On Thu, Jun 8, 2017 at 4:33 AM, Martin Sebor <mse...@gmail.com> wrote: > On 06/07/2017 02:12 PM, Martin Sebor wrote: >> >> On 06/07/2017 02:01 PM, Marc Glisse wrote: >>> >>> On Wed, 7 Jun 2017, Bernhard Reutner-Fischer wrote: >>> >>>> On 7 June 2017 16:46:53 CEST, Martin Sebor <mse...@gmail.com> wrote: >>>>> >>>>> On 06/07/2017 02:23 AM, Richard Biener wrote: >>>>>> >>>>>> On Wed, Jun 7, 2017 at 5:26 AM, Martin Sebor <mse...@gmail.com> >>>>> >>>>> wrote: >>>>>>>> >>>>>>>> Note I'd be _much_ more sympathetic to simply canonicalizing all of >>>>>>>> bzero and bcopy >>>>>>>> to memset / memmove and be done with all the above complexity. >>>>>>> >>>>>>> >>>>>>> >>>>>>> Attached is an updated patch along these lines. Please let me >>>>>>> know if it matches your expectations. >>>>>> >>>>>> >>>>>> I think you attached the wrong patch. >>>>> >>>>> >>>>> Yes I did, sorry. The correct one is attached. >>>> >>>> >>>> Under POSIX.1-2008 "optimizing" bzero or bcmp is IMO plain wrong. >>>> >>>> It's like optimizing foo() to a random built-in but maybe that's just >>>> me. If your libc provides a define to a standard function for these >>>> under a compat knob then fine but otherwise you should fix that. >>>> *shrug*. Joseph? >>> >>> >>> The patch optimizes __builtin_bzero, which should be ok. The question >>> (independent from this patch) is then under what conditions bzero should >>> be detected as a builtin. >> >> >> Yes. The problem is that unlike for C and C++, GCC doesn't have >> a mechanism to select the target version of POSIX. I think it >> should. >> >> But there is a subtle problem with the patch that needs fixing. >> Bcopy should not be transformed to memcpy but rather memmove. >> I'll fix that before committing. > > > Attached is an updated patch with this fix. I also added a cast > from bcopy and bzero to void to detect accidental uses of the > return value. Tested on x86_64-linux.
Please do not add foldings to builtins.c but instead add them to gimple-fold.c. + /* Call memset and return the result cast to void to detect its use + (bzero returns void). */ + tree call = build_call_expr_loc (loc, fn, 3, dst, integer_zero_node, len); + return fold_convert (void_type_node, call); ??? How can the result be used if the original call result was not? Thanks, Richard. > Martin
