cmd/dist: re-enable GOARM auto-detection

cmd/dist will re-exec itself to detect VFP support at run-time.

Fixes #9732, #12548.

Change-Id: I9ad0c5c7fa3e97bd79a32da372e1a962565bb3af
Reviewed-on: https://go-review.googlesource.com/3973
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

diff --git a/src/cmd/dist/util.go b/src/cmd/dist/util.go
index f13210f4dea731b93a10ae8ea0cbda08aee1f9d8..34cbf50282faa3d05bcfe5aac875656d85ed1d6a 100644 (file)
--- a/src/cmd/dist/util.go
+++ b/src/cmd/dist/util.go
@@ -480,6 +480,14 @@ func main() {
                }
        }
 
+       if len(os.Args) > 1 && os.Args[1] == "-check-goarm" {
+               useVFPv1() // might fail with SIGILL
+               println("VFPv1 OK.")
+               useVFPv3() // might fail with SIGILL
+               println("VFPv3 OK.")
+               os.Exit(0)
+       }
+
        xinit()
        xmain()
        xexit(0)
@@ -515,40 +523,21 @@ func xgetgoarm() string {
                // OpenBSD currently only supports softfloat.
                return "5"
        }
-       if goos != "linux" {
-               // All other arm platforms that we support
-               // require ARMv7.
+
+       // Try to exec ourselves in a mode to detect VFP support.
+       // Seeing how far it gets determines which instructions failed.
+       // The test is OS-agnostic.
+       out := run("", 0, os.Args[0], "-check-goarm")
+       v1ok := strings.Contains(out, "VFPv1 OK.")
+       v3ok := strings.Contains(out, "VFPv3 OK.")
+
+       if v1ok && v3ok {
                return "7"
        }
-       cpuinfo := readfile("/proc/cpuinfo")
-       goarm := "5"
-       for _, line := range splitlines(cpuinfo) {
-               line := strings.SplitN(line, ":", 2)
-               if len(line) < 2 {
-                       continue
-               }
-               if strings.TrimSpace(line[0]) != "Features" {
-                       continue
-               }
-               features := splitfields(line[1])
-               sort.Strings(features) // so vfpv3 sorts after vfp
-
-               // Infer GOARM value from the vfp features available
-               // on this host. Values of GOARM detected are:
-               // 5: no vfp support was found
-               // 6: vfp (v1) support was detected, but no higher
-               // 7: vfpv3 support was detected.
-               // This matches the assertions in runtime.checkarm.
-               for _, f := range features {
-                       switch f {
-                       case "vfp":
-                               goarm = "6"
-                       case "vfpv3":
-                               goarm = "7"
-                       }
-               }
+       if v1ok {
+               return "6"
        }
-       return goarm
+       return "5"
 }
 
 func min(a, b int) int {

diff --git a/src/cmd/dist/util_gc.go b/src/cmd/dist/util_gc.go
index 9f6cfd01b79c20518e327653c04d881c09979a6c..81e52b6fb454d9f9c65b65658a339f05f6f5acad 100644 (file)
--- a/src/cmd/dist/util_gc.go
+++ b/src/cmd/dist/util_gc.go
@@ -17,3 +17,11 @@ func cansse2() bool {
        cpuid(&info, 1)
        return info[3]&(1<<26) != 0 // SSE2
 }
+
+// useVFPv1 tries to execute one VFPv1 instruction on ARM.
+// It will crash the current process if VFPv1 is missing.
+func useVFPv1()
+
+// useVFPv3 tries to execute one VFPv3 instruction on ARM.
+// It will crash the current process if VFPv3 is missing.
+func useVFPv3()

diff --git a/src/cmd/dist/util_gccgo.go b/src/cmd/dist/util_gccgo.go
index 14ac70bca5d8eee4e474a54048d40279f2f48cdd..18e328f81a1b46965143432c794639367c7c32a7 100644 (file)
--- a/src/cmd/dist/util_gccgo.go
+++ b/src/cmd/dist/util_gccgo.go
@@ -18,3 +18,7 @@ int supports_sse2() {
 import "C"
 
 func cansse2() bool { return C.supports_sse2() != 0 }
+
+func useVFPv1() {}
+
+func useVFPv3() {}

diff --git a/src/cmd/dist/vfp_arm.s b/src/cmd/dist/vfp_arm.s
new file mode 100644 (file)
index 0000000..647c439
--- /dev/null
+++ b/src/cmd/dist/vfp_arm.s
@@ -0,0 +1,17 @@
+// Copyright 2015 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.
+
+// +build gc,arm
+
+#include "textflag.h"
+
+// try to run "vmov.f64 d0, d0" instruction
+TEXT ·useVFPv1(SB),NOSPLIT,$0
+       WORD $0xeeb00b40        // vmov.f64 d0, d0
+       RET
+
+// try to run VFPv3-only "vmov.f64 d0, #112" instruction
+TEXT ·useVFPv3(SB),NOSPLIT,$0
+       WORD $0xeeb70b00        // vmov.f64 d0, #112
+       RET

diff --git a/src/cmd/dist/vfp_default.s b/src/cmd/dist/vfp_default.s
new file mode 100644 (file)
index 0000000..5cf9997
--- /dev/null
+++ b/src/cmd/dist/vfp_default.s
@@ -0,0 +1,13 @@
+// Copyright 2015 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.
+
+// +build !arm,gc
+
+#include "textflag.h"
+
+TEXT ·useVFPv1(SB),NOSPLIT,$0
+       RET
+
+TEXT ·useVFPv3(SB),NOSPLIT,$0
+       RET