On Fri, Feb 22, 2013 at 12:33 PM, Andrew Pinski <pins...@gmail.com> wrote: > On Thu, Feb 21, 2013 at 8:31 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: >> On Fri, Feb 22, 2013 at 12:14 PM, Andrew Pinski <pins...@gmail.com> wrote: >>> On Thu, Feb 21, 2013 at 7:16 PM, Bin.Cheng <amker.ch...@gmail.com> wrote: >>>> Hi, >>>> GCCINT says that nop_expr is used to represent conversions that do not >>>> require any code generation, while function tree_strip_nop_conversions >>>> calls tree_nop_conversion, which returns false even for NOP_EXPR node >>>> like "(unsigned int)a", where a has type int. >>> >>> Are you sure a has the type of int? >>> >>> The code does: >>> if ((INTEGRAL_TYPE_P (outer_type) >>> || POINTER_TYPE_P (outer_type) >>> || TREE_CODE (outer_type) == OFFSET_TYPE) >>> && (INTEGRAL_TYPE_P (inner_type) >>> || POINTER_TYPE_P (inner_type) >>> || TREE_CODE (inner_type) == OFFSET_TYPE)) >>> return TYPE_PRECISION (outer_type) == TYPE_PRECISION (inner_type); >>> >>> Which will return true for the case you mentioned. Also NOP_EXPR and >>> CONVERT_EXPR are handled almost the same through out the whole >>> compiler. >>> >> Oh, sorry about the mistake, a has type of signed short. Maybe we can >> improve tree_nop_conversion with this case. > > No because it is not a true nop conversion. The whole NOP_EXPR vs > CONVERT_EXPR has been going on for a while now. I was trying to make > the point to the middle-end NOP_EXPR and CONVERT_EXPR are exactly the > same and the documentation about NOP_EXPR being a conversion which > makes no code is incorrect. >
Thanks for your explanation. -- Best Regards.
