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Simplify the CFG after loop pass cleanup.

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Summary:
Otherwise we might end up with some empty basic blocks or
single-entry-single-exit basic blocks.

This fixes PR32085

Reviewers: chandlerc, danielcdh

Subscribers: mehdi_amini, RKSimon, llvm-commits

Differential Revision: https://reviews.llvm.org/D30468

llvm-svn: 301395
This commit is contained in:
Filipe Cabecinhas 2017-04-26 12:02:41 +00:00
parent e1aadb9c34
commit 812c9f7a7a
5 changed files with 67 additions and 0 deletions
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4
lib/Passes/PassBuilder.cpp
View File

@ -624,6 +624,10 @@ PassBuilder::buildPerModuleDefaultPipeline(OptimizationLevel Level,
// 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)));

5
lib/Transforms/IPO/PassManagerBuilder.cpp
View File

@ -680,6 +680,11 @@ void PassManagerBuilder::populateModulePassManager(
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);
}

1
test/Other/new-pm-defaults.ll
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@ -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
; CHECK-O-NEXT: Finished llvm::Function pass manager run.
; CHECK-O-NEXT: Running pass: GlobalDCEPass
; CHECK-O-NEXT: Running pass: ConstantMergePass

1
test/Other/pass-pipelines.ll
View File

@ -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

56
test/Other/pr32085.ll Normal file
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@ -0,0 +1,56 @@
; RUN: opt -S -O1 < %s -o %t1.ll
;; Show that there's no difference after running another simplify CFG
; RUN: opt -S -simplifycfg < %t1.ll -o %t2.ll
; RUN: diff %t1.ll %t2.ll
; 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.
@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
}