https://gcc.gnu.org/bugzilla/show_bug.cgi?id=118446
--- Comment #4 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Earnshaw <rearn...@gcc.gnu.org>: https://gcc.gnu.org/g:0a339746e7646bacf2c8aa5512268d23660f26f9 commit r16-454-g0a339746e7646bacf2c8aa5512268d23660f26f9 Author: Richard Earnshaw <rearn...@arm.com> Date: Fri Mar 28 12:59:03 2025 +0000 arm: Only reverse FP inequalities when -ffinite-math-only [PR110796...] On Arm we have been failing to fully implement support for IEEE NaNs in inequality comparisons because we have allowed reversing of inequalities in a way that allows SELECT_CC_MODE to produce different answers. For example, the reverse of GT is UNLE, but if we pass these two RTL codes to SELECT_CC_MODE, the former will return CCFPEmode, while the latter CCFPmode. It would be possible to allow fully reversible FPmodes, but to do so would involve adding yet more RTL codes, something like NOT_GT and NOT_UNLE, for the cases we cannot currently reverse. NOT_GT would then have the same condition code generation as UNLT, but the same mode selection as GT. In the mean time, we need to restrict REVERSIBLE_CC_MODE to non-floating modes unless we are compiling with -ffinite-math-only. In that case we can continue to reverse the comparisons, but now we want to always select CCFPmode as there's no need to consider the exception raising cases. PR target/110796 PR target/118446 gcc/ChangeLog: * config/arm/arm.h (REVERSIBLE_CC_MODE): FP modes are only reversible if flag_finite_math_only. * config/arm/arm.cc (arm_select_cc_mode): Return CCFPmode for all FP comparisons if flag_finite_math_only. gcc/testsuite/ChangeLog: * gcc.target/arm/armv8_2-fp16-arith-1.c: Adjust due to no-longer emitting VCMPE when -ffast-math..
