Revert "[StructurizeCFG] Refactor insertConditions. NFC. (#115476)" #136370
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This reverts commit `231e63d8162a1c78a973c6e546bea39d04fefd67` because it was intended to be NFC, but it actually introduces a semantic change. The behavior is not equivalent to the original code. Specifically, the change attempts to make the special case of `Parent` being the only predecessor more explicit by isolating it, and then asserts in the `else` branch that `BB` can't be `Parent`. However, it's still possible for `Preds.size() > 1`, in which case `BB` can be `Parent`, causing the assertion to trigger. Eventually, this introduced a regression (though the related test case wasn't in the repo at the time). To fix it properly, we'd have to reintroduce logic in the `else` block to handle the case where `BB` is `Parent`, which counters the intent of the original refactor. Because of that, I think it's cleaner and more reliable to simply revert the commit. Fixes #126534.
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@llvm/pr-subscribers-llvm-transforms Author: Shilei Tian (shiltian) ChangesThis reverts commit 231e63d because it was Specifically, the change attempts to make the special case of Eventually, this introduced a regression (though the related test case wasn't in Fixes #126534. Full diff: https://github.com/llvm/llvm-project/pull/136370.diff 2 Files Affected:
diff --git a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
index 00c4fcc76e791..eb22b50532695 100644
--- a/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
+++ b/llvm/lib/Transforms/Scalar/StructurizeCFG.cpp
@@ -612,25 +612,28 @@ void StructurizeCFG::insertConditions(bool Loops) {
BasicBlock *SuccTrue = Term->getSuccessor(0);
BasicBlock *SuccFalse = Term->getSuccessor(1);
- BBPredicates &Preds = Loops ? LoopPreds[SuccFalse] : Predicates[SuccTrue];
+ PhiInserter.Initialize(Boolean, "");
+ PhiInserter.AddAvailableValue(Loops ? SuccFalse : Parent, Default);
- if (Preds.size() == 1 && Preds.begin()->first == Parent) {
- auto &PI = Preds.begin()->second;
- Term->setCondition(PI.Pred);
- CondBranchWeights::setMetadata(*Term, PI.Weights);
- } else {
- PhiInserter.Initialize(Boolean, "");
- PhiInserter.AddAvailableValue(Loops ? SuccFalse : Parent, Default);
+ BBPredicates &Preds = Loops ? LoopPreds[SuccFalse] : Predicates[SuccTrue];
- NearestCommonDominator Dominator(DT);
- Dominator.addBlock(Parent);
+ NearestCommonDominator Dominator(DT);
+ Dominator.addBlock(Parent);
- for (auto [BB, PI] : Preds) {
- assert(BB != Parent);
- PhiInserter.AddAvailableValue(BB, PI.Pred);
- Dominator.addAndRememberBlock(BB);
+ PredInfo ParentInfo{nullptr, std::nullopt};
+ for (auto [BB, PI] : Preds) {
+ if (BB == Parent) {
+ ParentInfo = PI;
+ break;
}
+ PhiInserter.AddAvailableValue(BB, PI.Pred);
+ Dominator.addAndRememberBlock(BB);
+ }
+ if (ParentInfo.Pred) {
+ Term->setCondition(ParentInfo.Pred);
+ CondBranchWeights::setMetadata(*Term, ParentInfo.Weights);
+ } else {
if (!Dominator.resultIsRememberedBlock())
PhiInserter.AddAvailableValue(Dominator.result(), Default);
diff --git a/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll b/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll
index 6edc0b883f51e..691f43bdcf948 100644
--- a/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll
+++ b/llvm/test/Transforms/StructurizeCFG/simple-structurizecfg-crash.ll
@@ -1,11 +1,19 @@
-; RUN: opt -S -passes=structurizecfg %s -o -
-; REQUIRES: asserts
-; XFAIL: *
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=structurizecfg %s -o - | FileCheck %s
; Issue tracking: https://github.com/llvm/llvm-project/issues/126534.
-; FIXME: This test is expected to crash. Generate checklines after the crash is fixed.
define void @foo() {
+; CHECK-LABEL: define void @foo() {
+; CHECK-NEXT: [[ENTRY:.*:]]
+; CHECK-NEXT: br label %[[COND_FALSE:.*]]
+; CHECK: [[COND_TRUE:.*]]:
+; CHECK-NEXT: br label %[[COND_END:.*]]
+; CHECK: [[COND_FALSE]]:
+; CHECK-NEXT: br i1 false, label %[[COND_TRUE]], label %[[COND_END]]
+; CHECK: [[COND_END]]:
+; CHECK-NEXT: ret void
+;
entry:
br i1 false, label %cond.true, label %cond.false
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arsenm
approved these changes
Apr 19, 2025
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This reverts commit 231e63d because it was
intended to be NFC, but it actually introduces a semantic change. The behavior
is not equivalent to the original code.
Specifically, the change attempts to make the special case of
Parentbeing theonly predecessor more explicit by isolating it, and then asserts in the
elsebranch that
BBcan't beParent. However, it's still possible forPreds.size() > 1, andBBcan still beParent, causing the assertion totrigger.
Eventually, this introduced a regression (though the related test case wasn't in
the repo at the time). To fix it properly, we'd have to reintroduce logic in the
elseblock to handle the case whereBBisParent, which counters theintent of the original refactor. Because of that, I think it's cleaner to simply
revert the commit.
Fixes #126534.