cpu: fix build for GOARCH=ppc64{,le} on GOOS!=linux

The current implementation for ppc64{,le} only supports linux (through
HWCaps read from /proc/self/auxv) and fails to build e.g. on
aix/ppc64.

Change-Id: I5e1efe75c781fd08bc7bbe797df88295726ba62b
Reviewed-on: https://go-review.googlesource.com/c/162798
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

cpu/cpu_linux_ppc64x.go

@@ -0,0 +1,33 @@
+// Copyright 2018 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 linux
+// +build ppc64 ppc64le
+
+package cpu
+
+const cacheLineSize = 128
+
+// 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() {
+	// 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)
+}
+
+func isSet(hwc uint, value uint) bool {
+	return hwc&value != 0
+}