[dev.ssa] cmd/compile/internal/ssa: fix defer in functions with no return
The after-defer test jumps to a deferreturn site. Some functions
(those with infinite loops) have no deferreturn site. Add one
so we have one to jump to.
Change-Id: I505e7f3f888f5e7d03ca49a3477b41cf1f78eb8a
Reviewed-on: https://go-review.googlesource.com/14349
Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
diff --git a/src/cmd/compile/internal/gc/ssa.go b/src/cmd/compile/internal/gc/ssa.go
index 098a1e1..70990bb 100644
--- a/src/cmd/compile/internal/gc/ssa.go
+++ b/src/cmd/compile/internal/gc/ssa.go
@@ -2621,6 +2621,12 @@
for _, br := range s.branches {
br.p.To.Val = s.bstart[br.b.ID]
}
+ if s.deferBranches != nil && s.deferTarget == nil {
+ // This can happen when the function has a defer but
+ // no return (because it has an infinite loop).
+ s.deferReturn()
+ Prog(obj.ARET)
+ }
for _, p := range s.deferBranches {
p.To.Val = s.deferTarget
}
@@ -3463,20 +3469,7 @@
case ssa.BlockExit:
case ssa.BlockRet:
if Hasdefer != 0 {
- // Deferred calls will appear to be returning to
- // the CALL deferreturn(SB) that we are about to emit.
- // However, the stack trace code will show the line
- // of the instruction byte before the return PC.
- // To avoid that being an unrelated instruction,
- // insert an actual hardware NOP that will have the right line number.
- // This is different from obj.ANOP, which is a virtual no-op
- // that doesn't make it into the instruction stream.
- s.deferTarget = Pc
- Thearch.Ginsnop()
- p := Prog(obj.ACALL)
- p.To.Type = obj.TYPE_MEM
- p.To.Name = obj.NAME_EXTERN
- p.To.Sym = Linksym(Deferreturn.Sym)
+ s.deferReturn()
}
Prog(obj.ARET)
case ssa.BlockCall:
@@ -3537,6 +3530,23 @@
}
}
+func (s *genState) deferReturn() {
+ // Deferred calls will appear to be returning to
+ // the CALL deferreturn(SB) that we are about to emit.
+ // However, the stack trace code will show the line
+ // of the instruction byte before the return PC.
+ // To avoid that being an unrelated instruction,
+ // insert an actual hardware NOP that will have the right line number.
+ // This is different from obj.ANOP, which is a virtual no-op
+ // that doesn't make it into the instruction stream.
+ s.deferTarget = Pc
+ Thearch.Ginsnop()
+ p := Prog(obj.ACALL)
+ p.To.Type = obj.TYPE_MEM
+ p.To.Name = obj.NAME_EXTERN
+ p.To.Sym = Linksym(Deferreturn.Sym)
+}
+
// addAux adds the offset in the aux fields (AuxInt and Aux) of v to a.
func addAux(a *obj.Addr, v *ssa.Value) {
if a.Type != obj.TYPE_MEM {
