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// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package amd64
import (
"cmd/compile/internal/gc"
"cmd/internal/obj"
"cmd/internal/obj/x86"
)
// no floating point in note handlers on Plan 9
var isPlan9 = obj.GOOS == "plan9"
func defframe(ptxt *obj.Prog) {
// fill in argument size, stack size
ptxt.To.Type = obj.TYPE_TEXTSIZE
ptxt.To.Val = int32(gc.Rnd(gc.Curfn.Type.ArgWidth(), int64(gc.Widthptr)))
frame := uint32(gc.Rnd(gc.Stksize+gc.Maxarg, int64(gc.Widthreg)))
ptxt.To.Offset = int64(frame)
// insert code to zero ambiguously live variables
// so that the garbage collector only sees initialized values
// when it looks for pointers.
p := ptxt
hi := int64(0)
lo := hi
ax := uint32(0)
x0 := uint32(0)
// iterate through declarations - they are sorted in decreasing xoffset order.
for _, n := range gc.Curfn.Func.Dcl {
if !n.Name.Needzero {
continue
}
if n.Class != gc.PAUTO {
gc.Fatalf("needzero class %d", n.Class)
}
if n.Type.Width%int64(gc.Widthptr) != 0 || n.Xoffset%int64(gc.Widthptr) != 0 || n.Type.Width == 0 {
gc.Fatalf("var %L has size %d offset %d", n, int(n.Type.Width), int(n.Xoffset))
}
if lo != hi && n.Xoffset+n.Type.Width >= lo-int64(2*gc.Widthreg) {
// merge with range we already have
lo = n.Xoffset
continue
}
// zero old range
p = zerorange(p, int64(frame), lo, hi, &ax, &x0)
// set new range
hi = n.Xoffset + n.Type.Width
lo = n.Xoffset
}
// zero final range
zerorange(p, int64(frame), lo, hi, &ax, &x0)
}
// DUFFZERO consists of repeated blocks of 4 MOVUPSs + ADD,
// See runtime/mkduff.go.
const (
dzBlocks = 16 // number of MOV/ADD blocks
dzBlockLen = 4 // number of clears per block
dzBlockSize = 19 // size of instructions in a single block
dzMovSize = 4 // size of single MOV instruction w/ offset
dzAddSize = 4 // size of single ADD instruction
dzClearStep = 16 // number of bytes cleared by each MOV instruction
dzClearLen = dzClearStep * dzBlockLen // bytes cleared by one block
dzSize = dzBlocks * dzBlockSize
)
// dzOff returns the offset for a jump into DUFFZERO.
// b is the number of bytes to zero.
func dzOff(b int64) int64 {
off := int64(dzSize)
off -= b / dzClearLen * dzBlockSize
tailLen := b % dzClearLen
if tailLen >= dzClearStep {
off -= dzAddSize + dzMovSize*(tailLen/dzClearStep)
}
return off
}
// duffzeroDI returns the pre-adjustment to DI for a call to DUFFZERO.
// b is the number of bytes to zero.
func dzDI(b int64) int64 {
tailLen := b % dzClearLen
if tailLen < dzClearStep {
return 0
}
tailSteps := tailLen / dzClearStep
return -dzClearStep * (dzBlockLen - tailSteps)
}
func zerorange(p *obj.Prog, frame int64, lo int64, hi int64, ax *uint32, x0 *uint32) *obj.Prog {
cnt := hi - lo
if cnt == 0 {
return p
}
if cnt%int64(gc.Widthreg) != 0 {
// should only happen with nacl
if cnt%int64(gc.Widthptr) != 0 {
gc.Fatalf("zerorange count not a multiple of widthptr %d", cnt)
}
if *ax == 0 {
p = gc.Appendpp(p, x86.AMOVQ, obj.TYPE_CONST, 0, 0, obj.TYPE_REG, x86.REG_AX, 0)
*ax = 1
}
p = gc.Appendpp(p, x86.AMOVL, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_MEM, x86.REG_SP, frame+lo)
lo += int64(gc.Widthptr)
cnt -= int64(gc.Widthptr)
}
if cnt == 8 {
if *ax == 0 {
p = gc.Appendpp(p, x86.AMOVQ, obj.TYPE_CONST, 0, 0, obj.TYPE_REG, x86.REG_AX, 0)
*ax = 1
}
p = gc.Appendpp(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_MEM, x86.REG_SP, frame+lo)
} else if !isPlan9 && cnt <= int64(8*gc.Widthreg) {
if *x0 == 0 {
p = gc.Appendpp(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_REG, x86.REG_X0, 0)
*x0 = 1
}
for i := int64(0); i < cnt/16; i++ {
p = gc.Appendpp(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_SP, frame+lo+i*16)
}
if cnt%16 != 0 {
p = gc.Appendpp(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_SP, frame+lo+cnt-int64(16))
}
} else if !gc.Nacl && !isPlan9 && (cnt <= int64(128*gc.Widthreg)) {
if *x0 == 0 {
p = gc.Appendpp(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_REG, x86.REG_X0, 0)
*x0 = 1
}
p = gc.Appendpp(p, leaptr, obj.TYPE_MEM, x86.REG_SP, frame+lo+dzDI(cnt), obj.TYPE_REG, x86.REG_DI, 0)
p = gc.Appendpp(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_ADDR, 0, dzOff(cnt))
p.To.Sym = gc.Linksym(gc.Pkglookup("duffzero", gc.Runtimepkg))
if cnt%16 != 0 {
p = gc.Appendpp(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_DI, -int64(8))
}
} else {
if *ax == 0 {
p = gc.Appendpp(p, x86.AMOVQ, obj.TYPE_CONST, 0, 0, obj.TYPE_REG, x86.REG_AX, 0)
*ax = 1
}
p = gc.Appendpp(p, x86.AMOVQ, obj.TYPE_CONST, 0, cnt/int64(gc.Widthreg), obj.TYPE_REG, x86.REG_CX, 0)
p = gc.Appendpp(p, leaptr, obj.TYPE_MEM, x86.REG_SP, frame+lo, obj.TYPE_REG, x86.REG_DI, 0)
p = gc.Appendpp(p, x86.AREP, obj.TYPE_NONE, 0, 0, obj.TYPE_NONE, 0, 0)
p = gc.Appendpp(p, x86.ASTOSQ, obj.TYPE_NONE, 0, 0, obj.TYPE_NONE, 0, 0)
}
return p
}
func ginsnop() {
// This is actually not the x86 NOP anymore,
// but at the point where it gets used, AX is dead
// so it's okay if we lose the high bits.
p := gc.Prog(x86.AXCHGL)
p.From.Type = obj.TYPE_REG
p.From.Reg = x86.REG_AX
p.To.Type = obj.TYPE_REG
p.To.Reg = x86.REG_AX
}
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