Factorize code: remove variants of "strip off

pointer bitcasts and GEP's", and centralize the
logic in Value::getUnderlyingObject.  The
difference with stripPointerCasts is that
stripPointerCasts only strips GEPs if all
indices are zero, while getUnderlyingObject
strips GEPs no matter what the indices are.

llvm-svn: 56922

1 files changed, 1 insertions, 23 deletions

diff --git a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
index 6cac395405b..4f489718f6f 100644
--- a/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/llvm/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -10367,28 +10367,6 @@ static bool isSafeToLoadUnconditionally(Value *V, Instruction *ScanFrom) {
   return false;
 }
 
-/// GetUnderlyingObject - Trace through a series of getelementptrs and bitcasts
-/// until we find the underlying object a pointer is referring to or something
-/// we don't understand.  Note that the returned pointer may be offset from the
-/// input, because we ignore GEP indices.
-static Value *GetUnderlyingObject(Value *Ptr) {
-  while (1) {
-    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
-      if (CE->getOpcode() == Instruction::BitCast ||
-          CE->getOpcode() == Instruction::GetElementPtr)
-        Ptr = CE->getOperand(0);
-      else
-        return Ptr;
-    } else if (BitCastInst *BCI = dyn_cast<BitCastInst>(Ptr)) {
-      Ptr = BCI->getOperand(0);
-    } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(Ptr)) {
-      Ptr = GEP->getOperand(0);
-    } else {
-      return Ptr;
-    }
-  }
-}
-
 Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
   Value *Op = LI.getOperand(0);
 
@@ -10479,7 +10457,7 @@ Instruction *InstCombiner::visitLoadInst(LoadInst &LI) {
     
   // If this load comes from anywhere in a constant global, and if the global
   // is all undef or zero, we know what it loads.
-  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(GetUnderlyingObject(Op))) {
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Op->getUnderlyingObject())){
     if (GV->isConstant() && GV->hasInitializer()) {
       if (GV->getInitializer()->isNullValue())
         return ReplaceInstUsesWith(LI, Constant::getNullValue(LI.getType()));