Enhance GVN to do more precise alias queries for non-local memory

references. For example, this allows gvn to eliminate the load in
this example:

  void foo(int n, int* p, int *q) {
    p[0] = 0;
    p[1] = 1;
    if (n) {
      *q = p[0];
    }
  }


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@118714 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 11 insertions, 10 deletions

diff --git a/include/llvm/Analysis/AliasAnalysis.h b/include/llvm/Analysis/AliasAnalysis.h
index 17abae4eb9..302204e41b 100644
--- a/include/llvm/Analysis/AliasAnalysis.h
+++ b/include/llvm/Analysis/AliasAnalysis.h
@@ -107,6 +107,12 @@ public:
       return Copy;
     }
 
+    Location getWithNewSize(uint64_t NewSize) const {
+      Location Copy(*this);
+      Copy.Size = NewSize;
+      return Copy;
+    }
+
     Location getWithoutTBAATag() const {
       Location Copy(*this);
       Copy.TBAATag = 0;
diff --git a/include/llvm/Analysis/MemoryDependenceAnalysis.h b/include/llvm/Analysis/MemoryDependenceAnalysis.h
index b5c68f6833..c1a1536037 100644
--- a/include/llvm/Analysis/MemoryDependenceAnalysis.h
+++ b/include/llvm/Analysis/MemoryDependenceAnalysis.h
@@ -227,11 +227,14 @@ namespace llvm {
       BBSkipFirstBlockPair Pair;
       /// NonLocalDeps - The results of the query for each relevant block.
       NonLocalDepInfo NonLocalDeps;
+      /// Size - The maximum size of the dereferences of the
+      /// pointer. May be UnknownSize if the sizes are unknown.
+      uint64_t Size;
       /// TBAATag - The TBAA tag associated with dereferences of the
       /// pointer. May be null if there are no tags or conflicting tags.
-      MDNode *TBAATag;
+      const MDNode *TBAATag;
 
-      NonLocalPointerInfo() : TBAATag(0) {}
+      NonLocalPointerInfo() : Size(0), TBAATag(0) {}
     };
 
     /// CachedNonLocalPointerInfo - This map stores the cached results of doing
@@ -315,14 +318,6 @@ namespace llvm {
                                       bool isLoad, BasicBlock *BB,
                                     SmallVectorImpl<NonLocalDepResult> &Result);
 
-    /// getNonLocalPointerDependence - A convenience wrapper.
-    void getNonLocalPointerDependency(Value *Pointer, bool isLoad,
-                                      BasicBlock *BB,
-                                    SmallVectorImpl<NonLocalDepResult> &Result){
-      return getNonLocalPointerDependency(AliasAnalysis::Location(Pointer),
-                                          isLoad, BB, Result);
-    }
-    
     /// removeInstruction - Remove an instruction from the dependence analysis,
     /// updating the dependence of instructions that previously depended on it.
     void removeInstruction(Instruction *InstToRemove);