On 64-bit targets, change 32-bit getelementptr indices to be 64-bit

getelementptr indices, inserting an explicit cast if necessary.
This helps expose the sign-extension operation to other optimizations.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@56133 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/Transforms/Scalar/InstructionCombining.cpp b/lib/Transforms/Scalar/InstructionCombining.cpp
index f02a7108fd..1cb4fa2c21 100644
--- a/lib/Transforms/Scalar/InstructionCombining.cpp
+++ b/lib/Transforms/Scalar/InstructionCombining.cpp
@@ -9795,7 +9795,8 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
         }
       }
       // If we are using a wider index than needed for this platform, shrink it
-      // to what we need.  If the incoming value needs a cast instruction,
+      // to what we need.  If narrower, sign-extend it to what we need.
+      // If the incoming value needs a cast instruction,
       // insert it.  This explicit cast can make subsequent optimizations more
       // obvious.
       Value *Op = *i;
@@ -9809,6 +9810,16 @@ Instruction *InstCombiner::visitGetElementPtrInst(GetElementPtrInst &GEP) {
           *i = Op;
           MadeChange = true;
         }
+      } else if (TD->getTypeSizeInBits(Op->getType()) < TD->getPointerSizeInBits()) {
+        if (Constant *C = dyn_cast<Constant>(Op)) {
+          *i = ConstantExpr::getSExt(C, TD->getIntPtrType());
+          MadeChange = true;
+        } else {
+          Op = InsertCastBefore(Instruction::SExt, Op, TD->getIntPtrType(),
+                                GEP);
+          *i = Op;
+          MadeChange = true;
+        }
       }
     }
   }