[dev.ssa] cmd/compile: make "*Value".String more robust

Change-Id: I4ae38440a33574421c9e3e350701e86e8a224b92
Reviewed-on: https://go-review.googlesource.com/13842
Reviewed-by: Todd Neal <todd@tneal.org>
Reviewed-by: Keith Randall <khr@golang.org>

diff --git a/src/cmd/compile/internal/ssa/value.go b/src/cmd/compile/internal/ssa/value.go
index 286edc0cdae4dc4580ed75da3fb519a3b1ab551d..04ea17cce914823a0c2ea7aa6591da58f69a1d87 100644 (file)
--- a/src/cmd/compile/internal/ssa/value.go
+++ b/src/cmd/compile/internal/ssa/value.go
@@ -48,6 +48,9 @@ type Value struct {
 
 // short form print.  Just v#.
 func (v *Value) String() string {
+       if v == nil {
+               return "nil" // should never happen, but not panicking helps with debugging
+       }
        return fmt.Sprintf("v%d", v.ID)
 }