From 44a6f817ea0fbeb3ba4aa398794c4e80dba13b1e Mon Sep 17 00:00:00 2001 From: Keith Randall Date: Fri, 10 Jan 2025 17:33:26 -0800 Subject: cmd/compile: fix write barrier coalescing We can't coalesce a non-WB store with a subsequent Move, as the result of the store might be the source of the move. There's a simple codegen test. Not sure how we might do a real test, as all the repro's I've come up with are very expensive and unreliable. Fixes #71228 Change-Id: If18bf181a266b9b90964e2591cd2e61a7168371c Reviewed-on: https://go-review.googlesource.com/c/go/+/642197 Reviewed-by: Keith Randall LUCI-TryBot-Result: Go LUCI Reviewed-by: David Chase --- test/codegen/writebarrier.go | 25 +++++++++++++++++++++++++ 1 file changed, 25 insertions(+) (limited to 'test/codegen') diff --git a/test/codegen/writebarrier.go b/test/codegen/writebarrier.go index e125973e7c..e2b1399399 100644 --- a/test/codegen/writebarrier.go +++ b/test/codegen/writebarrier.go @@ -63,3 +63,28 @@ func trickyWriteNil(p *int, q **int) { *q = p } } + +type S struct { + a, b string + c *int +} + +var g1, g2 *int + +func issue71228(dst *S, ptr *int) { + // Make sure that the non-write-barrier write. + // "sp.c = ptr" happens before the large write + // barrier "*dst = *sp". We approximate testing + // that by ensuring that two global variable write + // barriers aren't combined. + _ = *dst + var s S + sp := &s + //amd64:`.*runtime[.]gcWriteBarrier1` + g1 = nil + sp.c = ptr // outside of any write barrier + //amd64:`.*runtime[.]gcWriteBarrier1` + g2 = nil + //amd64:`.*runtime[.]wbMove` + *dst = *sp +} -- cgit v1.3