1 files changed, 48 insertions, 0 deletions
diff --git a/libgo/go/runtime/lfstack_64bit.go b/libgo/go/runtime/lfstack_64bit.go
new file mode 100644
index 0000000000..213efb1070
--- /dev/null
+++ b/libgo/go/runtime/lfstack_64bit.go
@@ -0,0 +1,48 @@
+// 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 amd64 arm64 mips64 mips64le ppc64 ppc64le s390x arm64be alpha mipsn64 sparc64
+
+package runtime
+
+import "unsafe"
+
+const (
+	// addrBits is the number of bits needed to represent a virtual address.
+	//
+	// In Linux the user address space for each architecture is limited as
+	// follows (taken from the processor.h file for the architecture):
+	//
+	// Architecture  Name              Maximum Value (exclusive)
+	// ---------------------------------------------------------------------
+	// arm64         TASK_SIZE_64      Depends on configuration.
+	// ppc64{,le}    TASK_SIZE_USER64  0x400000000000UL (46 bit addresses)
+	// mips64{,le}   TASK_SIZE64       0x010000000000UL (40 bit addresses)
+	// s390x         TASK_SIZE         0x020000000000UL (41 bit addresses)
+	//
+	// These values may increase over time.
+	//
+	// On AMD64, virtual addresses are 48-bit numbers sign extended to 64.
+	// We shift the address left 16 to eliminate the sign extended part and make
+	// room in the bottom for the count.
+	addrBits = 48
+
+	// In addition to the 16 bits taken from the top, we can take 3 from the
+	// bottom, because node must be pointer-aligned, giving a total of 19 bits
+	// of count.
+	cntBits = 64 - addrBits + 3
+)
+
+func lfstackPack(node *lfnode, cnt uintptr) uint64 {
+	return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1))
+}
+
+func lfstackUnpack(val uint64) *lfnode {
+	if GOARCH == "amd64" || GOOS == "solaris" {
+		// amd64 or Solaris systems can place the stack above the VA hole, so we need to sign extend
+		// val before unpacking.
+		return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> cntBits << 3)))
+	}
+	return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
+}