753da7ae9d
cmd/compile: fix findIndVar so it does not match disjointed loop headers Signed-off-by: EulerOSWander <314264452@qq.com> (cherry picked from commit 9d7cc4fab07218f896e6a9265a231f5108d53135)
92 lines
3.2 KiB
Diff
92 lines
3.2 KiB
Diff
From 4ef68a16e21a2e63f2f6bdc498fe34c9ca994011 Mon Sep 17 00:00:00 2001
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From: Jorropo <jorropo.pgm@gmail.com>
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Date: Sun, 5 Nov 2023 22:40:01 +0100
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Subject: [PATCH 05/20] [release-branch.go1.21] cmd/compile: fix findIndVar so
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it does not match disjointed loop headers
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Fix #63984
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Conflict:NA
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Reference:https://go-review.googlesource.com/c/go/+/539977
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parseIndVar, prove and maybe more are on the assumption that the loop header
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is a single block. This can be wrong, ensure we don't match theses cases we
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don't know how to handle.
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In the future we could update them so that they know how to handle such cases
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but theses cases seems rare so I don't think the value would be really high.
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We could also run a loop canonicalization pass first which could handle this.
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The repro case looks weird because I massaged it so it would crash with the
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previous compiler.
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Change-Id: I4aa8afae9e90a17fa1085832250fc1139c97faa6
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Reviewed-on: https://go-review.googlesource.com/c/go/+/539977
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Reviewed-by: Heschi Kreinick <heschi@google.com>
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Reviewed-by: Keith Randall <khr@golang.org>
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Reviewed-by: Keith Randall <khr@google.com>
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LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
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(cherry picked from commit 8b4e1259d0e82c8fe38a1456f997a4e9d63573a2)
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Reviewed-on: https://go-review.googlesource.com/c/go/+/540535
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Reviewed-by: Jorropo <jorropo.pgm@gmail.com>
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Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
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Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
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Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
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Auto-Submit: Dmitri Shuralyov <dmitshur@google.com>
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Reviewed-by: Michael Knyszek <mknyszek@google.com>
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---
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src/cmd/compile/internal/ssa/loopbce.go | 7 +++++++
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test/fixedbugs/issue63955.go | 22 ++++++++++++++++++++++
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2 files changed, 29 insertions(+)
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create mode 100644 test/fixedbugs/issue63955.go
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diff --git a/src/cmd/compile/internal/ssa/loopbce.go b/src/cmd/compile/internal/ssa/loopbce.go
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index b7dfaa33e3bf..7f432e61ba50 100644
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--- a/src/cmd/compile/internal/ssa/loopbce.go
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+++ b/src/cmd/compile/internal/ssa/loopbce.go
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@@ -127,6 +127,13 @@ func findIndVar(f *Func) []indVar {
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less = false
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}
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+ if ind.Block != b {
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+ // TODO: Could be extended to include disjointed loop headers.
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+ // I don't think this is causing missed optimizations in real world code often.
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+ // See https://go.dev/issue/63955
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+ continue
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+ }
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+
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// Expect the increment to be a nonzero constant.
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if !inc.isGenericIntConst() {
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continue
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diff --git a/test/fixedbugs/issue63955.go b/test/fixedbugs/issue63955.go
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new file mode 100644
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index 000000000000..258e874220f0
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--- /dev/null
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+++ b/test/fixedbugs/issue63955.go
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@@ -0,0 +1,22 @@
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+// compile
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+
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+// Copyright 2023 The Go Authors. All rights reserved.
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+// Use of this source code is governed by a BSD-style
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+// license that can be found in the LICENSE file.
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+
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+package j
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+
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+func f(try func() int, shouldInc func() bool, N func(int) int) {
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+ var n int
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+loop: // we want to have 3 preds here, the function entry and both gotos
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+ if v := try(); v == 42 || v == 1337 { // the two || are to trick findIndVar
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+ if n < 30 { // this aims to be the matched block
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+ if shouldInc() {
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+ n++
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+ goto loop
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+ }
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+ n = N(n) // try to prevent some block joining
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+ goto loop
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+ }
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+ }
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+}
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--
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2.33.0
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