From 97bea970651f0df86e245b2b2596003a174fb5d7 Mon Sep 17 00:00:00 2001 From: Austin Clements <austin@google.com> Date: Tue, 22 May 2018 11:07:43 -0400 Subject: [PATCH] cmd/compile: fix unsafe-point analysis with -N Compiling without optimizations (-N) can result in write barrier blocks that have been optimized away but not actually pruned from the block set. Fix unsafe-point analysis to recognize and ignore these. For #24543. Change-Id: I2ca86fb1a0346214ec71d7d6c17b6a121857b01d Reviewed-on: https://go-review.googlesource.com/114076 Run-TryBot: Austin Clements <austin@google.com> Reviewed-by: David Chase <drchase@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> --- src/cmd/compile/internal/gc/plive.go | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/src/cmd/compile/internal/gc/plive.go b/src/cmd/compile/internal/gc/plive.go index 7a953546dc..f42094a0f5 100644 --- a/src/cmd/compile/internal/gc/plive.go +++ b/src/cmd/compile/internal/gc/plive.go @@ -493,6 +493,12 @@ func (lv *Liveness) markUnsafePoints() { // Mark write barrier unsafe points. for _, wbBlock := range lv.f.WBLoads { + if wbBlock.Kind == ssa.BlockPlain && len(wbBlock.Values) == 0 { + // The write barrier block was optimized away + // but we haven't done dead block elimination. + // (This can happen in -N mode.) + continue + } // Check that we have the expected diamond shape. if len(wbBlock.Succs) != 2 { lv.f.Fatalf("expected branch at write barrier block %v", wbBlock) -- 2.30.9