cmd/compile: always use StackMapDontCare as register map index when reg map is not...

When go115ReduceLiveness is true (so we don't emit actual
register maps), use StackMapDontCare consistently for the
register map index, so RegMapValid is always false.

This fixes a compiler crash when doing -live=2 debug print.

Fixes #39251.

Change-Id: Ice087af491fa69c413f8ee59f923b72d592c0643
Reviewed-on: https://go-review.googlesource.com/c/go/+/235418
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>

diff --git a/src/cmd/compile/internal/gc/plive.go b/src/cmd/compile/internal/gc/plive.go
index a4c051bda6defa66f74734c35ab9fa371a3d0d87..e2de6286a03ff7378dd44363c52607c0b211d727 100644 (file)
--- a/src/cmd/compile/internal/gc/plive.go
+++ b/src/cmd/compile/internal/gc/plive.go
@@ -1249,7 +1249,7 @@ func (lv *Liveness) compact(b *ssa.Block) {
                if go115ReduceLiveness {
                        hasStackMap := lv.hasStackMap(v)
                        isUnsafePoint := lv.allUnsafe || lv.unsafePoints.Get(int32(v.ID))
-                       idx := LivenessIndex{StackMapDontCare, 0, isUnsafePoint}
+                       idx := LivenessIndex{StackMapDontCare, StackMapDontCare, isUnsafePoint}
                        if hasStackMap {
                                idx.stackMapIndex = lv.stackMapSet.add(lv.livevars[pos].vars)
                                pos++