[llvm] 9cd4deb - [LoopVectorize] Preserve CFG analyses if CFG wasn't modified

[Max Kazantsev via llvm-commits]

Author: Max Kazantsev
Date: 2020-04-24T17:22:24+07:00
New Revision: 9cd4debd5ae43b03c96a2f8f24c73c5fd317d8ac

URL: https://github.com/llvm/llvm-project/commit/9cd4debd5ae43b03c96a2f8f24c73c5fd317d8ac
DIFF: https://github.com/llvm/llvm-project/commit/9cd4debd5ae43b03c96a2f8f24c73c5fd317d8ac.diff

LOG: [LoopVectorize] Preserve CFG analyses if CFG wasn't modified

One of transforms the loop vectorizer makes is LCSSA formation. In some cases it
is the only transform it makes. We should not drop CFG analyzes if only LCSSA was
formed and no actual CFG changes was made.

We should think of expanding this logic to other passes as well, and maybe make
it a part of PM framework.

Reviewed By: Florian Hahn
Differential Revision: https://reviews.llvm.org/D78360

Added: 
    

Modified: 
    llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h
    llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
    llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll

Removed: 
    


################################################################################
diff  --git a/llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h b/llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h
index 45313dc1db4e..22596b9d0bb7 100644
--- a/llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h
+++ b/llvm/include/llvm/Transforms/Vectorize/LoopVectorize.h
@@ -116,6 +116,15 @@ struct LoopVectorizeOptions {
   }
 };
 
+/// Storage for information about made changes.
+struct LoopVectorizeResult {
+  bool MadeAnyChange;
+  bool MadeCFGChange;
+
+  LoopVectorizeResult(bool MadeAnyChange, bool MadeCFGChange)
+      : MadeAnyChange(MadeAnyChange), MadeCFGChange(MadeCFGChange) {}
+};
+
 /// The LoopVectorize Pass.
 struct LoopVectorizePass : public PassInfoMixin<LoopVectorizePass> {
 private:
@@ -146,12 +155,13 @@ struct LoopVectorizePass : public PassInfoMixin<LoopVectorizePass> {
   PreservedAnalyses run(Function &F, FunctionAnalysisManager &AM);
 
   // Shim for old PM.
-  bool runImpl(Function &F, ScalarEvolution &SE_, LoopInfo &LI_,
-               TargetTransformInfo &TTI_, DominatorTree &DT_,
-               BlockFrequencyInfo &BFI_, TargetLibraryInfo *TLI_,
-               DemandedBits &DB_, AliasAnalysis &AA_, AssumptionCache &AC_,
-               std::function<const LoopAccessInfo &(Loop &)> &GetLAA_,
-               OptimizationRemarkEmitter &ORE_, ProfileSummaryInfo *PSI_);
+  LoopVectorizeResult
+  runImpl(Function &F, ScalarEvolution &SE_, LoopInfo &LI_,
+          TargetTransformInfo &TTI_, DominatorTree &DT_,
+          BlockFrequencyInfo &BFI_, TargetLibraryInfo *TLI_, DemandedBits &DB_,
+          AliasAnalysis &AA_, AssumptionCache &AC_,
+          std::function<const LoopAccessInfo &(Loop &)> &GetLAA_,
+          OptimizationRemarkEmitter &ORE_, ProfileSummaryInfo *PSI_);
 
   bool processLoop(Loop *L);
 };

diff  --git a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
index 7cb1695d05b3..c884548eb86b 100644
--- a/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
+++ b/llvm/lib/Transforms/Vectorize/LoopVectorize.cpp
@@ -1632,7 +1632,7 @@ struct LoopVectorize : public FunctionPass {
         [&](Loop &L) -> const LoopAccessInfo & { return LAA->getInfo(&L); };
 
     return Impl.runImpl(F, *SE, *LI, *TTI, *DT, *BFI, TLI, *DB, *AA, *AC,
-                        GetLAA, *ORE, PSI);
+                        GetLAA, *ORE, PSI).MadeAnyChange;
   }
 
   void getAnalysisUsage(AnalysisUsage &AU) const override {
@@ -7954,7 +7954,7 @@ bool LoopVectorizePass::processLoop(Loop *L) {
   return true;
 }
 
-bool LoopVectorizePass::runImpl(
+LoopVectorizeResult LoopVectorizePass::runImpl(
     Function &F, ScalarEvolution &SE_, LoopInfo &LI_, TargetTransformInfo &TTI_,
     DominatorTree &DT_, BlockFrequencyInfo &BFI_, TargetLibraryInfo *TLI_,
     DemandedBits &DB_, AliasAnalysis &AA_, AssumptionCache &AC_,
@@ -7982,9 +7982,9 @@ bool LoopVectorizePass::runImpl(
   // interleaving.
   if (!TTI->getNumberOfRegisters(TTI->getRegisterClassForType(true)) &&
       TTI->getMaxInterleaveFactor(1) < 2)
-    return false;
+    return LoopVectorizeResult(false, false);
 
-  bool Changed = false;
+  bool Changed = false, CFGChanged = false;
 
   // The vectorizer requires loops to be in simplified form.
   // Since simplification may add new inner loops, it has to run before the
@@ -7992,7 +7992,7 @@ bool LoopVectorizePass::runImpl(
   // will simplify all loops, regardless of whether anything end up being
   // vectorized.
   for (auto &L : *LI)
-    Changed |=
+    Changed |= CFGChanged |=
         simplifyLoop(L, DT, LI, SE, AC, nullptr, false /* PreserveLCSSA */);
 
   // Build up a worklist of inner-loops to vectorize. This is necessary as
@@ -8013,11 +8013,11 @@ bool LoopVectorizePass::runImpl(
     // transform.
     Changed |= formLCSSARecursively(*L, *DT, LI, SE);
 
-    Changed |= processLoop(L);
+    Changed |= CFGChanged |= processLoop(L);
   }
 
   // Process each loop nest in the function.
-  return Changed;
+  return LoopVectorizeResult(Changed, CFGChanged);
 }
 
 PreservedAnalyses LoopVectorizePass::run(Function &F,
@@ -8046,9 +8046,9 @@ PreservedAnalyses LoopVectorizePass::run(Function &F,
         AM.getResult<ModuleAnalysisManagerFunctionProxy>(F).getManager();
     ProfileSummaryInfo *PSI =
         MAM.getCachedResult<ProfileSummaryAnalysis>(*F.getParent());
-    bool Changed =
+    LoopVectorizeResult Result =
         runImpl(F, SE, LI, TTI, DT, BFI, &TLI, DB, AA, AC, GetLAA, ORE, PSI);
-    if (!Changed)
+    if (!Result.MadeAnyChange)
       return PreservedAnalyses::all();
     PreservedAnalyses PA;
 
@@ -8062,5 +8062,7 @@ PreservedAnalyses LoopVectorizePass::run(Function &F,
     }
     PA.preserve<BasicAA>();
     PA.preserve<GlobalsAA>();
+    if (!Result.MadeCFGChange)
+      PA.preserveSet<CFGAnalyses>();
     return PA;
 }

diff  --git a/llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll b/llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll
index b1e424711cf4..05b36f8c550b 100644
--- a/llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll
+++ b/llvm/test/Transforms/LoopVectorize/novect-lcssa-cfg-invalidation.ll
@@ -11,8 +11,8 @@ define i32 @novect(i32* %p) {
 ; CHECK:           Invalidating all non-preserved analyses for: novect
 ; CHECK:           Clearing all analysis results for: <possibly invalidated loop>
 ; CHECK:           Invalidating analysis: ScalarEvolutionAnalysis on novect
-; CHECK:           Invalidating analysis: BranchProbabilityAnalysis on novect
-; CHECK:           Invalidating analysis: BlockFrequencyAnalysis on novect
+; CHECK-NOT:       Invalidating analysis: BranchProbabilityAnalysis on novect
+; CHECK-NOT:       Invalidating analysis: BlockFrequencyAnalysis on novect
 ; CHECK:           Invalidating analysis: DemandedBitsAnalysis on novect
 ; CHECK:           Invalidating analysis: MemorySSAAnalysis on novect
 ; CHECK:           Running pass: JumpThreadingPass on novect