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cmd/compile: simplify zerorange on amd64

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Get rid of duffzero and large zeroing cases. We only use this code
for small things now.

Change-Id: Idcf330d0ac6433448efa8e32be7eb7f988e10122
Reviewed-on: https://go-review.googlesource.com/c/go/+/678619
Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
Reviewed-by: Keith Randall <khr@google.com>
This commit is contained in:
Keith Randall 2025-06-03 12:36:35 -07:00
parent f8eae7a3c3
commit b10eb1d042
4 changed files with 25 additions and 101 deletions
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106
src/cmd/compile/internal/amd64/ggen.go
View file

@ -5,113 +5,23 @@
package amd64 package amd64
import ( import (
"cmd/compile/internal/ir"
"cmd/compile/internal/objw" "cmd/compile/internal/objw"
"cmd/compile/internal/types"
"cmd/internal/obj" "cmd/internal/obj"
"cmd/internal/obj/x86" "cmd/internal/obj/x86"
) )
// DUFFZERO consists of repeated blocks of 4 MOVUPSs + LEAQ,
// See runtime/mkduff.go.
const (
dzBlocks = 16 // number of MOV/ADD blocks
dzBlockLen = 4 // number of clears per block
dzBlockSize = 23 // size of instructions in a single block
dzMovSize = 5 // size of single MOV instruction w/ offset
dzLeaqSize = 4 // size of single LEAQ 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 -= dzLeaqSize + 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(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.Prog { func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.Prog {
const ( if cnt%8 != 0 {
r13 = 1 << iota // if R13 is already zeroed. panic("zeroed region not aligned")
)
if cnt == 0 {
return p
} }
for cnt >= 16 {
if cnt == 8 { p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off)
off += 16
cnt -= 16
}
if cnt != 0 {
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off) p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off)
} else if cnt <= int64(8*types.RegSize) {
for i := int64(0); i < cnt/16; i++ {
p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off+i*16)
}
if cnt%16 != 0 {
p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_SP, off+cnt-int64(16))
}
} else if cnt <= int64(128*types.RegSize) {
// Save DI to r12. With the amd64 Go register abi, DI can contain
// an incoming parameter, whereas R12 is always scratch.
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_DI, 0, obj.TYPE_REG, x86.REG_R12, 0)
// Emit duffzero call
p = pp.Append(p, leaptr, obj.TYPE_MEM, x86.REG_SP, off+dzDI(cnt), obj.TYPE_REG, x86.REG_DI, 0)
p = pp.Append(p, obj.ADUFFZERO, obj.TYPE_NONE, 0, 0, obj.TYPE_ADDR, 0, dzOff(cnt))
p.To.Sym = ir.Syms.Duffzero
if cnt%16 != 0 {
p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_DI, -int64(8))
}
// Restore DI from r12
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_R12, 0, obj.TYPE_REG, x86.REG_DI, 0)
} else {
// When the register ABI is in effect, at this point in the
// prolog we may have live values in all of RAX,RDI,RCX. Save
// them off to registers before the REPSTOSQ below, then
// restore. Note that R12 and R13 are always available as
// scratch regs; here we also use R15 (this is safe to do
// since there won't be any globals accessed in the prolog).
// See rewriteToUseGot() in obj6.go for more on r15 use.
// Save rax/rdi/rcx
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_DI, 0, obj.TYPE_REG, x86.REG_R12, 0)
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_REG, x86.REG_R13, 0)
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_CX, 0, obj.TYPE_REG, x86.REG_R15, 0)
// Set up the REPSTOSQ and kick it off.
p = pp.Append(p, x86.AXORL, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_REG, x86.REG_AX, 0)
p = pp.Append(p, x86.AMOVQ, obj.TYPE_CONST, 0, cnt/int64(types.RegSize), obj.TYPE_REG, x86.REG_CX, 0)
p = pp.Append(p, leaptr, obj.TYPE_MEM, x86.REG_SP, off, obj.TYPE_REG, x86.REG_DI, 0)
p = pp.Append(p, x86.AREP, obj.TYPE_NONE, 0, 0, obj.TYPE_NONE, 0, 0)
p = pp.Append(p, x86.ASTOSQ, obj.TYPE_NONE, 0, 0, obj.TYPE_NONE, 0, 0)
// Restore rax/rdi/rcx
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_R12, 0, obj.TYPE_REG, x86.REG_DI, 0)
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_R13, 0, obj.TYPE_REG, x86.REG_AX, 0)
p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_R15, 0, obj.TYPE_REG, x86.REG_CX, 0)
// Record the fact that r13 is no longer zero.
*state &= ^uint32(r13)
} }
return p return p
} }

9
src/cmd/compile/internal/amd64/ssa.go
View file

@ -144,6 +144,15 @@ func memIdx(a *obj.Addr, v *ssa.Value) {
// DUFFZERO consists of repeated blocks of 4 MOVUPSs + LEAQ, // DUFFZERO consists of repeated blocks of 4 MOVUPSs + LEAQ,
// See runtime/mkduff.go. // See runtime/mkduff.go.
const (
dzBlocks = 16 // number of MOV/ADD blocks
dzBlockLen = 4 // number of clears per block
dzBlockSize = 23 // size of instructions in a single block
dzMovSize = 5 // size of single MOV instruction w/ offset
dzLeaqSize = 4 // size of single LEAQ instruction
dzClearStep = 16 // number of bytes cleared by each MOV instruction
)
func duffStart(size int64) int64 { func duffStart(size int64) int64 {
x, _ := duff(size) x, _ := duff(size)
return x return x

2
src/cmd/compile/internal/liveness/plive.go
View file

@ -769,7 +769,7 @@ func (lv *Liveness) epilogue() {
// its stack copy is not live. // its stack copy is not live.
continue continue
} }
// Note: zeroing is handled by zeroResults in walk.go. // Note: zeroing is handled by zeroResults in ../ssagen/ssa.go.
livedefer.Set(int32(i)) livedefer.Set(int32(i))
} }
if n.IsOutputParamHeapAddr() { if n.IsOutputParamHeapAddr() {

9
src/cmd/compile/internal/ssagen/arch.go
View file

@ -25,8 +25,13 @@ type ArchInfo struct {
PadFrame func(int64) int64 PadFrame func(int64) int64
// ZeroRange zeroes a range of memory on stack. It is only inserted // ZeroRange zeroes a range of memory the on stack.
// at function entry, and it is ok to clobber registers. // - it is only called at function entry
// - it is ok to clobber (non-arg) registers.
// - currently used only for small things, so it can be simple.
// - pointers to heap-allocated return values
// - open-coded deferred functions
// (Max size in make.bash is 40 bytes.)
ZeroRange func(*objw.Progs, *obj.Prog, int64, int64, *uint32) *obj.Prog ZeroRange func(*objw.Progs, *obj.Prog, int64, int64, *uint32) *obj.Prog
Ginsnop func(*objw.Progs) *obj.Prog Ginsnop func(*objw.Progs) *obj.Prog