[ConstantFolding] Avoid some uses of ConstantExpr::getCast()

Call the constant folding API instead.

Author: nikic

llvm/lib/Analysis/ConstantFolding.cpp

@@ -383,7 +383,7 @@ Constant *llvm::ConstantFoldLoadThroughBitcast(Constant *C, Type *DestTy,
         Cast = Instruction::PtrToInt;
 
       if (CastInst::castIsValid(Cast, C, DestTy))
-        return ConstantExpr::getCast(Cast, C, DestTy);
+        return ConstantFoldCastOperand(Cast, C, DestTy, DL);
     }
 
     // If this isn't an aggregate type, there is nothing we can do to drill down
@@ -846,14 +846,14 @@ Constant *CastGEPIndices(Type *SrcElemTy, ArrayRef<Constant *> Ops,
              SrcElemTy, Ops.slice(1, i - 1)))) &&
         Ops[i]->getType()->getScalarType() != IntIdxScalarTy) {
       Any = true;
-      Type *NewType = Ops[i]->getType()->isVectorTy()
-                          ? IntIdxTy
-                          : IntIdxScalarTy;
-      NewIdxs.push_back(ConstantExpr::getCast(CastInst::getCastOpcode(Ops[i],
-                                                                      true,
-                                                                      NewType,
-                                                                      true),
-                                              Ops[i], NewType));
+      Type *NewType =
+          Ops[i]->getType()->isVectorTy() ? IntIdxTy : IntIdxScalarTy;
+      Constant *NewIdx = ConstantFoldCastOperand(
+          CastInst::getCastOpcode(Ops[i], true, NewType, true), Ops[i], NewType,
+          DL);
+      if (!NewIdx)
+        return nullptr;
+      NewIdxs.push_back(NewIdx);
     } else
       NewIdxs.push_back(Ops[i]);
   }