runtime: Handle auxv data for ppc64 and ppc64le

This commit saves the values of AT_HWCAP and AT_HWCAP2 from the auxiliary
vector, so they can be used later for runtime checking the ISA level and
hardware capabilities to enable some instructions. It also defines a few
hwcap/hwcap2 masks that will be commonly used for such runtime checks, and also
provides a function for these verifications.

These checks will be used more often as new POWER8/POWER9 optimizations are
added to the ppc64x runtime, so they do not break compatibility with older
processors.

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,!ppc64,!ppc64le
 
 package runtime
 

src/runtime/os_linux_ppc64.go

@@ -0,0 +1,46 @@
+// 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
+
+const (
+	_AT_HWCAP	  = 16
+	_AT_HWCAP2	  = 26
+
+	// Golang currently requires POWER5 as a minimum for ppc64, so we need
+	// to check for ISA 2.03 and beyond.
+	// Since we support only POWER server processors, we will assume that
+	// each processor generation implements the full ISA — i.e. POWER7
+	// implies VSX support, POWER8 implies HTM support, etc. The only
+	// exception is the POWER6x (ISA 2.05 + mffgpr/mftgpr extension).
+	_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)
+	_PPC_FEATURE2_ARCH_3_00	  = 0x00800000	// ISA 3.0 (POWER9)
+)
+
+var hwcap uint32
+var hwcap2 uint32
+
+// Function for runtime capability checks.
+// mask = hwcap or hwcap2
+// supports = feature mask (see __PPC_FEATURE* constants above)
+func checkppc64supports(mask uint32, supports uint32) bool {
+	if (mask & supports) == 0 {
+		return false
+	} else {
+		return true
+	}
+}
+
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_HWCAP:
+		hwcap = uint32(val)
+	case _AT_HWCAP2:
+		hwcap2 = uint32(val)
+	}
+}

src/runtime/os_linux_ppc64le.go

@@ -0,0 +1,35 @@
+// 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
+
+const (
+	_AT_HWCAP2	  = 26
+
+	// Golang currently requires POWER8 as a minimum for ppc64le. Therefore,
+	// there is no need to check for any capabilities that were introduced
+	// before ISA 2.07 (Altivec/VMX, VSX, DFP, etc). Hence, only HWCAP2 is
+	// required and we start checking from ISA 3.0 and beyond.
+	_PPC_FEATURE2_ARCH_3_00	= 0x00800000  // ISA 3.0 (POWER9)
+)
+
+var hwcap2 uint32
+
+// Function for runtime capability checks.
+// supports = feature mask (see __PPC_FEATURE2 constants above)
+func checkppc64lesupports(supports uint32) bool {
+	if (hwcap2 & supports) == 0 {
+		return false
+	} else {
+		return true
+	}
+}
+
+
+func archauxv(tag, val uintptr) {
+	switch tag {
+	case _AT_HWCAP2:
+		hwcap2 = uint32(val)
+	}
+}