		var end gc.Node
		gc.Regalloc(&end, gc.Types[gc.Tptr], nil)
		add := gins(s390x.AADD, nil, &end)
		add.From.Type = obj.TYPE_CONST
		add.From.Offset = cnt
		add.Reg = src.Reg

		mvc := gins(s390x.AMVC, &src, &dst)
		mvc.From.Type = obj.TYPE_MEM
		mvc.From.Offset = 0
		mvc.To.Type = obj.TYPE_MEM
		mvc.To.Offset = 0
		mvc.From3 = new(obj.Addr)
		mvc.From3.Type = obj.TYPE_CONST
		mvc.From3.Offset = 256

		ginscon(s390x.AADD, 256, &src)
		ginscon(s390x.AADD, 256, &dst)
		gins(s390x.ACMP, &src, &end)
		gc.Patch(gc.Gbranch(s390x.ABNE, nil, 0), mvc)
		gc.Regfree(&end)

		w -= cnt
	}

	for w > 0 {
		cnt := w
		// If in reverse we can only do 8, 4, 2 or 1 bytes at a time.
		if dir == _BACKWARDS {
			switch {
			case cnt >= 8:
				cnt = 8
			case cnt >= 4:
				cnt = 4
			case cnt >= 2:
				cnt = 2
			}
		} else if cnt > 256 {
			cnt = 256
		}

		switch cnt {
		case 8, 4, 2, 1:
			op := s390x.AMOVB
			switch cnt {
			case 8:
				op = s390x.AMOVD
			case 4:
				op = s390x.AMOVW
			case 2:
				op = s390x.AMOVH
			}
			load := gins(op, &src, &tmp)
			load.From.Type = obj.TYPE_MEM
			load.From.Offset = offset

			store := gins(op, &tmp, &dst)
			store.To.Type = obj.TYPE_MEM
			store.To.Offset = offset

			if dir == _BACKWARDS {
				load.From.Offset -= cnt
				store.To.Offset -= cnt
			}

		default:
			p := gins(s390x.AMVC, &src, &dst)
			p.From.Type = obj.TYPE_MEM
			p.From.Offset = offset
			p.To.Type = obj.TYPE_MEM
			p.To.Offset = offset
			p.From3 = new(obj.Addr)
			p.From3.Type = obj.TYPE_CONST
			p.From3.Offset = cnt
		}

		switch dir {
		case _FORWARDS:
			offset += cnt
		case _BACKWARDS:
			offset -= cnt
		}
		w -= cnt
	}
}
Ejemplo n.º 15
0
Archivo: cgen.go Proyecto: Greentor/go
func blockcopy(n, res *gc.Node, osrc, odst, w int64) {
	var dst gc.Node
	gc.Nodreg(&dst, gc.Types[gc.Tptr], x86.REG_DI)
	var src gc.Node
	gc.Nodreg(&src, gc.Types[gc.Tptr], x86.REG_SI)

	var tsrc gc.Node
	gc.Tempname(&tsrc, gc.Types[gc.Tptr])
	var tdst gc.Node
	gc.Tempname(&tdst, gc.Types[gc.Tptr])
	if !n.Addable {
		gc.Agen(n, &tsrc)
	}
	if !res.Addable {
		gc.Agen(res, &tdst)
	}
	if n.Addable {
		gc.Agen(n, &src)
	} else {
		gmove(&tsrc, &src)
	}

	if res.Op == gc.ONAME {
		gc.Gvardef(res)
	}

	if res.Addable {
		gc.Agen(res, &dst)
	} else {
		gmove(&tdst, &dst)
	}

	c := int32(w % 4) // bytes
	q := int32(w / 4) // doublewords

	// if we are copying forward on the stack and
	// the src and dst overlap, then reverse direction
	if osrc < odst && odst < osrc+w {
		// reverse direction
		gins(x86.ASTD, nil, nil) // set direction flag
		if c > 0 {
			gconreg(x86.AADDL, w-1, x86.REG_SI)
			gconreg(x86.AADDL, w-1, x86.REG_DI)

			gconreg(x86.AMOVL, int64(c), x86.REG_CX)
			gins(x86.AREP, nil, nil)   // repeat
			gins(x86.AMOVSB, nil, nil) // MOVB *(SI)-,*(DI)-
		}

		if q > 0 {
			if c > 0 {
				gconreg(x86.AADDL, -3, x86.REG_SI)
				gconreg(x86.AADDL, -3, x86.REG_DI)
			} else {
				gconreg(x86.AADDL, w-4, x86.REG_SI)
				gconreg(x86.AADDL, w-4, x86.REG_DI)
			}

			gconreg(x86.AMOVL, int64(q), x86.REG_CX)
			gins(x86.AREP, nil, nil)   // repeat
			gins(x86.AMOVSL, nil, nil) // MOVL *(SI)-,*(DI)-
		}

		// we leave with the flag clear
		gins(x86.ACLD, nil, nil)
	} else {
		gins(x86.ACLD, nil, nil) // paranoia.  TODO(rsc): remove?

		// normal direction
		if q > 128 || (q >= 4 && gc.Nacl) {
			gconreg(x86.AMOVL, int64(q), x86.REG_CX)
			gins(x86.AREP, nil, nil)   // repeat
			gins(x86.AMOVSL, nil, nil) // MOVL *(SI)+,*(DI)+
		} else if q >= 4 {
			p := gins(obj.ADUFFCOPY, nil, nil)
			p.To.Type = obj.TYPE_ADDR
			p.To.Sym = gc.Linksym(gc.Pkglookup("duffcopy", gc.Runtimepkg))

			// 10 and 128 = magic constants: see ../../runtime/asm_386.s
			p.To.Offset = 10 * (128 - int64(q))
		} else if !gc.Nacl && c == 0 {
			var cx gc.Node
			gc.Nodreg(&cx, gc.Types[gc.TINT32], x86.REG_CX)

			// We don't need the MOVSL side-effect of updating SI and DI,
			// and issuing a sequence of MOVLs directly is faster.
			src.Op = gc.OINDREG

			dst.Op = gc.OINDREG
			for q > 0 {
				gmove(&src, &cx) // MOVL x+(SI),CX
				gmove(&cx, &dst) // MOVL CX,x+(DI)
				src.Xoffset += 4
				dst.Xoffset += 4
				q--
			}
		} else {
			for q > 0 {
				gins(x86.AMOVSL, nil, nil) // MOVL *(SI)+,*(DI)+
				q--
			}
		}

		for c > 0 {
			gins(x86.AMOVSB, nil, nil) // MOVB *(SI)+,*(DI)+
			c--
		}
	}
}