https://gcc.gnu.org/bugzilla/show_bug.cgi?id=121652
--- Comment #23 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jeff Law <[email protected]>: https://gcc.gnu.org/g:60c6f92fb192352d784ab3153a9e11c19a3216a0 commit r16-4191-g60c6f92fb192352d784ab3153a9e11c19a3216a0 Author: Aurelien Jarno <[email protected]> Date: Thu Oct 2 09:05:34 2025 -0600 [PATCH v2] RISC-V: fix __builtin_round NaN handling [PR target/121652] __builtin_round() fails to correctly generate invalid exceptions for NaN inputs when -ftrapping-math is used (which is the default). According to the specification, an invalid exception should be raised for sNaN, but not for qNaN. Commit f12a27216952 ("RISC-V: fix __builtin_round clobbering FP...") attempted to avoid raising an invalid exception for qNaN by saving and restoring the FP exception flags. However this inadvertently suppressed the invalid exception for sNaN as well. Instead of saving/restoring fflags, this patch uses the same approach than the well tested GLIBC round implementation. When flag_trapping_math is enabled, it first checks whether the input is a NaN using feq.s/d. In that case it adds the input value with itself to possibly convert sNaN into qNaN. With this change, the glibc testsuite passes again. The generated code with -ftrapping-math now looks like: convert_float_to_float_round feq.s a5,fa0,fa0 beqz a5,.L6 auipc a5,0x0 flw fa4,42(a5) fabs.s fa5,fa0 flt.s a5,fa5,fa4 beqz a5,.L5 fcvt.w.s a5,fa0,rmm fcvt.s.w fa5,a5 fsgnj.s fa0,fa5,fa0 ret .L6: fadd.s fa0,fa0,fa0 .L5: ret With -fno-trapping-math, the additional checks are omitted so the resulting code is unchanged. In addition this fixes the following failures: FAIL: gcc.target/riscv/rvv/autovec/vls/math-nearbyint-1.c -O3 -ftree-vectorize -mrvv-vector-bits=scalable scan-assembler-times frflags\\s+[atx][0-9]+ 32 FAIL: gcc.target/riscv/rvv/autovec/vls/math-nearbyint-1.c -O3 -ftree-vectorize -mrvv-vector-bits=scalable scan-assembler-times fsflags\\s+[atx][0-9]+ 32 Fixes: f652a35877e3 ("This is almost exclusively Jivan's work....") Fixes: f12a27216952 ("RISC-V: fix __builtin_round clobbering FP...") PR target/121652 gcc/ChangeLog: * config/riscv/riscv.md (round_pattern): special case NaN input instead of saving/restoring fflags. gcc/testsuite/ChangeLog: * gcc.target/riscv/rvv/autovec/vls/math-nearbyint-1.c: Adjust scan pattern for fewer instances of frflags/fsrflags.
