From 67edc0ed81947a55adbcd0c9d2317abb93ac9510 Mon Sep 17 00:00:00 2001
From: Cherry Zhang <cherryyz@google.com>
Date: Tue, 6 Oct 2020 22:07:15 -0400
Subject: [PATCH] runtime: restore SSE guard in asyncPreempt on 386

So we don't use SSE instructions under GO386=softfloat.

Change-Id: I8ecc92340ee567f84a22501df2543ec041d25ef2
Reviewed-on: https://go-review.googlesource.com/c/go/+/260137
Trust: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>
---
 src/runtime/mkpreempt.go  | 28 ++++++++++++++++++----------
 src/runtime/preempt_386.s |  6 ++++++
 2 files changed, 24 insertions(+), 10 deletions(-)

diff --git a/src/runtime/mkpreempt.go b/src/runtime/mkpreempt.go
index 40683bb9d9..76237bc31b 100644
--- a/src/runtime/mkpreempt.go
+++ b/src/runtime/mkpreempt.go
@@ -189,26 +189,34 @@ func (l *layout) restore() {
 
 func gen386() {
 	p("PUSHFL")
-
-	// Assign stack offsets.
+	// Save general purpose registers.
 	var l = layout{sp: "SP"}
 	for _, reg := range regNames386 {
-		if reg == "SP" {
+		if reg == "SP" || strings.HasPrefix(reg, "X") {
 			continue
 		}
-		if strings.HasPrefix(reg, "X") {
-			l.add("MOVUPS", reg, 16)
-		} else {
-			l.add("MOVL", reg, 4)
-		}
+		l.add("MOVL", reg, 4)
 	}
 
-	p("ADJSP $%d", l.stack)
+	// Save SSE state only if supported.
+	lSSE := layout{stack: l.stack, sp: "SP"}
+	for i := 0; i < 8; i++ {
+		lSSE.add("MOVUPS", fmt.Sprintf("X%d", i), 16)
+	}
+
+	p("ADJSP $%d", lSSE.stack)
 	p("NOP SP")
 	l.save()
+	p("CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1\nJNE nosse")
+	lSSE.save()
+	label("nosse:")
 	p("CALL ·asyncPreempt2(SB)")
+	p("CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1\nJNE nosse2")
+	lSSE.restore()
+	label("nosse2:")
 	l.restore()
-	p("ADJSP $%d", -l.stack)
+	p("ADJSP $%d", -lSSE.stack)
+
 	p("POPFL")
 	p("RET")
 }
diff --git a/src/runtime/preempt_386.s b/src/runtime/preempt_386.s
index 5c9b8ea224..c3a5fa1f36 100644
--- a/src/runtime/preempt_386.s
+++ b/src/runtime/preempt_386.s
@@ -14,6 +14,8 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVL BP, 16(SP)
 	MOVL SI, 20(SP)
 	MOVL DI, 24(SP)
+	CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
+	JNE nosse
 	MOVUPS X0, 28(SP)
 	MOVUPS X1, 44(SP)
 	MOVUPS X2, 60(SP)
@@ -22,7 +24,10 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVUPS X5, 108(SP)
 	MOVUPS X6, 124(SP)
 	MOVUPS X7, 140(SP)
+nosse:
 	CALL ·asyncPreempt2(SB)
+	CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
+	JNE nosse2
 	MOVUPS 140(SP), X7
 	MOVUPS 124(SP), X6
 	MOVUPS 108(SP), X5
@@ -31,6 +36,7 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	MOVUPS 60(SP), X2
 	MOVUPS 44(SP), X1
 	MOVUPS 28(SP), X0
+nosse2:
 	MOVL 24(SP), DI
 	MOVL 20(SP), SI
 	MOVL 16(SP), BP