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| author | Keith Randall <khr@golang.org> | 2025-01-10 17:33:26 -0800 |
|---|---|---|
| committer | Keith Randall <khr@golang.org> | 2025-01-12 22:49:39 -0800 |
| commit | 44a6f817ea0fbeb3ba4aa398794c4e80dba13b1e (patch) | |
| tree | bf8b97d89a07f0185ab42468d20b2e68887f4986 /src | |
| parent | 19e923182e590ae6568c2c714f20f32512aeb3e3 (diff) | |
| download | go-44a6f817ea0fbeb3ba4aa398794c4e80dba13b1e.tar.xz | |
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 <khr@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>
Diffstat (limited to 'src')
| -rw-r--r-- | src/cmd/compile/internal/ssa/writebarrier.go | 15 |
1 files changed, 15 insertions, 0 deletions
diff --git a/src/cmd/compile/internal/ssa/writebarrier.go b/src/cmd/compile/internal/ssa/writebarrier.go index 1caccb7c18..71acefbf8a 100644 --- a/src/cmd/compile/internal/ssa/writebarrier.go +++ b/src/cmd/compile/internal/ssa/writebarrier.go @@ -252,6 +252,7 @@ func writebarrier(f *Func) { var start, end int var nonPtrStores int values := b.Values + hasMove := false FindSeq: for i := len(values) - 1; i >= 0; i-- { w := values[i] @@ -263,6 +264,9 @@ func writebarrier(f *Func) { end = i + 1 } nonPtrStores = 0 + if w.Op == OpMoveWB { + hasMove = true + } case OpVarDef, OpVarLive: continue case OpStore: @@ -273,6 +277,17 @@ func writebarrier(f *Func) { if nonPtrStores > 2 { break FindSeq } + if hasMove { + // We need to ensure that this store happens + // before we issue a wbMove, as the wbMove might + // use the result of this store as its source. + // Even though this store is not write-barrier + // eligible, it might nevertheless be the store + // of a pointer to the stack, which is then the + // source of the move. + // See issue 71228. + break FindSeq + } default: if last == nil { continue |