libgo patch committed: Fix lfstack for AIX

[Ian Lance Taylor]

This patch by Tony Reix fixes the runtime package's lock-free stack
code to work on 64-bit AIX.  Bootstrapped on x86_64-pc-linux-gnu.
Committed to mainline.

Ian

Index: gcc/go/gofrontend/MERGE
===================================================================
--- gcc/go/gofrontend/MERGE     (revision 251188)
+++ gcc/go/gofrontend/MERGE     (working copy)
@@ -1,4 +1,4 @@
-2c4a2bd826e58c8c8c51b9196c8d2c67abc4037e
+db8e3801bf8508656606d6e465c76cdc6e9a9eb7
 
 The first line of this file holds the git revision number of the last
 merge done from the gofrontend repository.
Index: libgo/go/runtime/lfstack_64bit.go
===================================================================
--- libgo/go/runtime/lfstack_64bit.go   (revision 250873)
+++ libgo/go/runtime/lfstack_64bit.go   (working copy)
@@ -43,6 +43,14 @@ const (
        // 52 address bits each (with 64k page size).
        ia64AddrBits = 55
        ia64CntBits  = 64 - ia64AddrBits + 3
+
+       // On AIX, 64-bit addresses are split into 36-bit segment number and 
28-bit
+       // offset in segment.  Segment numbers in the range 
0x070000000-0x07FFFFFFF
+       // and 0x0A0000000-0x0AFFFFFFF(LSA) are available for mmap.
+       // We assume all lfnode addresses are from memory allocated with mmap.
+       // We use one bit to distinguish between the two ranges.
+       aixAddrBits = 57
+       aixCntBits  = 64 - aixAddrBits + 3
 )
 
 func lfstackPack(node *lfnode, cnt uintptr) uint64 {
@@ -54,6 +62,9 @@ func lfstackPack(node *lfnode, cnt uintp
                val := uint64(uintptr(unsafe.Pointer(node)))
                return (val<<(64-ia64AddrBits))&(1<<(64-3)-1) | 
val&^(1<<(64-3)-1) | uint64(cnt&(1<<ia64CntBits-1))
        }
+       if GOARCH == "ppc64" && GOOS == "aix" {
+               return uint64(uintptr(unsafe.Pointer(node)))<<(64-aixAddrBits) 
| uint64(cnt&(1<<aixCntBits-1))
+       }
        return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | 
uint64(cnt&(1<<cntBits-1))
 }
 
@@ -69,5 +80,12 @@ func lfstackUnpack(val uint64) *lfnode {
        if GOARCH == "ia64" {
                return 
(*lfnode)(unsafe.Pointer(uintptr((val>>ia64CntBits<<3)&(1<<(64-3)-1) | 
val&^(1<<(64-3)-1))))
        }
+       if GOARCH == "ppc64" && GOOS == "aix" {
+               if val&(1<<63) != 0 {
+                       return (*lfnode)(unsafe.Pointer(uintptr((val >> 
aixCntBits << 3) | 0x7<<56)))
+               } else {
+                       return (*lfnode)(unsafe.Pointer(uintptr((val >> 
aixCntBits << 3) | 0xa<<56)))
+               }
+       }
        return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
 }