Strengthen GetUnderlyingObject using InstructionSimplify.

While LLVM's main design is that analysis code shouldn't
go out of its way to understand code which hasn't been
InstCombined, analysis utility routines like this can
find themselves being called in the middle of transform
passes when instcombine hasn't had a chance to run.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@121886 91177308-0d34-0410-b5e6-96231b3b80d8

diff --git a/lib/Analysis/ValueTracking.cpp b/lib/Analysis/ValueTracking.cpp
index d1b75c3f9fc4ebc08b5ba90359efdac2b6aa9b2b..75062953cbac1a173ca9fc52629c105d3752251c 100644 (file)
--- a/lib/Analysis/ValueTracking.cpp
+++ b/lib/Analysis/ValueTracking.cpp
@@ -13,6 +13,7 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/Analysis/ValueTracking.h"
+#include "llvm/Analysis/InstructionSimplify.h"
 #include "llvm/Constants.h"
 #include "llvm/Instructions.h"
 #include "llvm/GlobalVariable.h"
@@ -1440,6 +1441,14 @@ Value *llvm::GetUnderlyingObject(Value *V, unsigned MaxLookup) {
         return V;
       V = GA->getAliasee();
     } else {
+      // See if InstructionSimplify knows any relevant tricks.
+      if (Instruction *I = dyn_cast<Instruction>(V))
+        // TODO: Aquire TargetData and DominatorTree and use them.
+        if (Value *Simplified = SimplifyInstruction(I, 0, 0)) {
+          V = Simplified;
+          continue;
+        }
+
       return V;
     }
     assert(V->getType()->isPointerTy() && "Unexpected operand type!");