[dev.cc] runtime: fix lfstack for amd64 addresses in top half of addr space

While we are here, add the linux/power64 version.

LGTM=austin
R=austin
CC=aram, dvyukov, golang-codereviews
https://golang.org/cl/177750043

1 files changed, 26 insertions, 0 deletions

diff --git a/src/runtime/lfstack_linux_power64x.go b/src/runtime/lfstack_linux_power64x.go
new file mode 100644
index 0000000000..7a122bf92c
--- /dev/null
+++ b/src/runtime/lfstack_linux_power64x.go
@@ -0,0 +1,26 @@
+// Copyright 2014 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 power64 power64le
+// +build linux
+
+package runtime
+
+import "unsafe"
+
+// On Power64, Linux limits the user address space to 43 bits.
+// (https://www.kernel.org/doc/ols/2001/ppc64.pdf)
+// In addition to the 21 bits taken from the top, we can take 3 from the
+// bottom, because node must be pointer-aligned, giving a total of 24 bits
+// of count.
+
+func lfstackPack(node *lfnode, cnt uintptr) uint64 {
+	return uint64(uintptr(unsafe.Pointer(node)))<<21 | uint64(cnt&(1<<24-1))
+}
+
+func lfstackUnpack(val uint64) (node *lfnode, cnt uintptr) {
+	node = (*lfnode)(unsafe.Pointer(uintptr(val >> 24 << 3)))
+	cnt = uintptr(val & (1<<24 - 1))
+	return
+}