runtime: get s390x vector facility availability from AT_HWCAP

This is a more robust method for obtaining the availability of vx.
Since this variable may be checked frequently I've also now
padded it so that it will be in its own cache line.

I've kept the other check (in hash/crc32) the same for now until
I can figure out the best way to update it.

Updates #15403.

Change-Id: I74eed651afc6f6a9c5fa3b88fa6a2b0c9ecf5875
Reviewed-on: https://go-review.googlesource.com/31149
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/runtime/asm_s390x.s b/src/runtime/asm_s390x.s
index 9ed4d9186805820b9797495379071141dc4ebac0..d8f529ef906e85bb950a8b4c7743d2496406f937 100644 (file)
--- a/src/runtime/asm_s390x.s
+++ b/src/runtime/asm_s390x.s
@@ -7,44 +7,6 @@
 #include "funcdata.h"
 #include "textflag.h"
 
-// Indicate the status of vector facility
-// -1:         init value
-// 0:  vector not installed
-// 1:  vector installed and enabled
-// 2:  vector installed but not enabled
-
-DATA runtime·vectorfacility+0x00(SB)/4, $-1
-GLOBL runtime·vectorfacility(SB), NOPTR, $4
-
-TEXT runtime·checkvectorfacility(SB),NOSPLIT,$32-0
-       MOVD    $2, R0
-       MOVD    R1, tmp-32(SP)
-       MOVD    $x-24(SP), R1
-       XC      $24, 0(R1), 0(R1)
-//      STFLE   0(R1)
-       WORD    $0xB2B01000
-       MOVBZ   z-8(SP), R1
-       AND     $0x40, R1
-       BNE     vectorinstalled
-       MOVB    $0, runtime·vectorfacility(SB) //Vector not installed
-       MOVD    tmp-32(SP), R1
-       MOVD    $0, R0
-       RET
-vectorinstalled:
-       // check if the vector instruction has been enabled
-       VLEIB   $0, $0xF, V16
-       VLGVB   $0, V16, R0
-       CMPBEQ  R0, $0xF, vectorenabled
-       MOVB    $2, runtime·vectorfacility(SB) //Vector installed but not enabled
-       MOVD    tmp-32(SP), R1
-       MOVD    $0, R0
-       RET
-vectorenabled:
-       MOVB    $1, runtime·vectorfacility(SB) //Vector installed and enabled
-       MOVD    tmp-32(SP), R1
-       MOVD    $0, R0
-       RET
-
 TEXT runtime·rt0_go(SB),NOSPLIT,$0
        // R2 = argc; R3 = argv; R11 = temp; R13 = g; R15 = stack pointer
        // C TLS base pointer in AR0:AR1
@@ -888,14 +850,14 @@ TEXT runtime·fastrand(SB), NOSPLIT, $0-4
        MOVW    R3, ret+0(FP)
        RET
 
-TEXT bytes·IndexByte(SB),NOSPLIT,$0-40
+TEXT bytes·IndexByte(SB),NOSPLIT|NOFRAME,$0-40
        MOVD    s+0(FP), R3     // s => R3
        MOVD    s_len+8(FP), R4 // s_len => R4
        MOVBZ   c+24(FP), R5    // c => R5
        MOVD    $ret+32(FP), R2 // &ret => R9
        BR      runtime·indexbytebody(SB)
 
-TEXT strings·IndexByte(SB),NOSPLIT,$0-32
+TEXT strings·IndexByte(SB),NOSPLIT|NOFRAME,$0-32
        MOVD    s+0(FP), R3     // s => R3
        MOVD    s_len+8(FP), R4 // s_len => R4
        MOVBZ   c+16(FP), R5    // c => R5
@@ -907,7 +869,7 @@ TEXT strings·IndexByte(SB),NOSPLIT,$0-32
 // R4: s_len
 // R5: c -- byte sought
 // R2: &ret -- address to put index into
-TEXT runtime·indexbytebody(SB),NOSPLIT,$0
+TEXT runtime·indexbytebody(SB),NOSPLIT|NOFRAME,$0
        CMPBEQ  R4, $0, notfound
        MOVD    R3, R6          // store base for later
        ADD     R3, R4, R8      // the address after the end of the string
@@ -931,12 +893,10 @@ notfound:
        RET
 
 large:
-       MOVB    runtime·vectorfacility(SB), R1
-       CMPBEQ  R1, $-1, checkvector    // vectorfacility = -1, vector not checked yet
-vectorchecked:
-       CMPBEQ  R1, $1, vectorimpl      // vectorfacility = 1, vector supported
+       MOVBZ   ·cpu+facilities_hasVX(SB), R1
+       CMPBNE  R1, $0, vectorimpl
 
-srstimpl:                       // vectorfacility != 1, not support or enable vector
+srstimpl:                       // no vector facility
        MOVBZ   R5, R0          // c needs to be in R0, leave until last minute as currently R0 is expected to be 0
 srstloop:
        WORD    $0xB25E0083     // srst %r8, %r3 (search the range [R3, R8))
@@ -989,11 +949,6 @@ notalignedloop:
        CMPBNE  R7, R5, notalignedloop
        BR      found
 
-checkvector:
-       CALL    runtime·checkvectorfacility(SB)
-       MOVB    runtime·vectorfacility(SB), R1
-       BR      vectorchecked
-
 TEXT runtime·return0(SB), NOSPLIT, $0
        MOVW    $0, R3
        RET

diff --git a/src/runtime/os_linux.go b/src/runtime/os_linux.go
index 1adabe1a42b3e2b6135045322c4e9a3caeefad2d..4fae7aafcbc90fb92a45dc0967282a95c54387e6 100644 (file)
--- a/src/runtime/os_linux.go
+++ b/src/runtime/os_linux.go
@@ -182,6 +182,7 @@ var failthreadcreate = []byte("runtime: failed to create new OS thread\n")
 const (
        _AT_NULL   = 0  // End of vector
        _AT_PAGESZ = 6  // System physical page size
+       _AT_HWCAP  = 16 // hardware capability bit vector
        _AT_RANDOM = 25 // introduced in 2.6.29
 )
 

diff --git a/src/runtime/os_linux_arm.go b/src/runtime/os_linux_arm.go
index d7d734bc7ff4241e626098583cce67a10f718d5e..2b0834a5aa9dd5d539dad1bfee166973cedb4c8b 100644 (file)
--- a/src/runtime/os_linux_arm.go
+++ b/src/runtime/os_linux_arm.go
@@ -8,7 +8,6 @@ import "unsafe"
 
 const (
        _AT_PLATFORM = 15 //  introduced in at least 2.6.11
-       _AT_HWCAP    = 16 // introduced in at least 2.6.11
 
        _HWCAP_VFP   = 1 << 6  // introduced in at least 2.6.11
        _HWCAP_VFPv3 = 1 << 13 // introduced in 2.6.30

diff --git a/src/runtime/os_linux_noauxv.go b/src/runtime/os_linux_noauxv.go
index 22522dd803dc02704b9e27c91c1bd9027689a5d0..8f26589e0b07bf4fb53ed5285cf0054357071913 100644 (file)
--- a/src/runtime/os_linux_noauxv.go
+++ b/src/runtime/os_linux_noauxv.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// +build !amd64,!arm,!arm64,!mips64,!mips64le
+// +build !amd64,!arm,!arm64,!mips64,!mips64le,!s390x
 
 package runtime
 

diff --git a/src/runtime/os_linux_s390x.go b/src/runtime/os_linux_s390x.go
new file mode 100644 (file)
index 0000000..3ca6d4c
--- /dev/null
+++ b/src/runtime/os_linux_s390x.go
@@ -0,0 +1,32 @@
+// Copyright 2016 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 runtime
+
+import (
+       "runtime/internal/sys"
+)
+
+const (
+       // bit masks taken from bits/hwcap.h
+       _HWCAP_S390_VX = 2048 // vector facility
+)
+
+// facilities is padded to avoid false sharing.
+type facilities struct {
+       _     [sys.CacheLineSize]byte
+       hasVX bool // vector facility
+       _     [sys.CacheLineSize]byte
+}
+
+// cpu indicates the availability of s390x facilities that can be used in
+// Go assembly but are optional on models supported by Go.
+var cpu facilities
+
+func archauxv(tag, val uintptr) {
+       switch tag {
+       case _AT_HWCAP: // CPU capability bit flags
+               cpu.hasVX = val&_HWCAP_S390_VX != 0
+       }
+}