diff --git a/llvm/lib/Transforms/Scalar/LoopFuse.cpp b/llvm/lib/Transforms/Scalar/LoopFuse.cpp --- a/llvm/lib/Transforms/Scalar/LoopFuse.cpp +++ b/llvm/lib/Transforms/Scalar/LoopFuse.cpp @@ -99,6 +99,8 @@ STATISTIC(NonEmptyGuardBlock, "Candidate has a non-empty guard block with " "instructions that cannot be moved"); STATISTIC(NotRotated, "Candidate is not rotated"); +STATISTIC(OnlySecondCandidateIsGuarded, + "The second candidate is guarded while the first one is not"); enum FusionDependenceAnalysisChoice { FUSION_DEPENDENCE_ANALYSIS_SCEV, @@ -891,6 +893,14 @@ continue; } + if (!FC0->GuardBranch && FC1->GuardBranch) { + LLVM_DEBUG(dbgs() << "The second candidate is guarded while the " + "first one is not. Not fusing.\n"); + reportLoopFusion( + *FC0, *FC1, OnlySecondCandidateIsGuarded); + continue; + } + // Ensure that FC0 and FC1 have identical guards. // If one (or both) are not guarded, this check is not necessary. if (FC0->GuardBranch && FC1->GuardBranch && diff --git a/llvm/test/Transforms/LoopFusion/pr48060.ll b/llvm/test/Transforms/LoopFusion/pr48060.ll new file mode 100644 --- /dev/null +++ b/llvm/test/Transforms/LoopFusion/pr48060.ll @@ -0,0 +1,69 @@ +; NOTE: Assertions have been autogenerated by utils/update_test_checks.py +; RUN: opt -S -loop-fusion < %s | FileCheck %s +; RUN: opt -S -loop-fusion -pass-remarks-output=%t < %s +; RUN: FileCheck --input-file=%t %s --check-prefix REMARKS + +define dso_local void @pr48060(i1 %cond) { +; CHECK-LABEL: @pr48060( +; CHECK-NEXT: entry: +; CHECK-NEXT: br label [[FOR_1_PH:%.*]] +; CHECK: for.1.ph: +; CHECK-NEXT: br label [[FOR_1:%.*]] +; CHECK: for.1: +; CHECK-NEXT: [[I:%.*]] = phi i32 [ 0, [[FOR_1_PH]] ], [ [[I_NEXT:%.*]], [[FOR_1]] ] +; CHECK-NEXT: [[I_NEXT]] = add i32 [[I]], 1 +; CHECK-NEXT: [[COND_1:%.*]] = icmp eq i32 [[I_NEXT]], 10 +; CHECK-NEXT: br i1 [[COND_1]], label [[FOR_1_EXIT:%.*]], label [[FOR_1]] +; CHECK: for.1.exit: +; CHECK-NEXT: br i1 [[COND:%.*]], label [[END:%.*]], label [[FOR_2_PH:%.*]] +; CHECK: for.2.ph: +; CHECK-NEXT: br label [[FOR_2:%.*]] +; CHECK: for.2: +; CHECK-NEXT: [[J:%.*]] = phi i32 [ 0, [[FOR_2_PH]] ], [ [[J_NEXT:%.*]], [[FOR_2]] ] +; CHECK-NEXT: [[J_NEXT]] = add i32 [[J]], 1 +; CHECK-NEXT: [[COND_2:%.*]] = icmp eq i32 [[J_NEXT]], 10 +; CHECK-NEXT: br i1 [[COND_2]], label [[FOR_2_EXIT:%.*]], label [[FOR_2]] +; CHECK: for.2.exit: +; CHECK-NEXT: br label [[END]] +; CHECK: end: +; CHECK-NEXT: ret void +; + +; REMARKS: --- !Missed +; REMARKS-NEXT: Pass: loop-fusion +; REMARKS-NEXT: Name: OnlySecondCandidateIsGuarded +; REMARKS-NEXT: Function: pr48060 +; REMARKS-NEXT: Args: +; REMARKS: - Cand1: for.1.ph +; REMARKS: - Cand2: for.2.ph +; REMARKS: - String: The second candidate is guarded while the first one is not +entry: + br label %for.1.ph + +for.1.ph: ; preds = %entry + br label %for.1 + +for.1: ; preds = %for.1, %for.1.ph + %i = phi i32 [ 0, %for.1.ph ], [ %i.next, %for.1 ] + %i.next = add i32 %i, 1 + %cond.1 = icmp eq i32 %i.next, 10 + br i1 %cond.1, label %for.1.exit, label %for.1 + +for.1.exit: ; preds = %for.1 + br i1 %cond, label %end, label %for.2.ph + +for.2.ph: ; preds = %for.1.exit + br label %for.2 + +for.2: ; preds = %for.2, %for.2.ph + %j = phi i32 [ 0, %for.2.ph ], [ %j.next, %for.2 ] + %j.next = add i32 %j, 1 + %cond.2 = icmp eq i32 %j.next, 10 + br i1 %cond.2, label %for.2.exit, label %for.2 + +for.2.exit: ; preds = %for.2 + br label %end + +end: ; preds = %for.1.exit, %for.2.exit + ret void +}