[PATCH] D136175: [BasicAA] Include MayBeCrossIteration in cache key

[Nikita Popov via Phabricator via llvm-commits]

nikic created this revision.
nikic added reviewers: reames, fhahn, asbirlea, jdoerfert.
Herald added subscribers: jeroen.dobbelaere, hiraditya.
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nikic requested review of this revision.
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Rather than switching to a new AAQI instance with empty cache when MayBeCrossIteration is toggled, include the value in the cache key.

The implementation redundantly include the information in both sides of the pair, but that seems simpler than trying to store it only on one side.

Depends on D136174 <https://reviews.llvm.org/D136174>.


https://reviews.llvm.org/D136175

Files:
  llvm/include/llvm/Analysis/AliasAnalysis.h
  llvm/lib/Analysis/BasicAliasAnalysis.cpp


Index: llvm/lib/Analysis/BasicAliasAnalysis.cpp
===================================================================
--- llvm/lib/Analysis/BasicAliasAnalysis.cpp
+++ llvm/lib/Analysis/BasicAliasAnalysis.cpp
@@ -1436,14 +1436,8 @@
   // different loop iterations.
   SaveAndRestore<bool> SavedMayBeCrossIteration(MayBeCrossIteration, true);
 
-  // If we enabled the MayBeCrossIteration flag, alias analysis results that
-  // have been cached earlier may no longer be valid. Perform recursive queries
-  // with a new AAQueryInfo.
-  AAQueryInfo NewAAQI = AAQI.withEmptyCache();
-  AAQueryInfo *UseAAQI = !SavedMayBeCrossIteration.get() ? &NewAAQI : &AAQI;
-
   AliasResult Alias = AAQI.AAR.alias(MemoryLocation(V1Srcs[0], PNSize),
-                                     MemoryLocation(V2, V2Size), *UseAAQI);
+                                     MemoryLocation(V2, V2Size), AAQI);
 
   // Early exit if the check of the first PHI source against V2 is MayAlias.
   // Other results are not possible.
@@ -1460,7 +1454,7 @@
     Value *V = V1Srcs[i];
 
     AliasResult ThisAlias = AAQI.AAR.alias(
-        MemoryLocation(V, PNSize), MemoryLocation(V2, V2Size), *UseAAQI);
+        MemoryLocation(V, PNSize), MemoryLocation(V2, V2Size), AAQI);
     Alias = MergeAliasResults(ThisAlias, Alias);
     if (Alias == AliasResult::MayAlias)
       break;
@@ -1578,7 +1572,8 @@
 
   // Check the cache before climbing up use-def chains. This also terminates
   // otherwise infinitely recursive queries.
-  AAQueryInfo::LocPair Locs({V1, V1Size}, {V2, V2Size});
+  AAQueryInfo::LocPair Locs({V1, V1Size, MayBeCrossIteration},
+                            {V2, V2Size, MayBeCrossIteration});
   const bool Swapped = V1 > V2;
   if (Swapped)
     std::swap(Locs.first, Locs.second);
Index: llvm/include/llvm/Analysis/AliasAnalysis.h
===================================================================
--- llvm/include/llvm/Analysis/AliasAnalysis.h
+++ llvm/include/llvm/Analysis/AliasAnalysis.h
@@ -192,21 +192,26 @@
 /// Reduced version of MemoryLocation that only stores a pointer and size.
 /// Used for caching AATags independent BasicAA results.
 struct AACacheLoc {
-  const Value *Ptr;
+  using PtrTy = PointerIntPair<const Value *, 1, bool>;
+  PtrTy Ptr;
   LocationSize Size;
+
+  AACacheLoc(PtrTy Ptr, LocationSize Size) : Ptr(Ptr), Size(Size) {}
+  AACacheLoc(const Value *Ptr, LocationSize Size, bool MayBeCrossIteration)
+      : Ptr(Ptr, MayBeCrossIteration), Size(Size) {}
 };
 
 template <> struct DenseMapInfo<AACacheLoc> {
   static inline AACacheLoc getEmptyKey() {
-    return {DenseMapInfo<const Value *>::getEmptyKey(),
+    return {DenseMapInfo<AACacheLoc::PtrTy>::getEmptyKey(),
             DenseMapInfo<LocationSize>::getEmptyKey()};
   }
   static inline AACacheLoc getTombstoneKey() {
-    return {DenseMapInfo<const Value *>::getTombstoneKey(),
+    return {DenseMapInfo<AACacheLoc::PtrTy>::getTombstoneKey(),
             DenseMapInfo<LocationSize>::getTombstoneKey()};
   }
   static unsigned getHashValue(const AACacheLoc &Val) {
-    return DenseMapInfo<const Value *>::getHashValue(Val.Ptr) ^
+    return DenseMapInfo<AACacheLoc::PtrTy>::getHashValue(Val.Ptr) ^
            DenseMapInfo<LocationSize>::getHashValue(Val.Size);
   }
   static bool isEqual(const AACacheLoc &LHS, const AACacheLoc &RHS) {


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