replace usage of EmitGEPOffset() with TargetData::getIndexedOffset() when the GEP offset is known to be constant.

With this change, we avoid relying on the IR Builder to constant fold the operations.

No functionality change intended.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@158829 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 6 insertions, 8 deletions

diff --git a/lib/Transforms/InstCombine/InstCombineCasts.cpp b/lib/Transforms/InstCombine/InstCombineCasts.cpp
index d07be2c..fa24800 100644
--- a/lib/Transforms/InstCombine/InstCombineCasts.cpp
+++ b/lib/Transforms/InstCombine/InstCombineCasts.cpp
@@ -1341,10 +1341,9 @@ Instruction *InstCombiner::commonPointerCastTransforms(CastInst &CI) {
     // non-type-safe code.
     if (TD && GEP->hasOneUse() && isa<BitCastInst>(GEP->getOperand(0)) &&
         GEP->hasAllConstantIndices()) {
-      // We are guaranteed to get a constant from EmitGEPOffset.
-      ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(GEP));
-      int64_t Offset = OffsetV->getSExtValue();
-      
+      SmallVector<Value*, 8> Ops(GEP->idx_begin(), GEP->idx_end());
+      int64_t Offset = TD->getIndexedOffset(GEP->getPointerOperandType(), Ops);
+
       // Get the base pointer input of the bitcast, and the type it points to.
       Value *OrigBase = cast<BitCastInst>(GEP->getOperand(0))->getOperand(0);
       Type *GEPIdxTy =
diff --git a/lib/Transforms/InstCombine/InstructionCombining.cpp b/lib/Transforms/InstCombine/InstructionCombining.cpp
index b8a533b..2548ac1 100644
--- a/lib/Transforms/InstCombine/InstructionCombining.cpp
+++ b/lib/Transforms/InstCombine/InstructionCombining.cpp
@@ -1058,10 +1058,9 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
         !isa<BitCastInst>(BCI->getOperand(0)) && GEP.hasAllConstantIndices() &&
         StrippedPtrTy->getAddressSpace() == GEP.getPointerAddressSpace()) {
 
-      // Determine how much the GEP moves the pointer.  We are guaranteed to get
-      // a constant back from EmitGEPOffset.
-      ConstantInt *OffsetV = cast<ConstantInt>(EmitGEPOffset(&GEP));
-      int64_t Offset = OffsetV->getSExtValue();
+      // Determine how much the GEP moves the pointer.
+      SmallVector<Value*, 8> Ops(GEP.idx_begin(), GEP.idx_end());
+      int64_t Offset = TD->getIndexedOffset(GEP.getPointerOperandType(), Ops);
 
       // If this GEP instruction doesn't move the pointer, just replace the GEP
       // with a bitcast of the real input to the dest type.