[PATCH] Merge metadata in the AliasSetTracker (and refactor merging)

[hfinkel at anl.gov]

Hi dberlin, chandlerc,

Refactor how AA metadata merging is done, and allow the AliasSetTracker to merge non-equal metadata when merging access sets instead of just dropping all AA metadata when unequal.

I no longer have an in-tree test case for this change, so I'll need to try making one.

http://reviews.llvm.org/D9396

Files:
  include/llvm/Analysis/AliasSetTracker.h
  include/llvm/IR/Metadata.h
  lib/Analysis/TypeBasedAliasAnalysis.cpp

Index: include/llvm/Analysis/AliasSetTracker.h
===================================================================
--- include/llvm/Analysis/AliasSetTracker.h
+++ include/llvm/Analysis/AliasSetTracker.h
@@ -64,8 +64,7 @@
         // We don't have a AAInfo yet. Set it to NewAAInfo.
         AAInfo = NewAAInfo;
       else if (AAInfo != NewAAInfo)
-        // NewAAInfo conflicts with AAInfo.
-        AAInfo = DenseMapInfo<AAMDNodes>::getTombstoneKey();
+        AAInfo.merge(NewAAInfo);
     }
 
     uint64_t getSize() const { return Size; }
Index: include/llvm/IR/Metadata.h
===================================================================
--- include/llvm/IR/Metadata.h
+++ include/llvm/IR/Metadata.h
@@ -546,6 +546,8 @@
 
   explicit operator bool() const { return TBAA || Scope || NoAlias; }
 
+  void merge(const AAMDNodes &N);
+
   /// \brief The tag for type-based alias analysis.
   MDNode *TBAA;
 
Index: lib/Analysis/TypeBasedAliasAnalysis.cpp
===================================================================
--- lib/Analysis/TypeBasedAliasAnalysis.cpp
+++ lib/Analysis/TypeBasedAliasAnalysis.cpp
@@ -623,23 +623,22 @@
   return MDNode::get(A->getContext(), Ops);
 }
 
+void AAMDNodes::merge(const AAMDNodes &N) {
+  TBAA = MDNode::getMostGenericTBAA(TBAA, N.TBAA);
+  Scope = MDNode::getMostGenericAliasScope(Scope, N.Scope);
+  NoAlias = MDNode::intersect(NoAlias, N.NoAlias);
+}
+
 void Instruction::getAAMetadata(AAMDNodes &N, bool Merge) const {
-  if (Merge)
-    N.TBAA =
-        MDNode::getMostGenericTBAA(N.TBAA, getMetadata(LLVMContext::MD_tbaa));
-  else
-    N.TBAA = getMetadata(LLVMContext::MD_tbaa);
-
-  if (Merge)
-    N.Scope = MDNode::getMostGenericAliasScope(
-        N.Scope, getMetadata(LLVMContext::MD_alias_scope));
-  else
-    N.Scope = getMetadata(LLVMContext::MD_alias_scope);
-
-  if (Merge)
-    N.NoAlias =
-        MDNode::intersect(N.NoAlias, getMetadata(LLVMContext::MD_noalias));
-  else
-    N.NoAlias = getMetadata(LLVMContext::MD_noalias);
+  if (Merge) {
+    AAMDNodes M;
+    getAAMetadata(M);
+    N.merge(M);
+    return;
+  }
+
+  N.TBAA = getMetadata(LLVMContext::MD_tbaa);
+  N.Scope = getMetadata(LLVMContext::MD_alias_scope);
+  N.NoAlias = getMetadata(LLVMContext::MD_noalias);
 }

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