[PATCH] D40035: [LoopRotate] processLoop should return true even if it just simplified the loop latch without making any other changes

[Craig Topper via Phabricator via llvm-commits]

craig.topper updated this revision to Diff 122888.
craig.topper added a comment.

Now with test case.


https://reviews.llvm.org/D40035

Files:
  lib/Transforms/Scalar/LoopRotation.cpp
  test/Transforms/LoopRotate/pr35210.ll


Index: test/Transforms/LoopRotate/pr35210.ll
===================================================================
--- /dev/null
+++ test/Transforms/LoopRotate/pr35210.ll
@@ -0,0 +1,70 @@
+;RUN: opt %s -passes='adce,loop(rotate),adce' -S -debug-pass-manager -debug-only=loop-rotate 2>&1 | FileCheck %s
+
+; This test is to make sure we invalidate the post dominator pass after loop rotate simplifies the loop latch.
+; The adce passes are here to make sure post dominator analysis is required.
+
+; CHECK: Starting llvm::Function pass manager run.
+; CHECK-NEXT: Running pass: ADCEPass on f
+; CHECK-NEXT: Running analysis: DominatorTreeAnalysis on f
+; CHECK-NEXT: Running analysis: PostDominatorTreeAnalysis on f
+; CHECK-NEXT: Running pass: FunctionToLoopPassAdaptor<llvm::PassManager<llvm::Loop, llvm::LoopAnalysisManager, llvm::LoopStandardAnalysisResults &, llvm::LPMUpdater &> > on f
+; CHECK-NEXT: Running analysis: LoopAnalysis on f
+; CHECK-NEXT: Running analysis: AssumptionAnalysis on f
+; CHECK-NEXT: Running analysis: AAManager on f
+; CHECK-NEXT: Running analysis: TargetLibraryAnalysis on f
+; CHECK-NEXT: Running analysis: ScalarEvolutionAnalysis on f
+; CHECK-NEXT: Running analysis: TargetIRAnalysis on f
+; CHECK-NEXT: Running analysis: InnerAnalysisManagerProxy<llvm::LoopAnalysisManager, llvm::Function> on f
+; CHECK-NEXT: Starting Loop pass manager run.
+; CHECK-NEXT: Running pass: LoopRotatePass on Loop at depth 1 containing: %bb<header><exiting>,%bb4<latch>
+; CHECK-NEXT: Folding loop latch bb4 into bb
+; CHECK-NEXT: Invalidating all non-preserved analyses for: bb
+; CHECK-NEXT: Finished Loop pass manager run.
+; CHECK-NEXT: Invalidating all non-preserved analyses for: f
+; CHECK-NEXT: Invalidating analysis: PostDominatorTreeAnalysis on f
+; CHECK-NEXT: Running pass: ADCEPass on f
+; CHECK-NEXT: Running analysis: PostDominatorTreeAnalysis on f
+; CHECK-NEXT: Finished llvm::Function pass manager run.
+
+; CHECK-LABEL: define i8 @f() {
+; CHECK-NEXT : entry:
+; CHECK-NEXT :   br label %bb
+; CHECK-NEXT :
+; CHECK-NEXT : bb:                                               ; preds = %bb, %entry
+; CHECK-NEXT :   %mode.0 = phi i8 [ 0, %entry ], [ %indvar.next, %bb ]
+; CHECK-NEXT :   %tmp5 = icmp eq i8 %mode.0, 1
+; CHECK-NEXT :   %indvar.next = add i8 %mode.0, 1
+; CHECK-NEXT :   br i1 %tmp5, label %bb5, label %bb
+; CHECK-NEXT :
+; CHECK-NEXT : bb5:                                              ; preds = %bb
+; CHECK-NEXT :   tail call void @raise_exception() #0
+; CHECK-NEXT :   unreachable
+; CHECK-NEXT : }
+; CHECK-NEXT :
+; CHECK-NEXT : ; Function Attrs: noreturn
+; CHECK-NEXT : declare void @raise_exception() #0
+; CHECK-NEXT :
+; CHECK-NEXT : attributes #0 = { noreturn }
+
+define i8 @f() {
+entry:
+  br label %bb
+
+bb:                                               ; preds = %bb4, %entry
+  %mode.0 = phi i8 [ 0, %entry ], [ %indvar.next, %bb4 ]
+  %tmp5 = icmp eq i8 %mode.0, 1
+  br i1 %tmp5, label %bb5, label %bb4
+
+bb4:                                              ; preds = %bb2
+  %indvar.next = add i8 %mode.0, 1
+  br label %bb
+
+bb5:                                              ; preds = %bb2
+  tail call void @raise_exception() #0
+  unreachable
+}
+
+; Function Attrs: noreturn
+declare void @raise_exception() #0
+
+attributes #0 = { noreturn }
Index: lib/Transforms/Scalar/LoopRotation.cpp
===================================================================
--- lib/Transforms/Scalar/LoopRotation.cpp
+++ lib/Transforms/Scalar/LoopRotation.cpp
@@ -634,7 +634,7 @@
   if ((MadeChange || SimplifiedLatch) && LoopMD)
     L->setLoopID(LoopMD);
 
-  return MadeChange;
+  return MadeChange || SimplifiedLatch;
 }
 
 LoopRotatePass::LoopRotatePass(bool EnableHeaderDuplication)


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