On Mon, Jan 12, 2015 at 05:30:46PM +0000, Andrew Pinski wrote: > On Mon, Jan 12, 2015 at 7:52 AM, Kyrill Tkachov <kyrylo.tkac...@arm.com> > wrote: > > Hi all, > > > > As raised in https://gcc.gnu.org/ml/gcc-patches/2014-12/msg01237.html and > > discussed in that thread, using __builtin_sqrt for vsqrt_f64 may end up in a > > call to the library sqrt at -O0. To avoid that this patch uses a target > > builtin for sqrt on DF mode and uses that to implement the intrinsic. > > > > With this patch I don't see sqrt calls being created at -O0 on a large > > arm_neon.h testcase where they were generated before. > > aarch64-none-elf testing and the intrinsics testsuite in particular are > > clean. > > Ok for trunk? > > Maybe have a target fold which folds this into sqrt if -fno-math-errno > is supplied. This might be useful the -ffast-math case. > Maybe also fold it when a constant is supplied too.
Given that we are now in Stage 4, I'd rather see this fixed for GCC 5.0 in the way Kyrill proposed than languishing on a TODO list. Though an IOU ticket on bugzilla for the missed optimization seems a good idea to me. Unless Kyrill already has something in the works to address your comment, this looks like the right short-term solution to me (Though Marcus/Richard will have to approve it). Thanks, James > > 2015-01-12 Kyrylo Tkachov <kyrylo.tkac...@arm.com> > > > > * config/aarch64/aarch64-simd-builtins.def (sqrt): Use BUILTIN_VDQF_DF. > > * config/aarch64/arm_neon.h (vsqrt_f64): Use __builtin_aarch64_sqrtdf > > instead of __builtin_sqrt. >
