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-rw-r--r--llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp11
-rw-r--r--llvm/test/Transforms/InstCombine/pr44245.ll192
2 files changed, 200 insertions, 3 deletions
diff --git a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
index f6c7bb5d447..71b7f279e5f 100644
--- a/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/llvm/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -2319,9 +2319,14 @@ Instruction *InstCombiner::optimizeBitCastFromPhi(CastInst &CI, PHINode *PN) {
if (auto *C = dyn_cast<Constant>(V)) {
NewV = ConstantExpr::getBitCast(C, DestTy);
} else if (auto *LI = dyn_cast<LoadInst>(V)) {
- Builder.SetInsertPoint(LI->getNextNode());
- NewV = Builder.CreateBitCast(LI, DestTy);
- Worklist.Add(LI);
+ // Explicitly perform load combine to make sure no opposing transform
+ // can remove the bitcast in the meantime and trigger an infinite loop.
+ Builder.SetInsertPoint(LI);
+ NewV = combineLoadToNewType(*LI, DestTy);
+ // Remove the old load and its use in the old phi, which itself becomes
+ // dead once the whole transform finishes.
+ replaceInstUsesWith(*LI, UndefValue::get(LI->getType()));
+ eraseInstFromFunction(*LI);
} else if (auto *BCI = dyn_cast<BitCastInst>(V)) {
NewV = BCI->getOperand(0);
} else if (auto *PrevPN = dyn_cast<PHINode>(V)) {
diff --git a/llvm/test/Transforms/InstCombine/pr44245.ll b/llvm/test/Transforms/InstCombine/pr44245.ll
new file mode 100644
index 00000000000..f75e26e87ad
--- /dev/null
+++ b/llvm/test/Transforms/InstCombine/pr44245.ll
@@ -0,0 +1,192 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py
+; RUN: opt -S -instcombine -instcombine-infinite-loop-threshold=2 < %s | FileCheck %s
+
+; This used to cause on infinite instcombine loop.
+
+define void @test(i1 %c) {
+; CHECK-LABEL: @test(
+; CHECK-NEXT: bb16:
+; CHECK-NEXT: br i1 [[C:%.*]], label [[BB17:%.*]], label [[BB24:%.*]]
+; CHECK: bb17:
+; CHECK-NEXT: [[TMP0:%.*]] = phi i8* [ [[TMP1:%.*]], [[BB47:%.*]] ], [ undef, [[BB16:%.*]] ]
+; CHECK-NEXT: store i8* [[TMP0]], i8** undef, align 8
+; CHECK-NEXT: ret void
+; CHECK: bb24:
+; CHECK-NEXT: br i1 [[C]], label [[BB44:%.*]], label [[BB49:%.*]]
+; CHECK: bb44:
+; CHECK-NEXT: [[TMP467:%.*]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb47:
+; CHECK-NEXT: [[TMP1]] = phi i8* [ [[TMP2:%.*]], [[BB150:%.*]] ], [ [[TMP1221:%.*]], [[BB119:%.*]] ], [ [[TMP1032:%.*]], [[BB101:%.*]] ], [ [[TMP933:%.*]], [[BB91:%.*]] ], [ [[TMP834:%.*]], [[BB81:%.*]] ], [ [[TMP705:%.*]], [[BB67:%.*]] ], [ [[TMP586:%.*]], [[BB56:%.*]] ], [ [[TMP467]], [[BB44]] ]
+; CHECK-NEXT: br label [[BB17]]
+; CHECK: bb49:
+; CHECK-NEXT: br i1 [[C]], label [[BB56]], label [[BB59:%.*]]
+; CHECK: bb56:
+; CHECK-NEXT: [[TMP586]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb59:
+; CHECK-NEXT: br i1 [[C]], label [[BB67]], label [[BB71:%.*]]
+; CHECK: bb67:
+; CHECK-NEXT: [[TMP705]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb71:
+; CHECK-NEXT: br i1 [[C]], label [[BB81]], label [[BB84:%.*]]
+; CHECK: bb81:
+; CHECK-NEXT: [[TMP834]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb84:
+; CHECK-NEXT: br i1 [[C]], label [[BB91]], label [[BB94:%.*]]
+; CHECK: bb91:
+; CHECK-NEXT: [[TMP933]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb94:
+; CHECK-NEXT: br i1 [[C]], label [[BB101]], label [[BB104:%.*]]
+; CHECK: bb101:
+; CHECK-NEXT: [[TMP1032]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb104:
+; CHECK-NEXT: br i1 [[C]], label [[BB119]], label [[BB123:%.*]]
+; CHECK: bb119:
+; CHECK-NEXT: [[TMP1221]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb123:
+; CHECK-NEXT: br i1 [[C]], label [[BB147:%.*]], label [[BB152:%.*]]
+; CHECK: bb147:
+; CHECK-NEXT: [[TMP1499:%.*]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: br label [[BB150]]
+; CHECK: bb150:
+; CHECK-NEXT: [[TMP2]] = phi i8* [ [[TMP1848:%.*]], [[BB152]] ], [ [[TMP1499]], [[BB147]] ]
+; CHECK-NEXT: br label [[BB47]]
+; CHECK: bb152:
+; CHECK-NEXT: [[TMP1848]] = load i8*, i8** inttoptr (i64 16 to i8**), align 16
+; CHECK-NEXT: call void undef()
+; CHECK-NEXT: br label [[BB150]]
+;
+bb16: ; preds = %bb
+ br i1 %c, label %bb17, label %bb24
+
+bb17: ; preds = %bb47, %bb17
+ %0 = phi i8* [ %1, %bb47 ], [ undef, %bb16 ]
+ store i8* %0, i8** undef, align 8
+ ret void
+
+bb24: ; preds = %bb24
+ br i1 %c, label %bb44, label %bb49
+
+bb44: ; preds = %bb43
+ %tmp46 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb47: ; preds = %bb150, %bb119, %bb101, %bb91, %bb81, %bb67, %bb56, %bb44
+ %.in1 = phi i64* [ %.in, %bb150 ], [ %tmp122, %bb119 ], [ %tmp103, %bb101 ], [ %tmp93, %bb91 ], [ %tmp83, %bb81 ], [ %tmp70, %bb67 ], [ %tmp58, %bb56 ], [ %tmp46, %bb44 ]
+ %1 = bitcast i64* %.in1 to i8*
+ br label %bb17
+
+bb49: ; preds = %bb49
+ br i1 %c, label %bb56, label %bb59
+
+bb56: ; preds = %bb55
+ %tmp58 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb59: ; preds = %bb59
+ br i1 %c, label %bb67, label %bb71
+
+bb67: ; preds = %bb66
+ %tmp70 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb71: ; preds = %bb71
+ br i1 %c, label %bb81, label %bb84
+
+bb81: ; preds = %bb80
+ %tmp83 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb84: ; preds = %bb84
+ br i1 %c, label %bb91, label %bb94
+
+bb91: ; preds = %bb90
+ %tmp93 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb94: ; preds = %bb94
+ br i1 %c, label %bb101, label %bb104
+
+bb101: ; preds = %bb100
+ %tmp103 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb104: ; preds = %bb104
+ br i1 %c, label %bb119, label %bb123
+
+bb119: ; preds = %bb118
+ %tmp122 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb47
+
+bb123: ; preds = %bb123
+ br i1 %c, label %bb147, label %bb152
+
+bb147: ; preds = %bb146
+ %tmp149 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ br label %bb150
+
+bb150: ; preds = %bb152, %bb147
+ %.in = phi i64* [ %tmp184, %bb152 ], [ %tmp149, %bb147 ]
+ br label %bb47
+
+bb152: ; preds = %bb146
+ %tmp184 = load i64*, i64** inttoptr (i64 16 to i64**), align 16
+ call void undef()
+ br label %bb150
+}
+
+; This used to cause an instcombine loop when the problem above was
+; addressed in a non-robust fashion.
+
+%type_1 = type {}
+%type_2 = type {}
+%type_3 = type {}
+
+define void @test_2(i1 %c) local_unnamed_addr {
+; CHECK-LABEL: @test_2(
+; CHECK-NEXT: entry:
+; CHECK-NEXT: br label [[WHILE_COND:%.*]]
+; CHECK: while.cond:
+; CHECK-NEXT: br label [[FOR_COND:%.*]]
+; CHECK: for.cond:
+; CHECK-NEXT: br i1 [[C:%.*]], label [[COND_TRUE133:%.*]], label [[COND_FALSE138:%.*]]
+; CHECK: cond.true133:
+; CHECK-NEXT: store %type_3* undef, %type_3** null, align 536870912
+; CHECK-NEXT: br label [[COND_END144:%.*]]
+; CHECK: cond.false138:
+; CHECK-NEXT: store %type_3* undef, %type_3** null, align 536870912
+; CHECK-NEXT: br label [[COND_END144]]
+; CHECK: cond.end144:
+; CHECK-NEXT: br label [[WHILE_COND]]
+;
+entry:
+ br label %while.cond
+
+while.cond: ; preds = %cond.end144, %entry
+ %link.0 = phi %type_2* [ undef, %entry ], [ %cond145, %cond.end144 ]
+ %os115 = bitcast %type_2* %link.0 to %type_3*
+ %ou116 = getelementptr inbounds %type_3, %type_3* %os115, i32 0
+ %os1117 = bitcast %type_3* %ou116 to %type_1*
+ br label %for.cond
+
+for.cond: ; preds = %while.cond
+ br i1 %c, label %cond.true133, label %cond.false138
+
+cond.true133: ; preds = %sw.epilog
+ %0 = load %type_2*, %type_2** undef, align 8
+ br label %cond.end144
+
+cond.false138: ; preds = %sw.epilog
+ %1 = load %type_2*, %type_2** undef, align 8
+ br label %cond.end144
+
+cond.end144: ; preds = %cond.false138, %cond.true133
+ %cond145 = phi %type_2* [ %0, %cond.true133 ], [ %1, %cond.false138 ]
+ br label %while.cond
+}
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