From d0712096b32d032b0b83a5eb899a7359a830732b Mon Sep 17 00:00:00 2001
From: Tobias Klauser <tklauser@distanz.ch>
Date: Thu, 12 Apr 2018 10:27:42 +0200
Subject: [PATCH] runtime: use internal/cpu.X86.HasAVX2 instead of support_avx2
MIME-Version: 1.0
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After CL 104636 cpu.X86.HasAVX is set early enough that it can be used
in runtime·memclrNoHeapPointers. Add an offset to use in assembly and
replace the only occurence of support_avx2.

Change-Id: Icada62efeb3e24d71251d55623a8a8602364c9a8
Reviewed-on: https://go-review.googlesource.com/106595
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Ilya Tocar <ilya.tocar@intel.com>
---
 src/runtime/asm_386.s         | 10 +---------
 src/runtime/asm_amd64.s       | 10 +---------
 src/runtime/asm_amd64p32.s    | 10 +---------
 src/runtime/cpuflags_amd64.go | 10 +++++++++-
 src/runtime/memclr_amd64.s    |  3 ++-
 src/runtime/runtime2.go       |  1 -
 6 files changed, 14 insertions(+), 30 deletions(-)

diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index e68f727076..28d045e416 100644
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -184,11 +184,6 @@ eax7:
 	MOVL	$0, CX
 	CPUID
 
-	// If OS support for XMM and YMM is not present
-	// support_avx2 will be set back to false later.
-	TESTL	$(1<<5), BX
-	SETNE	runtime·support_avx2(SB)
-
 	TESTL	$(1<<9), BX // ERMS
 	SETNE	runtime·support_erms(SB)
 
@@ -197,16 +192,13 @@ osavx:
 	// for XMM and YMM OS support.
 #ifndef GOOS_nacl
 	CMPB	runtime·support_osxsave(SB), $1
-	JNE	noavx
+	JNE	nocpuinfo
 	MOVL	$0, CX
 	// For XGETBV, OSXSAVE bit is required and sufficient
 	XGETBV
 	ANDL	$6, AX
 	CMPL	AX, $6 // Check for OS support of XMM and YMM registers.
-	JE nocpuinfo
 #endif
-noavx:
-	MOVB $0, runtime·support_avx2(SB)
 
 nocpuinfo:
 	// if there is an _cgo_init, call it to let it
diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 23b25bb9a4..bfec6ef410 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -147,25 +147,17 @@ eax7:
 	MOVL	$0, CX
 	CPUID
 
-	// If OS support for XMM and YMM is not present
-	// support_avx2 will be set back to false later.
-	TESTL	$(1<<5), BX
-	SETNE	runtime·support_avx2(SB)
-
 	TESTL	$(1<<9), BX // ERMS
 	SETNE	runtime·support_erms(SB)
 
 osavx:
 	CMPB	runtime·support_osxsave(SB), $1
-	JNE	noavx
+	JNE	nocpuinfo
 	MOVL	$0, CX
 	// For XGETBV, OSXSAVE bit is required and sufficient
 	XGETBV
 	ANDL	$6, AX
 	CMPL	AX, $6 // Check for OS support of XMM and YMM registers.
-	JE nocpuinfo
-noavx:
-	MOVB $0, runtime·support_avx2(SB)
 
 nocpuinfo:
 	// if there is an _cgo_init, call it.
diff --git a/src/runtime/asm_amd64p32.s b/src/runtime/asm_amd64p32.s
index 63bf2b07a0..9c0d788ea5 100644
--- a/src/runtime/asm_amd64p32.s
+++ b/src/runtime/asm_amd64p32.s
@@ -67,11 +67,6 @@ eax7:
 	MOVL	$0, CX
 	CPUID
 
-	// If OS support for XMM and YMM is not present
-	// support_avx2 will be set back to false later.
-	TESTL	$(1<<5), BX
-	SETNE	runtime·support_avx2(SB)
-
 	TESTL	$(1<<9), BX // ERMS
 	SETNE	runtime·support_erms(SB)
 
@@ -80,16 +75,13 @@ osavx:
 	// for XMM and YMM OS support.
 #ifndef GOOS_nacl
 	CMPB	runtime·support_osxsave(SB), $1
-	JNE	noavx
+	JNE	nocpuinfo
 	MOVL	$0, CX
 	// For XGETBV, OSXSAVE bit is required and sufficient
 	XGETBV
 	ANDL	$6, AX
 	CMPL	AX, $6 // Check for OS support of XMM and YMM registers.
-	JE nocpuinfo
 #endif
-noavx:
-	MOVB $0, runtime·support_avx2(SB)
 
 nocpuinfo:
 
diff --git a/src/runtime/cpuflags_amd64.go b/src/runtime/cpuflags_amd64.go
index 9d2d4fcbe2..10ab5f5b00 100644
--- a/src/runtime/cpuflags_amd64.go
+++ b/src/runtime/cpuflags_amd64.go
@@ -4,7 +4,15 @@
 
 package runtime
 
-import "internal/cpu"
+import (
+	"internal/cpu"
+	"unsafe"
+)
+
+// Offsets into internal/cpu records for use in assembly.
+const (
+	offsetX86HasAVX2 = unsafe.Offsetof(cpu.X86.HasAVX2)
+)
 
 var useAVXmemmove bool
 
diff --git a/src/runtime/memclr_amd64.s b/src/runtime/memclr_amd64.s
index 244f5b4d8c..d0fd50d4f1 100644
--- a/src/runtime/memclr_amd64.s
+++ b/src/runtime/memclr_amd64.s
@@ -4,6 +4,7 @@
 
 // +build !plan9
 
+#include "go_asm.h"
 #include "textflag.h"
 
 // NOTE: Windows externalthreadhandler expects memclr to preserve DX.
@@ -36,7 +37,7 @@ tail:
 	JBE	_65through128
 	CMPQ	BX, $256
 	JBE	_129through256
-	CMPB	runtime·support_avx2(SB), $1
+	CMPB	internal∕cpu·X86+const_offsetX86HasAVX2(SB), $1
 	JE loop_preheader_avx2
 	// TODO: use branch table and BSR to make this just a single dispatch
 	// TODO: for really big clears, use MOVNTDQ, even without AVX2.
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index 0d253233d2..51fceb8d8f 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -779,7 +779,6 @@ var (
 	processorVersionInfo uint32
 	isIntel              bool
 	lfenceBeforeRdtsc    bool
-	support_avx2         bool
 	support_erms         bool
 	support_osxsave      bool
 	support_popcnt       bool
-- 
2.50.0