Use getIndexTypeBitwidth instead of hardcoded 64.

Author: abidh

flang/lib/Optimizer/Transforms/DebugTypeGenerator.cpp

@@ -582,7 +582,8 @@ DebugTypeGenerator::convertType(mlir::Type Ty, mlir::LLVM::DIFileAttr fileAttr,
   } else if (auto vecTy = mlir::dyn_cast_or_null<fir::VectorType>(Ty)) {
     return convertVectorType(vecTy, fileAttr, scope, declOp);
   } else if (mlir::isa<mlir::IndexType>(Ty)) {
-    return genBasicType(context, mlir::StringAttr::get(context, "integer"), 64,
+    return genBasicType(context, mlir::StringAttr::get(context, "integer"),
+                        llvmTypeConverter.getIndexTypeBitwidth(),
                         llvm::dwarf::DW_ATE_signed);
   } else if (auto boxTy = mlir::dyn_cast_or_null<fir::BoxType>(Ty)) {
     auto elTy = boxTy.getElementType();