all: replace runtime SSE2 detection with GO386 setting

When GO386=sse2 we can assume sse2 to be present without
a runtime check. If GO386=softfloat is set we can avoid
the usage of SSE2 even if detected.

This might cause a memcpy, memclr and bytealg slowdown of Go
binaries compiled with softfloat on machines that support
SSE2. Such setups are rare and should use GO386=sse2 instead
if performance matters.

On targets that support SSE2 we avoid the runtime overhead of
dynamic cpu feature dispatch.

The removal of runtime sse2 checks also allows to simplify
internal/cpu further by removing handling of the required
feature option as a followup after this CL.

Change-Id: I90a853a8853a405cb665497c6d1a86556947ba17
Reviewed-on: https://go-review.googlesource.com/c/go/+/344350
Trust: Martin Möhrmann <martin@golang.org>
Run-TryBot: Martin Möhrmann <martin@golang.org>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/go/internal/work/gc.go b/src/cmd/go/internal/work/gc.go
index 74e14d0065d5dda234295c54ac0699c27e147322..eee8adca94d8bca54436324922ad99c957422034 100644 (file)
--- a/src/cmd/go/internal/work/gc.go
+++ b/src/cmd/go/internal/work/gc.go
@@ -374,6 +374,11 @@ func asmArgs(a *Action, p *load.Package) []interface{} {
                args = append(args, "-compiling-runtime")
        }
 
+       if cfg.Goarch == "386" {
+               // Define GO386_value from cfg.GO386.
+               args = append(args, "-D", "GO386_"+cfg.GO386)
+       }
+
        if cfg.Goarch == "mips" || cfg.Goarch == "mipsle" {
                // Define GOMIPS_value from cfg.GOMIPS.
                args = append(args, "-D", "GOMIPS_"+cfg.GOMIPS)

diff --git a/src/internal/bytealg/bytealg.go b/src/internal/bytealg/bytealg.go
index 6b2b540acc8846ce1707641930e3d185690ab295..ebebce75fe484a0317be60a053c473726b944f72 100644 (file)
--- a/src/internal/bytealg/bytealg.go
+++ b/src/internal/bytealg/bytealg.go
@@ -11,7 +11,6 @@ import (
 
 // Offsets into internal/cpu records for use in assembly.
 const (
-       offsetX86HasSSE2   = unsafe.Offsetof(cpu.X86.HasSSE2)
        offsetX86HasSSE42  = unsafe.Offsetof(cpu.X86.HasSSE42)
        offsetX86HasAVX2   = unsafe.Offsetof(cpu.X86.HasAVX2)
        offsetX86HasPOPCNT = unsafe.Offsetof(cpu.X86.HasPOPCNT)

diff --git a/src/internal/bytealg/compare_386.s b/src/internal/bytealg/compare_386.s
index 0981983d20f313bd5fd2f750afe89b6aab61f8fc..27b660ccf7c526ac70be5f016695cb19238aa19c 100644 (file)
--- a/src/internal/bytealg/compare_386.s
+++ b/src/internal/bytealg/compare_386.s
@@ -36,8 +36,9 @@ TEXT cmpbody<>(SB),NOSPLIT,$0-0
        JEQ     allsame
        CMPL    BP, $4
        JB      small
-       CMPB    internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
-       JNE     mediumloop
+#ifdef GO386_softfloat
+       JMP     mediumloop
+#endif
 largeloop:
        CMPL    BP, $16
        JB      mediumloop

diff --git a/src/internal/bytealg/equal_386.s b/src/internal/bytealg/equal_386.s
index 87233635a927d35cd6018fa692f3081317575eca..58b3cbe3d07194b5eddd4a3ef2f0b5425d8cb485 100644 (file)
--- a/src/internal/bytealg/equal_386.s
+++ b/src/internal/bytealg/equal_386.s
@@ -43,8 +43,9 @@ TEXT memeqbody<>(SB),NOSPLIT,$0-0
 hugeloop:
        CMPL    BX, $64
        JB      bigloop
-       CMPB    internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
-       JNE     bigloop
+#ifdef GO386_softfloat
+       JMP     bigloop
+#endif
        MOVOU   (SI), X0
        MOVOU   (DI), X1
        MOVOU   16(SI), X2

diff --git a/src/internal/cpu/cpu.go b/src/internal/cpu/cpu.go
index a87d8a2314ae2e5820771ad990773ef6be71f425..4f0c5d2896bfa9d13489ddfc3308bc976c6ea132 100644 (file)
--- a/src/internal/cpu/cpu.go
+++ b/src/internal/cpu/cpu.go
@@ -37,7 +37,6 @@ var X86 struct {
        HasPCLMULQDQ bool
        HasPOPCNT    bool
        HasRDTSCP    bool
-       HasSSE2      bool
        HasSSE3      bool
        HasSSSE3     bool
        HasSSE41     bool

diff --git a/src/internal/cpu/cpu_386.go b/src/internal/cpu/cpu_386.go
deleted file mode 100644 (file)
index 561c81f..0000000
--- a/src/internal/cpu/cpu_386.go
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package cpu
-
-const GOARCH = "386"

diff --git a/src/internal/cpu/cpu_amd64.go b/src/internal/cpu/cpu_amd64.go
deleted file mode 100644 (file)
index 9b00153..0000000
--- a/src/internal/cpu/cpu_amd64.go
+++ /dev/null
@@ -1,7 +0,0 @@
-// Copyright 2018 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package cpu
-
-const GOARCH = "amd64"

diff --git a/src/internal/cpu/cpu_x86.go b/src/internal/cpu/cpu_x86.go
index a3f1fb809ab2288731b2725dadbb865b64c1586e..1582e832a45a548362b11f9b8ecfc792e29508fd 100644 (file)
--- a/src/internal/cpu/cpu_x86.go
+++ b/src/internal/cpu/cpu_x86.go
@@ -61,9 +61,6 @@ func doinit() {
                {Name: "sse41", Feature: &X86.HasSSE41},
                {Name: "sse42", Feature: &X86.HasSSE42},
                {Name: "ssse3", Feature: &X86.HasSSSE3},
-
-               // These capabilities should always be enabled on amd64:
-               {Name: "sse2", Feature: &X86.HasSSE2, Required: GOARCH == "amd64"},
        }
 
        maxID, _, _, _ := cpuid(0, 0)
@@ -74,8 +71,7 @@ func doinit() {
 
        maxExtendedFunctionInformation, _, _, _ = cpuid(0x80000000, 0)
 
-       _, _, ecx1, edx1 := cpuid(1, 0)
-       X86.HasSSE2 = isSet(edx1, cpuid_SSE2)
+       _, _, ecx1, _ := cpuid(1, 0)
 
        X86.HasSSE3 = isSet(ecx1, cpuid_SSE3)
        X86.HasPCLMULQDQ = isSet(ecx1, cpuid_PCLMULQDQ)

diff --git a/src/internal/cpu/cpu_x86_test.go b/src/internal/cpu/cpu_x86_test.go
index e3e16cc1612e05955295a965204ca0dc66e497aa..de1c5fb3b06099ac52dd168ea868a840991342ba 100644 (file)
--- a/src/internal/cpu/cpu_x86_test.go
+++ b/src/internal/cpu/cpu_x86_test.go
@@ -10,7 +10,6 @@ package cpu_test
 import (
        . "internal/cpu"
        "os"
-       "runtime"
        "testing"
 )
 
@@ -20,23 +19,6 @@ func TestX86ifAVX2hasAVX(t *testing.T) {
        }
 }
 
-func TestDisableSSE2(t *testing.T) {
-       runDebugOptionsTest(t, "TestSSE2DebugOption", "cpu.sse2=off")
-}
-
-func TestSSE2DebugOption(t *testing.T) {
-       MustHaveDebugOptionsSupport(t)
-
-       if os.Getenv("GODEBUG") != "cpu.sse2=off" {
-               t.Skipf("skipping test: GODEBUG=cpu.sse2=off not set")
-       }
-
-       want := runtime.GOARCH != "386" // SSE2 can only be disabled on 386.
-       if got := X86.HasSSE2; got != want {
-               t.Errorf("X86.HasSSE2 on %s expected %v, got %v", runtime.GOARCH, want, got)
-       }
-}
-
 func TestDisableSSE3(t *testing.T) {
        runDebugOptionsTest(t, "TestSSE3DebugOption", "cpu.sse3=off")
 }

diff --git a/src/runtime/asm_386.s b/src/runtime/asm_386.s
index b7113568223e2a0142c4aa58a1781655872aa1e6..594cd5ed0d9592fad2a2fa38f71accd0b2ef6471 100644 (file)
--- a/src/runtime/asm_386.s
+++ b/src/runtime/asm_386.s
@@ -838,8 +838,9 @@ TEXT runtime·cputicks(SB),NOSPLIT,$0-8
        // When no SSE2 support is present do not enforce any serialization
        // since using CPUID to serialize the instruction stream is
        // very costly.
-       CMPB    internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
-       JNE     rdtsc
+#ifdef GO386_softfloat
+       JMP     rdtsc  // no fence instructions available
+#endif
        CMPB    internal∕cpu·X86+const_offsetX86HasRDTSCP(SB), $1
        JNE     fences
        // Instruction stream serializing RDTSCP is supported.

diff --git a/src/runtime/cpuflags.go b/src/runtime/cpuflags.go
index c5291ce4ee601eb32d780705868378c9a0618b6f..bbe93c5bea2d7e46d752b25ebfca2e7b1640bdd6 100644 (file)
--- a/src/runtime/cpuflags.go
+++ b/src/runtime/cpuflags.go
@@ -15,7 +15,6 @@ const (
        offsetX86HasAVX2   = unsafe.Offsetof(cpu.X86.HasAVX2)
        offsetX86HasERMS   = unsafe.Offsetof(cpu.X86.HasERMS)
        offsetX86HasRDTSCP = unsafe.Offsetof(cpu.X86.HasRDTSCP)
-       offsetX86HasSSE2   = unsafe.Offsetof(cpu.X86.HasSSE2)
 
        offsetARMHasIDIVA = unsafe.Offsetof(cpu.ARM.HasIDIVA)
 

diff --git a/src/runtime/memclr_386.s b/src/runtime/memclr_386.s
index 046c3441198bf5e4c44b29fe524e8e50d9ca17ca..2627792ced076a308a9410204dbbe51a8f0f8c6d 100644 (file)
--- a/src/runtime/memclr_386.s
+++ b/src/runtime/memclr_386.s
@@ -30,8 +30,9 @@ tail:
        JBE     _5through8
        CMPL    BX, $16
        JBE     _9through16
-       CMPB    internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
-       JNE     nosse2
+#ifdef GO386_softfloat
+       JMP     nosse2
+#endif
        PXOR    X0, X0
        CMPL    BX, $32
        JBE     _17through32

diff --git a/src/runtime/memmove_386.s b/src/runtime/memmove_386.s
index 1a43a1f724d7330f001c7fc5636356216ae8812c..389ef8847712e0d8adf982b9e20171118233ec73 100644 (file)
--- a/src/runtime/memmove_386.s
+++ b/src/runtime/memmove_386.s
@@ -55,8 +55,9 @@ tail:
        JBE     move_5through8
        CMPL    BX, $16
        JBE     move_9through16
-       CMPB    internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
-       JNE     nosse2
+#ifdef GO386_softfloat
+       JMP     nosse2
+#endif
        CMPL    BX, $32
        JBE     move_17through32
        CMPL    BX, $64

diff --git a/src/runtime/mkpreempt.go b/src/runtime/mkpreempt.go
index f2b90307cab1ea05755c7f657796ee7e33a93d40..d87446d03618420b828d8733e24e3733acbbcdc8 100644 (file)
--- a/src/runtime/mkpreempt.go
+++ b/src/runtime/mkpreempt.go
@@ -200,6 +200,8 @@ func gen386() {
                l.add("MOVL", reg, 4)
        }
 
+       softfloat := "GO386_softfloat"
+
        // Save SSE state only if supported.
        lSSE := layout{stack: l.stack, sp: "SP"}
        for i := 0; i < 8; i++ {
@@ -209,13 +211,13 @@ func gen386() {
        p("ADJSP $%d", lSSE.stack)
        p("NOP SP")
        l.save()
-       p("CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1\nJNE nosse")
+       p("#ifndef %s", softfloat)
        lSSE.save()
-       label("nosse:")
+       p("#endif")
        p("CALL ·asyncPreempt2(SB)")
-       p("CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1\nJNE nosse2")
+       p("#ifndef %s", softfloat)
        lSSE.restore()
-       label("nosse2:")
+       p("#endif")
        l.restore()
        p("ADJSP $%d", -lSSE.stack)
 

diff --git a/src/runtime/preempt_386.s b/src/runtime/preempt_386.s
index c3a5fa1f361cfb28c653c27c2f764b54031c7aaf..d57bc3d37c061e17d6f5fed474d3005057ad8851 100644 (file)
--- a/src/runtime/preempt_386.s
+++ b/src/runtime/preempt_386.s
@@ -14,8 +14,7 @@ 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
+       #ifndef GO386_softfloat
        MOVUPS X0, 28(SP)
        MOVUPS X1, 44(SP)
        MOVUPS X2, 60(SP)
@@ -24,10 +23,9 @@ TEXT ·asyncPreempt(SB),NOSPLIT|NOFRAME,$0-0
        MOVUPS X5, 108(SP)
        MOVUPS X6, 124(SP)
        MOVUPS X7, 140(SP)
-nosse:
+       #endif
        CALL ·asyncPreempt2(SB)
-       CMPB internal∕cpu·X86+const_offsetX86HasSSE2(SB), $1
-       JNE nosse2
+       #ifndef GO386_softfloat
        MOVUPS 140(SP), X7
        MOVUPS 124(SP), X6
        MOVUPS 108(SP), X5
@@ -36,7 +34,7 @@ nosse:
        MOVUPS 60(SP), X2
        MOVUPS 44(SP), X1
        MOVUPS 28(SP), X0
-nosse2:
+       #endif
        MOVL 24(SP), DI
        MOVL 20(SP), SI
        MOVL 16(SP), BP