From 6d98f3a6dfa392b2c87a0e55d0d2aa4685faba0d Mon Sep 17 00:00:00 2001
From: Nikita Popov <npopov@redhat.com>
Date: Mon, 14 Nov 2022 15:28:09 +0100
Subject: [PATCH] [LoopVersioningLICM] Clarify scope of AST (NFC)

Make it clearer that the AST is only temporarily used during the
legality check, and does not have to survive into the transformation
phase.
---
 llvm/lib/Transforms/Scalar/LoopVersioningLICM.cpp | 45 +++++++++++------------
 1 file changed, 22 insertions(+), 23 deletions(-)

diff --git a/llvm/lib/Transforms/Scalar/LoopVersioningLICM.cpp b/llvm/lib/Transforms/Scalar/LoopVersioningLICM.cpp
index 65df1aa..38ebfe5 100644
--- a/llvm/lib/Transforms/Scalar/LoopVersioningLICM.cpp
+++ b/llvm/lib/Transforms/Scalar/LoopVersioningLICM.cpp
@@ -147,13 +147,13 @@ struct LoopVersioningLICM {
   // LoopAccessInfo will take place only when it's necessary.
   LoopVersioningLICM(AliasAnalysis *AA, ScalarEvolution *SE,
                      OptimizationRemarkEmitter *ORE,
-                     LoopAccessInfoManager &LAIs,
+                     LoopAccessInfoManager &LAIs, LoopInfo &LI,
                      Loop *CurLoop)
-      : AA(AA), SE(SE), LAIs(LAIs), CurLoop(CurLoop), AST(*AA),
+      : AA(AA), SE(SE), LAIs(LAIs), LI(LI), CurLoop(CurLoop),
         LoopDepthThreshold(LVLoopDepthThreshold),
         InvariantThreshold(LVInvarThreshold), ORE(ORE) {}
 
-  bool run(LoopInfo *LI, DominatorTree *DT);
+  bool run(DominatorTree *DT);
 
 private:
   // Current AliasAnalysis information
@@ -168,12 +168,11 @@ private:
   // Proxy for retrieving LoopAccessInfo.
   LoopAccessInfoManager &LAIs;
 
+  LoopInfo &LI;
+
   // The current loop we are working on.
   Loop *CurLoop;
 
-  // AliasSet information for the current loop.
-  AliasSetTracker AST;
-
   // Maximum loop nest threshold
   unsigned LoopDepthThreshold;
 
@@ -256,9 +255,14 @@ bool LoopVersioningLICM::legalLoopStructure() {
 /// Check memory accesses in loop and confirms it's good for
 /// LoopVersioningLICM.
 bool LoopVersioningLICM::legalLoopMemoryAccesses() {
-  bool HasMayAlias = false;
-  bool TypeSafety = false;
-  bool HasMod = false;
+  // Loop over the body of this loop, construct AST.
+  AliasSetTracker AST(*AA);
+  for (auto *Block : CurLoop->getBlocks()) {
+    // Ignore blocks in subloops.
+    if (LI.getLoopFor(Block) == CurLoop)
+      AST.add(*Block);
+  }
+
   // Memory check:
   // Transform phase will generate a versioned loop and also a runtime check to
   // ensure the pointers are independent and they don’t alias.
@@ -271,6 +275,9 @@ bool LoopVersioningLICM::legalLoopMemoryAccesses() {
   //
   // Iterate over alias tracker sets, and confirm AliasSets doesn't have any
   // must alias set.
+  bool HasMayAlias = false;
+  bool TypeSafety = false;
+  bool HasMod = false;
   for (const auto &I : AST) {
     const AliasSet &AS = I;
     // Skip Forward Alias Sets, as this should be ignored as part of
@@ -563,25 +570,18 @@ bool LoopVersioningLICMLegacyPass::runOnLoop(Loop *L, LPPassManager &LPM) {
   ScalarEvolution *SE = &getAnalysis<ScalarEvolutionWrapperPass>().getSE();
   OptimizationRemarkEmitter *ORE =
       &getAnalysis<OptimizationRemarkEmitterWrapperPass>().getORE();
-  LoopInfo *LI = &getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
+  LoopInfo &LI = getAnalysis<LoopInfoWrapperPass>().getLoopInfo();
   DominatorTree *DT = &getAnalysis<DominatorTreeWrapperPass>().getDomTree();
   auto &LAIs = getAnalysis<LoopAccessLegacyAnalysis>().getLAIs();
 
-  return LoopVersioningLICM(AA, SE, ORE, LAIs, L).run(LI, DT);
+  return LoopVersioningLICM(AA, SE, ORE, LAIs, LI, L).run(DT);
 }
 
-bool LoopVersioningLICM::run(LoopInfo *LI, DominatorTree *DT) {
+bool LoopVersioningLICM::run(DominatorTree *DT) {
   // Do not do the transformation if disabled by metadata.
   if (hasLICMVersioningTransformation(CurLoop) & TM_Disable)
     return false;
 
-  // Loop over the body of this loop, construct AST.
-  for (auto *Block : CurLoop->getBlocks()) {
-    // Ignore blocks in subloops.
-    if (LI->getLoopFor(Block) == CurLoop)
-      AST.add(*Block); // Incorporate the specified basic block
-  }
-
   bool Changed = false;
 
   // Check feasiblity of LoopVersioningLICM.
@@ -592,7 +592,7 @@ bool LoopVersioningLICM::run(LoopInfo *LI, DominatorTree *DT) {
     // Create memcheck for memory accessed inside loop.
     // Clone original loop, and set blocks properly.
     LoopVersioning LVer(*LAI, LAI->getRuntimePointerChecking()->getChecks(),
-                        CurLoop, LI, DT, SE);
+                        CurLoop, &LI, DT, SE);
     LVer.versionLoop();
     // Set Loop Versioning metaData for original loop.
     addStringMetadataToLoop(LVer.getNonVersionedLoop(), LICMVersioningMetaData);
@@ -638,12 +638,11 @@ PreservedAnalyses LoopVersioningLICMPass::run(Loop &L, LoopAnalysisManager &AM,
   AliasAnalysis *AA = &LAR.AA;
   ScalarEvolution *SE = &LAR.SE;
   DominatorTree *DT = &LAR.DT;
-  LoopInfo *LI = &LAR.LI;
   const Function *F = L.getHeader()->getParent();
   OptimizationRemarkEmitter ORE(F);
 
-  LoopAccessInfoManager LAIs(*SE, *AA, *DT, *LI, nullptr);
-  if (!LoopVersioningLICM(AA, SE, &ORE, LAIs, &L).run(LI, DT))
+  LoopAccessInfoManager LAIs(*SE, *AA, *DT, LAR.LI, nullptr);
+  if (!LoopVersioningLICM(AA, SE, &ORE, LAIs, LAR.LI, &L).run(DT))
     return PreservedAnalyses::all();
   return getLoopPassPreservedAnalyses();
 }
-- 
2.7.4