5g: defer vs optimizer bug

Fixes #1924.

R=ken2
CC=golang-dev
https://golang.org/cl/4802063

diff --git a/src/cmd/5g/reg.c b/src/cmd/5g/reg.c
index 77d0a87eb596421caa24bf59404ed2182cd8972f..7bb33b7c2565be9a1ca06f533de3236a1a0135bf 100644 (file)
--- a/src/cmd/5g/reg.c
+++ b/src/cmd/5g/reg.c
@@ -728,13 +728,19 @@ addsplits(void)
 void
 addmove(Reg *r, int bn, int rn, int f)
 {
-       Prog *p, *p1;
+       Prog *p, *p1, *p2;
        Adr *a;
        Var *v;
 
        p1 = mal(sizeof(*p1));
        *p1 = zprog;
        p = r->prog;
+       
+       // If there's a stack fixup coming (after BL newproc or BL deferproc),
+       // delay the load until after the fixup.
+       p2 = p->link;
+       if(p2 && p2->as == AMOVW && p2->from.type == D_CONST && p2->from.reg == REGSP && p2->to.reg == REGSP && p2->to.type == D_REG)
+               p = p2;
 
        p1->link = p->link;
        p->link = p1;

diff --git a/test/fixedbugs/bug364.go b/test/fixedbugs/bug364.go
new file mode 100644 (file)
index 0000000..a174534
--- /dev/null
+++ b/test/fixedbugs/bug364.go
@@ -0,0 +1,25 @@
+package main
+
+import "fmt"
+
+var s string
+
+func accum(args ...interface{}) {
+       s += fmt.Sprintln(args...)
+}
+
+func f(){
+       v := 0.0
+       for i := 0; i < 3; i++ {
+               v += 0.1
+               defer accum(v)
+       }
+}
+
+func main() {
+       f()
+       if s != "0.30000000000000004\n0.2\n0.1\n" {
+               println("BUG: defer")
+               print(s)
+       }
+}