On Thu, May 9, 2019 at 5:31 AM Jeff Law <l...@redhat.com> wrote: > > On 5/8/19 6:28 AM, Richard Biener wrote: > > On Wed, May 8, 2019 at 12:09 PM JunMa <ju...@linux.alibaba.com> wrote: > >> > >> Hi > >> > >> As PR90106 (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90106), > >> when gcc meets builtin function call like: > >> > >> y = sqrt (x); > >> > >> The cdce pass tries to transform the call into an internal function > >> call and conditionally executes call with a simple range check on the > >> arguments which can detect most cases and the errno does not need > >> to be set. It looks like: > >> > >> y = IFN_SQRT (x); > >> if (__builtin_isless (x, 0)) > >> sqrt (x); > >> > >> However, If the call is in tail position, for example: > >> > >> y = sqrt (x); > >> return y; > >> > >> will become: > >> > >> y = IFN_SQRT (x); > >> if (__builtin_isless (x, 0)) > >> sqrt (x); > >> return y; > >> > >> This transformation breaks tailcall pattern, and prevents > >> later tailcall optimizations. > >> > >> So This patch transform builtin call with return value into > >> if-then-else part, which looks like: > >> > >> y = sqrt (x); > >> ==> > >> if (__builtin_isless (x, 0)) > >> y = sqrt (x); > >> else > >> y = IFN_SQRT (x); > >> > >> BTW, y = sqrt (x) can also transform like: > >> > >> y = IFN_SQRT (x); > >> if (__builtin_isless (x, 0)) > >> y = sqrt (x); > >> > >> We don‘t choose this pattern because it emits worse assemble > >> code(more move instruction and use more registers) in x86_64. > >> > >> Bootstrapped/regtested on x86_64-linux, ok for trunk? > > > > OK. > JunMa -- do you have a copyright assignment on file and write access to > the repository? If not we should take care of that before proceeding > further. Hi Jeff, Thanks very much for helping. Yes, he is under Alibaba's copyright assignment. What else should we do other than noticing in this mailing list message? BTW, I think JunMa needs to apply write-access though.
Thanks, bin > > Jeff
