https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97005
--- Comment #9 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Tom de Vries <vr...@gcc.gnu.org>: https://gcc.gnu.org/g:5b2d679bbbcc2b976c6e228ba63afdf67c33164e commit r12-7170-g5b2d679bbbcc2b976c6e228ba63afdf67c33164e Author: Tom de Vries <tdevr...@suse.de> Date: Mon Feb 7 14:12:34 2022 +0100 [nvptx] Workaround sub.u16 driver JIT bug There's a nvidia driver JIT bug that mishandles this code (minimized from builtin-arith-overflow-15.c): ... int main (void) { signed char r; unsigned char y = (unsigned char) 0x80; if (__builtin_sub_overflow ((unsigned char)0, (unsigned char)y, &r)) __builtin_abort (); return 0; } ... which at ptx level minimizes to: ... mov.u16 r22, 0x0080; st.local.u16 [frame_var],r22; ld.local.u16 r32,[frame_var]; sub.u16 r33,0x0000,r32; cvt.u32.u16 r35,r33; ... where we expect r35 == 0x0000ff80 but get instead 0xffffff80, and where using nvptx-none-run -O0 fixes the problem. [ See also https://github.com/vries/nvidia-bugs/tree/master/builtin-arith-overflow-15 . ] Try to workaround the bug by using sub.s16 instead of sub.u16. Tested on nvptx. gcc/ChangeLog: 2022-02-07 Tom de Vries <tdevr...@suse.de> PR target/97005 * config/nvptx/nvptx.md (define_insn "sub<mode>3"): Workaround driver JIT bug by using sub.s16 instead of sub.u16.
