Index: lib/Passes/PassBuilder.cpp =================================================================== --- lib/Passes/PassBuilder.cpp +++ lib/Passes/PassBuilder.cpp @@ -624,6 +624,10 @@ // And finally clean up LCSSA form before generating code. OptimizePM.addPass(InstSimplifierPass()); + // LoopSink (and other loop passes since the last simplifyCFG) might have + // resulted in single-entry-single-exit or empty blocks. Clean up the CFG. + OptimizePM.addPass(SimplifyCFGPass()); + // Add the core optimizing pipeline. MPM.addPass(createModuleToFunctionPassAdaptor(std::move(OptimizePM))); Index: lib/Transforms/IPO/PassManagerBuilder.cpp =================================================================== --- lib/Transforms/IPO/PassManagerBuilder.cpp +++ lib/Transforms/IPO/PassManagerBuilder.cpp @@ -661,6 +661,11 @@ MPM.add(createLoopSinkPass()); // Get rid of LCSSA nodes. MPM.add(createInstructionSimplifierPass()); + + // LoopSink (and other loop passes since the last simplifyCFG) might have + // resulted in single-entry-single-exit or empty blocks. Clean up the CFG. + MPM.add(createCFGSimplificationPass()); + addExtensionsToPM(EP_OptimizerLast, MPM); } Index: test/Other/new-pm-defaults.ll =================================================================== --- test/Other/new-pm-defaults.ll +++ test/Other/new-pm-defaults.ll @@ -153,6 +153,7 @@ ; CHECK-O-NEXT: Running pass: AlignmentFromAssumptionsPass ; CHECK-O-NEXT: Running pass: LoopSinkPass ; CHECK-O-NEXT: Running pass: InstSimplifierPass +; CHECK-O-NEXT: Running pass: SimplifyCFGPass on foo ; CHECK-O-NEXT: Finished llvm::Function pass manager run. ; CHECK-O-NEXT: Running pass: GlobalDCEPass ; CHECK-O-NEXT: Running pass: ConstantMergePass Index: test/Other/pass-pipelines.ll =================================================================== --- test/Other/pass-pipelines.ll +++ test/Other/pass-pipelines.ll @@ -85,6 +85,7 @@ ; CHECK-O2: FunctionPass Manager ; CHECK-O2: Loop Pass Manager ; CHECK-O2-NEXT: Loop Sink +; CHECK-O2: Simplify the CFG ; CHECK-O2-NOT: Manager ; ; FIXME: There really shouldn't be another pass manager, especially one that Index: test/Other/pr32085.ll =================================================================== --- /dev/null +++ test/Other/pr32085.ll @@ -0,0 +1,55 @@ +; RUN: opt -S -O1 < %s | FileCheck %s + +; Test from LoopSink pass, leaves some single-entry single-exit basic blocks. +; After LoopSink, we get a basic block .exit.loopexit which has one entry and +; one exit, the only instruction is a branch. Make sure it doesn't show up. +; Make sure they disappear at -O1. + +; CHECK-NOT: .exit.loopexit + +@g = global i32 0, align 4 + +define i32 @t1(i32, i32) { + %3 = icmp eq i32 %1, 0 + br i1 %3, label %.exit, label %.preheader + +.preheader: + %invariant = load i32, i32* @g + br label %.b1 + +.b1: + %iv = phi i32 [ %t7, %.b7 ], [ 0, %.preheader ] + %c1 = icmp sgt i32 %iv, %0 + br i1 %c1, label %.b2, label %.b6 + +.b2: + %c2 = icmp sgt i32 %iv, 1 + br i1 %c2, label %.b3, label %.b4 + +.b3: + %t3 = sub nsw i32 %invariant, %iv + br label %.b5 + +.b4: + %t4 = add nsw i32 %invariant, %iv + br label %.b5 + +.b5: + %p5 = phi i32 [ %t3, %.b3 ], [ %t4, %.b4 ] + %t5 = mul nsw i32 %p5, 5 + br label %.b7 + +.b6: + %t6 = add nsw i32 %iv, 100 + br label %.b7 + +.b7: + %p7 = phi i32 [ %t6, %.b6 ], [ %t5, %.b5 ] + %t7 = add nuw nsw i32 %iv, 1 + %c7 = icmp eq i32 %t7, %p7 + br i1 %c7, label %.b1, label %.exit + +.exit: + ret i32 10 +} +