runtime: remove unused return value from lfstackUnpack

None of the two places that call lfstackUnpack use the second argument.
This simplifies a followup CL that merges the lfstack{Pack,Unpack}
implementations.

Change-Id: I3c93f6259da99e113d94f8c8027584da79c1ac2c
Reviewed-on: https://go-review.googlesource.com/21595
Run-TryBot: Dave Cheney <dave@cheney.net>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/runtime/lfstack.go

@@ -15,7 +15,7 @@ import (
 func lfstackpush(head *uint64, node *lfnode) {
 	node.pushcnt++
 	new := lfstackPack(node, node.pushcnt)
-	if node1, _ := lfstackUnpack(new); node1 != node {
+	if node1 := lfstackUnpack(new); node1 != node {
 		print("runtime: lfstackpush invalid packing: node=", node, " cnt=", hex(node.pushcnt), " packed=", hex(new), " -> node=", node1, "\n")
 		throw("lfstackpush")
 	}
@@ -34,7 +34,7 @@ func lfstackpop(head *uint64) unsafe.Pointer {
 		if old == 0 {
 			return nil
 		}
-		node, _ := lfstackUnpack(old)
+		node := lfstackUnpack(old)
 		next := atomic.Load64(&node.next)
 		if atomic.Cas64(head, old, next) {
 			return unsafe.Pointer(node)

src/runtime/lfstack_32bit.go

@@ -14,8 +14,6 @@ func lfstackPack(node *lfnode, cnt uintptr) uint64 {
 	return uint64(uintptr(unsafe.Pointer(node)))<<32 | uint64(cnt)
 }
 
-func lfstackUnpack(val uint64) (node *lfnode, cnt uintptr) {
-	node = (*lfnode)(unsafe.Pointer(uintptr(val >> 32)))
-	cnt = uintptr(val)
-	return
+func lfstackUnpack(val uint64) *lfnode {
+	return (*lfnode)(unsafe.Pointer(uintptr(val >> 32)))
 }

src/runtime/lfstack_64bit.go

@@ -28,8 +28,6 @@ func lfstackPack(node *lfnode, cnt uintptr) uint64 {
 	return uint64(uintptr(unsafe.Pointer(node)))<<(64-addrBits) | uint64(cnt&(1<<cntBits-1))
 }
 
-func lfstackUnpack(val uint64) (node *lfnode, cnt uintptr) {
-	node = (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
-	cnt = uintptr(val & (1<<cntBits - 1))
-	return
+func lfstackUnpack(val uint64) *lfnode {
+	return (*lfnode)(unsafe.Pointer(uintptr(val >> cntBits << 3)))
 }

src/runtime/lfstack_amd64.go

@@ -17,8 +17,6 @@ func lfstackPack(node *lfnode, cnt uintptr) uint64 {
 	return uint64(uintptr(unsafe.Pointer(node)))<<16 | uint64(cnt&(1<<19-1))
 }
 
-func lfstackUnpack(val uint64) (node *lfnode, cnt uintptr) {
-	node = (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> 19 << 3)))
-	cnt = uintptr(val & (1<<19 - 1))
-	return
+func lfstackUnpack(val uint64) *lfnode {
+	return (*lfnode)(unsafe.Pointer(uintptr(int64(val) >> 19 << 3)))
 }