runtime: move ppc64/aix cpu feature detection to internal/cpu

Additionally removed unused PPC64.IsPOWER8 CPU feature detection.

Change-Id: I1411b03d396a72e08d6d51f8a1d1bad49eaa720e
Reviewed-on: https://go-review.googlesource.com/c/go/+/266077
Trust: Martin Möhrmann <moehrmann@google.com>
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>

src/internal/cpu/cpu.s

@@ -0,0 +1,6 @@
+// Copyright 2020 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.
+
+// This assembly file exists to allow internal/cpu to call
+// non-exported runtime functions that use "go:linkname".

src/internal/cpu/cpu_ppc64x.go

@@ -8,39 +8,14 @@ package cpu
 
 const CacheLinePadSize = 128
 
-// ppc64x doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
-// These are initialized by archauxv and should not be changed after they are
-// initialized.
-// On aix/ppc64, these values are initialized early in the runtime in runtime/os_aix.go.
-var HWCap uint
-var HWCap2 uint
-
-// HWCAP/HWCAP2 bits. These are exposed by the kernel.
-const (
-	// ISA Level
-	PPC_FEATURE2_ARCH_2_07 = 0x80000000
-	PPC_FEATURE2_ARCH_3_00 = 0x00800000
-
-	// CPU features
-	PPC_FEATURE2_DARN = 0x00200000
-	PPC_FEATURE2_SCV  = 0x00100000
-)
-
 func doinit() {
 	options = []option{
 		{Name: "darn", Feature: &PPC64.HasDARN},
 		{Name: "scv", Feature: &PPC64.HasSCV},
 		{Name: "power9", Feature: &PPC64.IsPOWER9},
-
-		// These capabilities should always be enabled on ppc64 and ppc64le:
-		{Name: "power8", Feature: &PPC64.IsPOWER8, Required: true},
 	}
 
-	// HWCAP2 feature bits
-	PPC64.IsPOWER8 = isSet(HWCap2, PPC_FEATURE2_ARCH_2_07)
-	PPC64.IsPOWER9 = isSet(HWCap2, PPC_FEATURE2_ARCH_3_00)
-	PPC64.HasDARN = isSet(HWCap2, PPC_FEATURE2_DARN)
-	PPC64.HasSCV = isSet(HWCap2, PPC_FEATURE2_SCV)
+	osinit()
 }
 
 func isSet(hwc uint, value uint) bool {

src/internal/cpu/cpu_ppc64x_aix.go

@@ -0,0 +1,21 @@
+// Copyright 2020 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 ppc64 ppc64le
+
+package cpu
+
+const (
+	// getsystemcfg constants
+	_SC_IMPL     = 2
+	_IMPL_POWER9 = 0x20000
+)
+
+func osinit() {
+	impl := getsystemcfg(_SC_IMPL)
+	PPC64.IsPOWER9 = isSet(impl, _IMPL_POWER9)
+}
+
+// getsystemcfg is defined in runtime/os2_aix.go
+func getsystemcfg(label uint) uint

src/internal/cpu/cpu_ppc64x_linux.go

@@ -0,0 +1,29 @@
+// Copyright 2020 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 ppc64 ppc64le
+
+package cpu
+
+// ppc64 doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
+// These are initialized by archauxv and should not be changed after they are
+// initialized.
+var HWCap uint
+var HWCap2 uint
+
+// HWCAP bits. These are exposed by Linux.
+const (
+	// ISA Level
+	hwcap2_ARCH_3_00 = 0x00800000
+
+	// CPU features
+	hwcap2_DARN = 0x00200000
+	hwcap2_SCV  = 0x00100000
+)
+
+func osinit() {
+	PPC64.IsPOWER9 = isSet(HWCap2, hwcap2_ARCH_3_00)
+	PPC64.HasDARN = isSet(HWCap2, hwcap2_DARN)
+	PPC64.HasSCV = isSet(HWCap2, hwcap2_SCV)
+}

src/runtime/os2_aix.go

@@ -518,9 +518,10 @@ func sigaltstack(new, old *stackt) {
 }
 
 //go:nosplit
-func getsystemcfg(label uint) uintptr {
+//go:linkname internal_cpu_getsystemcfg internal/cpu.getsystemcfg
+func internal_cpu_getsystemcfg(label uint) uint {
 	r, _ := syscall1(&libc_getsystemcfg, uintptr(label))
-	return r
+	return uint(r)
 }
 
 func usleep1(us uint32)

src/runtime/os_aix.go

@@ -7,7 +7,6 @@
 package runtime
 
 import (
-	"internal/cpu"
 	"unsafe"
 )
 
@@ -94,7 +93,6 @@ func semawakeup(mp *m) {
 func osinit() {
 	ncpu = int32(sysconf(__SC_NPROCESSORS_ONLN))
 	physPageSize = sysconf(__SC_PAGE_SIZE)
-	setupSystemConf()
 }
 
 // newosproc0 is a version of newosproc that can be called before the runtime
@@ -340,25 +338,6 @@ func walltime1() (sec int64, nsec int32) {
 	return ts.tv_sec, int32(ts.tv_nsec)
 }
 
-const (
-	// getsystemcfg constants
-	_SC_IMPL     = 2
-	_IMPL_POWER8 = 0x10000
-	_IMPL_POWER9 = 0x20000
-)
-
-// setupSystemConf retrieves information about the CPU and updates
-// cpu.HWCap variables.
-func setupSystemConf() {
-	impl := getsystemcfg(_SC_IMPL)
-	if impl&_IMPL_POWER8 != 0 {
-		cpu.HWCap2 |= cpu.PPC_FEATURE2_ARCH_2_07
-	}
-	if impl&_IMPL_POWER9 != 0 {
-		cpu.HWCap2 |= cpu.PPC_FEATURE2_ARCH_3_00
-	}
-}
-
 //go:nosplit
 func fcntl(fd, cmd, arg int32) int32 {
 	r, _ := syscall3(&libc_fcntl, uintptr(fd), uintptr(cmd), uintptr(arg))