runtime: guard VZEROUPPER on CPU feature

In CL 219131 we inserted a VZEROUPPER instruction on darwin/amd64.
The instruction is not available on pre-AVX machines. Guard it
with CPU feature.

Fixes #37459.

Change-Id: I9a064df277d091be4ee594eda5c7fd8ee323102b
Reviewed-on: https://go-review.googlesource.com/c/go/+/221057
Run-TryBot: Cherry Zhang <[email protected]>
TryBot-Result: Gobot Gobot <[email protected]>
Reviewed-by: Keith Randall <[email protected]>

Author: cherrymui

src/runtime/cpuflags.go

@@ -11,6 +11,7 @@ import (
 
 // Offsets into internal/cpu records for use in assembly.
 const (
+	offsetX86HasAVX  = unsafe.Offsetof(cpu.X86.HasAVX)
 	offsetX86HasAVX2 = unsafe.Offsetof(cpu.X86.HasAVX2)
 	offsetX86HasERMS = unsafe.Offsetof(cpu.X86.HasERMS)
 	offsetX86HasSSE2 = unsafe.Offsetof(cpu.X86.HasSSE2)

src/runtime/mkpreempt.go

@@ -244,23 +244,26 @@ func genAMD64() {
 
 	// TODO: MXCSR register?
 
+	p("PUSHQ BP")
+	p("MOVQ SP, BP")
+	p("// Save flags before clobbering them")
+	p("PUSHFQ")
+	p("// obj doesn't understand ADD/SUB on SP, but does understand ADJSP")
+	p("ADJSP $%d", l.stack)
+	p("// But vet doesn't know ADJSP, so suppress vet stack checking")
+	p("NOP SP")
+
 	// Apparently, the signal handling code path in darwin kernel leaves
 	// the upper bits of Y registers in a dirty state, which causes
 	// many SSE operations (128-bit and narrower) become much slower.
 	// Clear the upper bits to get to a clean state. See issue #37174.
 	// It is safe here as Go code don't use the upper bits of Y registers.
 	p("#ifdef GOOS_darwin")
+	p("CMPB internal∕cpu·X86+const_offsetX86HasAVX(SB), $0")
+	p("JE 2(PC)")
 	p("VZEROUPPER")
 	p("#endif")
 
-	p("PUSHQ BP")
-	p("MOVQ SP, BP")
-	p("// Save flags before clobbering them")
-	p("PUSHFQ")
-	p("// obj doesn't understand ADD/SUB on SP, but does understand ADJSP")
-	p("ADJSP $%d", l.stack)
-	p("// But vet doesn't know ADJSP, so suppress vet stack checking")
-	p("NOP SP")
 	l.save()
 	p("CALL ·asyncPreempt2(SB)")
 	l.restore()

src/runtime/preempt_amd64.s

@@ -4,9 +4,6 @@
 #include "textflag.h"
 
 TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
-	#ifdef GOOS_darwin
-	VZEROUPPER
-	#endif
 	PUSHQ BP
 	MOVQ SP, BP
 	// Save flags before clobbering them
@@ -15,6 +12,11 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
 	ADJSP $368
 	// But vet doesn't know ADJSP, so suppress vet stack checking
 	NOP SP
+	#ifdef GOOS_darwin
+	CMPB internal∕cpu·X86+const_offsetX86HasAVX(SB), $0
+	JE 2(PC)
+	VZEROUPPER
+	#endif
 	MOVQ AX, 0(SP)
 	MOVQ CX, 8(SP)
 	MOVQ DX, 16(SP)