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];
    }
  }

llvm-svn: 118714

1 files changed, 4 insertions, 2 deletions

diff --git a/llvm/lib/Transforms/Scalar/GVN.cpp b/llvm/lib/Transforms/Scalar/GVN.cpp
index a2fcca59841..e506d0efd7f 100644
--- a/llvm/lib/Transforms/Scalar/GVN.cpp
+++ b/llvm/lib/Transforms/Scalar/GVN.cpp
@@ -1351,8 +1351,10 @@ bool GVN::processNonLocalLoad(LoadInst *LI,
                               SmallVectorImpl<Instruction*> &toErase) {
   // Find the non-local dependencies of the load.
   SmallVector<NonLocalDepResult, 64> Deps;
-  MD->getNonLocalPointerDependency(LI->getPointerOperand(), true,
-                                   LI->getParent(),
+  AliasAnalysis::Location Loc(LI->getPointerOperand(),
+                         VN.getAliasAnalysis()->getTypeStoreSize(LI->getType()),
+                              LI->getMetadata(LLVMContext::MD_tbaa));
+  MD->getNonLocalPointerDependency(Loc, true, LI->getParent(),
                                    Deps);
   //DEBUG(dbgs() << "INVESTIGATING NONLOCAL LOAD: "
   //             << Deps.size() << *LI << '\n');