gc: fix complex move bug

R=ken2
CC=golang-dev
https://golang.org/cl/4439044

diff --git a/src/cmd/gc/cplx.c b/src/cmd/gc/cplx.c
index 3ec9fe5a2c6b537222dd9b563333b3f28a4a1184..6eb220db9fd67bff8ff2c246ddf9001276bc93ef 100644 (file)
--- a/src/cmd/gc/cplx.c
+++ b/src/cmd/gc/cplx.c
@@ -21,7 +21,7 @@ void
 complexmove(Node *f, Node *t)
 {
        int ft, tt;
-       Node n1, n2, n3, n4;
+       Node n1, n2, n3, n4, t3, t4;
 
        if(debug['g']) {
                dump("\ncomplexmove-f", f);
@@ -54,8 +54,21 @@ complexmove(Node *f, Node *t)
                subnode(&n1, &n2, f);
                subnode(&n3, &n4, t);
 
-               cgen(&n1, &n3);
-               cgen(&n2, &n4);
+               // Copy fully into registers before doing stores,
+               // in case the source and destination overlap.
+               // Might be picking up a complex128 from one
+               // location on the stack and writing it 8 bytes
+               // (half a complex128) later, in which case the
+               // first write would smash the source for the second read.
+               regalloc(&t3, types[tt+TFLOAT64-TCOMPLEX128], N);
+               regalloc(&t4, types[tt+TFLOAT64-TCOMPLEX128], N);
+               cgen(&n1, &t3);
+               cgen(&n2, &t4);
+
+               cgen(&t3, &n3);
+               cgen(&t4, &n4);
+               regfree(&t3);
+               regfree(&t4);
                break;
        }
 }

diff --git a/test/fixedbugs/bug329.go b/test/fixedbugs/bug329.go
new file mode 100644 (file)
index 0000000..ea379c3
--- /dev/null
+++ b/test/fixedbugs/bug329.go
@@ -0,0 +1,50 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2011 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.
+
+// Test that when moving a complex128 returned by one function
+// into the argument position for another function, the right thing
+// happens, even when the two positions half-overlap.
+
+package main
+
+type Value struct {
+       X interface{}
+       Y int
+}
+
+type Struct struct {
+       X complex128
+}
+
+const magic = 1+2i
+
+func (Value) Complex(x complex128) {
+       if x != magic {
+               println(x)
+               panic("bad complex magic")
+       }
+}
+
+func f(x *byte, y, z int) complex128 {
+       return magic
+}
+
+func (Value) Struct(x Struct) {
+       if x.X != magic {
+               println(x.X)
+               panic("bad struct magic")
+       }
+}
+
+func f1(x *byte, y, z int) Struct {
+       return Struct{magic}
+}
+
+func main() {
+       var v Value
+       v.Struct(f1(nil, 0, 0))  // ok
+       v.Complex(f(nil, 0, 0))  // used to fail
+}