[IR] Make getIndexedOffsetInType return a signed result

A GEPed offset can go negative, the result of getIndexedOffsetInType
should according be a signed type.

llvm-svn: 275246
diff --git a/llvm/lib/Analysis/ConstantFolding.cpp b/llvm/lib/Analysis/ConstantFolding.cpp
index 0a9d725..c6dae24 100644
--- a/llvm/lib/Analysis/ConstantFolding.cpp
+++ b/llvm/lib/Analysis/ConstantFolding.cpp
@@ -920,7 +920,7 @@
   if (Instruction::isCast(Opcode))
     return ConstantFoldCastOperand(Opcode, Ops[0], DestTy, DL);
 
-  if(auto *GEP = dyn_cast<GEPOperator>(InstOrCE)) {
+  if (auto *GEP = dyn_cast<GEPOperator>(InstOrCE)) {
     if (Constant *C = SymbolicallyEvaluateGEP(GEP, Ops, DL, TLI))
       return C;