From: Cherry Zhang <cherryyz@google.com>
Date: Mon, 22 Feb 2021 22:43:08 +0000 (-0500)
Subject: cmd/compile: correctly use X15 to zero frame
X-Git-Tag: go1.17beta1~1456
X-Git-Url: http://www.git.cypherpunks.su/?a=commitdiff_plain;h=1678829d9555761c0fa6571fd3bcaec016add3d2;p=gostls13.git

cmd/compile: correctly use X15 to zero frame

In CL 288093 we reserve X15 as the zero register and use that to
zero values. It only covered zeroing generated in SSA but missed
zeroing the frame generated late in the compilation. The latter
still uses X0, but now DUFFZERO expects X15, so it doesn't
actually zero the frame. Change it to use X15.

Should fix #44333.

Change-Id: I239d2b78a5f6468bc86b70aecdd294045311759f
Reviewed-on: https://go-review.googlesource.com/c/go/+/295210
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
---

diff --git a/src/cmd/compile/internal/amd64/ggen.go b/src/cmd/compile/internal/amd64/ggen.go
index aefdb14a69..14c3bd1129 100644
--- a/src/cmd/compile/internal/amd64/ggen.go
+++ b/src/cmd/compile/internal/amd64/ggen.go
@@ -56,8 +56,8 @@ func dzDI(b int64) int64 {
 
 func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.Prog {
 	const (
-		ax = 1 << iota
-		x0
+		ax  = 1 << iota // if AX is already zeroed.
+		x15             // if X15 is already zeroed. Note: in new ABI, X15 is always zero.
 	)
 
 	if cnt == 0 {
@@ -85,29 +85,29 @@ func zerorange(pp *objw.Progs, p *obj.Prog, off, cnt int64, state *uint32) *obj.
 		}
 		p = pp.Append(p, x86.AMOVQ, obj.TYPE_REG, x86.REG_AX, 0, obj.TYPE_MEM, x86.REG_SP, off)
 	} else if !isPlan9 && cnt <= int64(8*types.RegSize) {
-		if *state&x0 == 0 {
-			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_REG, x86.REG_X0, 0)
-			*state |= x0
+		if objabi.Regabi_enabled == 0 && *state&x15 == 0 {
+			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_REG, x86.REG_X15, 0)
+			*state |= x15
 		}
 
 		for i := int64(0); i < cnt/16; i++ {
-			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_MEM, x86.REG_SP, off+i*16)
+			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_X0, 0, obj.TYPE_MEM, x86.REG_SP, off+cnt-int64(16))
+			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 !isPlan9 && (cnt <= int64(128*types.RegSize)) {
-		if *state&x0 == 0 {
-			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X0, 0, obj.TYPE_REG, x86.REG_X0, 0)
-			*state |= x0
+		if objabi.Regabi_enabled == 0 && *state&x15 == 0 {
+			p = pp.Append(p, x86.AXORPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_REG, x86.REG_X15, 0)
+			*state |= x15
 		}
 		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_X0, 0, obj.TYPE_MEM, x86.REG_DI, -int64(8))
+			p = pp.Append(p, x86.AMOVUPS, obj.TYPE_REG, x86.REG_X15, 0, obj.TYPE_MEM, x86.REG_DI, -int64(8))
 		}
 	} else {
 		if *state&ax == 0 {