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[FlattenCFG] Fix the miscompilation where phi nodes exist in the merge point (#81987)
When there are phi nodes in the merge point of the if-region, we cannot do the merge. Alive2: https://alive2.llvm.org/ce/z/DbgEan Fixes #70900. (cherry picked from commit f920b746ea818f1d21f317116cbb105e3e85979a)
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@ -407,6 +407,10 @@ bool FlattenCFGOpt::CompareIfRegionBlock(BasicBlock *Block1, BasicBlock *Block2,
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/// form, by inverting the condition and the branch successors. The same
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/// approach goes for the opposite case.
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bool FlattenCFGOpt::MergeIfRegion(BasicBlock *BB, IRBuilder<> &Builder) {
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// We cannot merge the if-region if the merge point has phi nodes.
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if (isa<PHINode>(BB->front()))
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return false;
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BasicBlock *IfTrue2, *IfFalse2;
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BranchInst *DomBI2 = GetIfCondition(BB, IfTrue2, IfFalse2);
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if (!DomBI2)
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@ -493,16 +497,6 @@ bool FlattenCFGOpt::MergeIfRegion(BasicBlock *BB, IRBuilder<> &Builder) {
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PBI->replaceUsesOfWith(PBI->getCondition(), NC);
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Builder.SetInsertPoint(SaveInsertBB, SaveInsertPt);
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// Handle PHI node to replace its predecessors to FirstEntryBlock.
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for (BasicBlock *Succ : successors(PBI)) {
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for (PHINode &Phi : Succ->phis()) {
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for (unsigned i = 0, e = Phi.getNumIncomingValues(); i != e; ++i) {
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if (Phi.getIncomingBlock(i) == SecondEntryBlock)
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Phi.setIncomingBlock(i, FirstEntryBlock);
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}
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}
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}
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// Remove IfTrue1
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if (IfTrue1 != FirstEntryBlock) {
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IfTrue1->dropAllReferences();
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@ -77,13 +77,16 @@ define void @test_not_crash3(i32 %a) #0 {
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; CHECK-SAME: (i32 [[A:%.*]]) {
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; CHECK-NEXT: entry:
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; CHECK-NEXT: [[A_EQ_0:%.*]] = icmp eq i32 [[A]], 0
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; CHECK-NEXT: br i1 [[A_EQ_0]], label [[BB0:%.*]], label [[BB1:%.*]]
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; CHECK: bb0:
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; CHECK-NEXT: br label [[BB1]]
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; CHECK: bb1:
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; CHECK-NEXT: [[A_EQ_1:%.*]] = icmp eq i32 [[A]], 1
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; CHECK-NEXT: [[TMP0:%.*]] = or i1 [[A_EQ_0]], [[A_EQ_1]]
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; CHECK-NEXT: br i1 [[TMP0]], label [[BB2:%.*]], label [[BB3:%.*]]
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; CHECK-NEXT: br i1 [[A_EQ_1]], label [[BB2:%.*]], label [[BB3:%.*]]
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; CHECK: bb2:
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; CHECK-NEXT: br label [[BB3]]
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; CHECK: bb3:
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; CHECK-NEXT: [[CHECK_BADREF:%.*]] = phi i32 [ 17, [[ENTRY:%.*]] ], [ 11, [[BB2]] ]
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; CHECK-NEXT: [[CHECK_BADREF:%.*]] = phi i32 [ 17, [[BB1]] ], [ 11, [[BB2]] ]
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; CHECK-NEXT: ret void
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;
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entry:
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@ -278,9 +281,9 @@ define i1 @test_cond_multi_use(i32 %x, i32 %y, i32 %z) {
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; CHECK-NEXT: entry.x:
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; CHECK-NEXT: [[CMP_X:%.*]] = icmp ne i32 [[X]], 0
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; CHECK-NEXT: [[CMP_Y:%.*]] = icmp eq i32 [[Y]], 0
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; CHECK-NEXT: [[TMP0:%.*]] = xor i1 [[CMP_Y]], true
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; CHECK-NEXT: [[TMP1:%.*]] = or i1 [[CMP_X]], [[TMP0]]
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; CHECK-NEXT: br i1 [[TMP1]], label [[IF_THEN_Y:%.*]], label [[EXIT:%.*]]
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; CHECK-NEXT: [[CMP_Y_NOT:%.*]] = xor i1 [[CMP_Y]], true
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; CHECK-NEXT: [[TMP0:%.*]] = or i1 [[CMP_X]], [[CMP_Y_NOT]]
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; CHECK-NEXT: br i1 [[TMP0]], label [[IF_THEN_Y:%.*]], label [[EXIT:%.*]]
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; CHECK: if.then.y:
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; CHECK-NEXT: store i32 [[Z]], ptr @g, align 4
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; CHECK-NEXT: br label [[EXIT]]
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