runtime, internal/cpu: CPU capabilities detection for ppc64x

This change replaces the current runtime capabilities check for ppc64x with the
new internal/cpu package. It also adds support for the new POWER9 ISA and
capabilities.

Updates #15403

Change-Id: I5b64a79e782f8da3603e5529600434f602986292
Reviewed-on: https://go-review.googlesource.com/53830Reviewed-by: Martin Möhrmann <moehrmann@google.com>

src/internal/cpu/cpu.go

@@ -30,3 +30,28 @@ type x86 struct {
 	HasSSE42     bool
 	_            [CacheLineSize]byte
 }
+
+var PPC64 ppc64
+
+// For ppc64x, it is safe to check only for ISA level starting on ISA v3.00,
+// since there are no optional categories. There are some exceptions that also
+// require kernel support to work (darn, scv), so there are capability bits for
+// those as well. The minimum processor requirement is POWER8 (ISA 2.07), so we
+// maintain some of the old capability checks for optional categories for
+// safety.
+// The struct is padded to avoid false sharing.
+type ppc64 struct {
+	_          [CacheLineSize]byte
+	HasVMX     bool // Vector unit (Altivec)
+	HasDFP     bool // Decimal Floating Point unit
+	HasVSX     bool // Vector-scalar unit
+	HasHTM     bool // Hardware Transactional Memory
+	HasISEL    bool // Integer select
+	HasVCRYPTO bool // Vector cryptography
+	HasHTMNOSC bool // HTM: kernel-aborted transaction in syscalls
+	HasDARN    bool // Hardware random number generator (requires kernel enablement)
+	HasSCV     bool // Syscall vectored (requires kernel enablement)
+	IsPOWER8   bool // ISA v2.07 (POWER8)
+	IsPOWER9   bool // ISA v3.00 (POWER9)
+	_          [CacheLineSize]byte
+}

src/internal/cpu/cpu_ppc64.go

-// Copyright 2017 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 CacheLineSize = 128

src/internal/cpu/cpu_ppc64le.go

-// Copyright 2017 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 CacheLineSize = 128

src/internal/cpu/cpu_ppc64x.go

+// Copyright 2017 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 CacheLineSize = 128
+
+// ppc64x doesn't have a 'cpuid' equivalent, so we rely on HWCAP/HWCAP2.
+// These are linknamed in runtime/os_linux_ppc64x.go and are initialized by
+// archauxv().
+var ppc64x_hwcap uint
+var ppc64x_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_FEATURE_HAS_ALTIVEC     = 0x10000000
+	_PPC_FEATURE_HAS_DFP         = 0x00000400
+	_PPC_FEATURE_HAS_VSX         = 0x00000080
+	_PPC_FEATURE2_HAS_HTM        = 0x40000000
+	_PPC_FEATURE2_HAS_ISEL       = 0x08000000
+	_PPC_FEATURE2_HAS_VEC_CRYPTO = 0x02000000
+	_PPC_FEATURE2_HTM_NOSC       = 0x01000000
+	_PPC_FEATURE2_DARN           = 0x00200000
+	_PPC_FEATURE2_SCV            = 0x00100000
+)
+
+func init() {
+	// HWCAP feature bits
+	PPC64.HasVMX = isSet(ppc64x_hwcap, _PPC_FEATURE_HAS_ALTIVEC)
+	PPC64.HasDFP = isSet(ppc64x_hwcap, _PPC_FEATURE_HAS_DFP)
+	PPC64.HasVSX = isSet(ppc64x_hwcap, _PPC_FEATURE_HAS_VSX)
+
+	// HWCAP2 feature bits
+	PPC64.IsPOWER8 = isSet(ppc64x_hwcap2, _PPC_FEATURE2_ARCH_2_07)
+	PPC64.HasHTM = isSet(ppc64x_hwcap2, _PPC_FEATURE2_HAS_HTM)
+	PPC64.HasISEL = isSet(ppc64x_hwcap2, _PPC_FEATURE2_HAS_ISEL)
+	PPC64.HasVCRYPTO = isSet(ppc64x_hwcap2, _PPC_FEATURE2_HAS_VEC_CRYPTO)
+	PPC64.HasHTMNOSC = isSet(ppc64x_hwcap2, _PPC_FEATURE2_HTM_NOSC)
+	PPC64.IsPOWER9 = isSet(ppc64x_hwcap2, _PPC_FEATURE2_ARCH_3_00)
+	PPC64.HasDARN = isSet(ppc64x_hwcap2, _PPC_FEATURE2_DARN)
+	PPC64.HasSCV = isSet(ppc64x_hwcap2, _PPC_FEATURE2_SCV)
+}
+
+func isSet(hwc uint, value uint) bool {
+	return hwc&value != 0
+}

src/internal/cpu/cpu_test.go

@@ -25,3 +25,26 @@ func TestAVX2hasAVX(t *testing.T) {
 		}
 	}
 }
+
+func TestPPC64minimalFeatures(t *testing.T) {
+	if runtime.GOARCH == "ppc64" || runtime.GOARCH == "ppc64le" {
+		if !cpu.PPC64.IsPOWER8 {
+			t.Fatalf("IsPOWER8 expected true, got false")
+		}
+		if !cpu.PPC64.HasVMX {
+			t.Fatalf("HasVMX expected true, got false")
+		}
+		if !cpu.PPC64.HasDFP {
+			t.Fatalf("HasDFP expected true, got false")
+		}
+		if !cpu.PPC64.HasVSX {
+			t.Fatalf("HasVSX expected true, got false")
+		}
+		if !cpu.PPC64.HasISEL {
+			t.Fatalf("HasISEL expected true, got false")
+		}
+		if !cpu.PPC64.HasVCRYPTO {
+			t.Fatalf("HasVCRYPTO expected true, got false")
+		}
+	}
+}

src/runtime/os_linux_ppc64x.go

@@ -6,55 +6,22 @@
 
 package runtime
 
-import (
-	"runtime/internal/sys"
-)
+// For go:linkname
+import _ "unsafe"
 
-const (
-	// ISA level
-	// Go currently requires POWER5 as a minimum for ppc64, so we need
-	// to check for ISA 2.03 and beyond.
-	_PPC_FEATURE_POWER5_PLUS = 0x00020000 // ISA 2.03 (POWER5+)
-	_PPC_FEATURE_ARCH_2_05   = 0x00001000 // ISA 2.05 (POWER6)
-	_PPC_FEATURE_POWER6_EXT  = 0x00000200 // mffgpr/mftgpr extension (POWER6x)
-	_PPC_FEATURE_ARCH_2_06   = 0x00000100 // ISA 2.06 (POWER7)
-	_PPC_FEATURE2_ARCH_2_07  = 0x80000000 // ISA 2.07 (POWER8)
+// ppc64x doesn't have a 'cpuid' instruction equivalent and relies on
+// HWCAP/HWCAP2 bits for hardware capabilities.
 
-	// Standalone capabilities
-	_PPC_FEATURE_HAS_ALTIVEC = 0x10000000 // SIMD/Vector unit
-	_PPC_FEATURE_HAS_VSX     = 0x00000080 // Vector scalar unit
-)
-
-type facilities struct {
-	_         [sys.CacheLineSize]byte
-	isPOWER5x bool // ISA 2.03
-	isPOWER6  bool // ISA 2.05
-	isPOWER6x bool // ISA 2.05 + mffgpr/mftgpr extension
-	isPOWER7  bool // ISA 2.06
-	isPOWER8  bool // ISA 2.07
-	hasVMX    bool // Vector unit
-	hasVSX    bool // Vector scalar unit
-	_         [sys.CacheLineSize]byte
-}
-
-// cpu can be tested at runtime in go assembler code to check for
-// a certain ISA level or hardware capability, for example:
-//	  ·cpu+facilities_hasVSX(SB) for checking the availability of VSX
-//	  or
-//	  ·cpu+facilities_isPOWER7(SB) for checking if the processor implements
-//	  ISA 2.06 instructions.
-var cpu facilities
+//go:linkname cpu_hwcap internal/cpu.ppc64x_hwcap
+//go:linkname cpu_hwcap2 internal/cpu.ppc64x_hwcap2
+var cpu_hwcap uint
+var cpu_hwcap2 uint
 
 func archauxv(tag, val uintptr) {
 	switch tag {
 	case _AT_HWCAP:
-		cpu.isPOWER5x = val&_PPC_FEATURE_POWER5_PLUS != 0
-		cpu.isPOWER6 = val&_PPC_FEATURE_ARCH_2_05 != 0
-		cpu.isPOWER6x = val&_PPC_FEATURE_POWER6_EXT != 0
-		cpu.isPOWER7 = val&_PPC_FEATURE_ARCH_2_06 != 0
-		cpu.hasVMX = val&_PPC_FEATURE_HAS_ALTIVEC != 0
-		cpu.hasVSX = val&_PPC_FEATURE_HAS_VSX != 0
+		cpu_hwcap = uint(val)
 	case _AT_HWCAP2:
-		cpu.isPOWER8 = val&_PPC_FEATURE2_ARCH_2_07 != 0
+		cpu_hwcap2 = uint(val)
 	}
 }