[committed,nvptx] Workaround sub.u16 driver JIT bug
Commit Message
Hi,
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.
Committed to trunk.
Thanks,
- Tom
[nvptx] Workaround sub.u16 driver JIT bug
gcc/ChangeLog:
2022-02-07 Tom de Vries <tdevries@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.
---
gcc/config/nvptx/nvptx.md | 9 ++++++++-
1 file changed, 8 insertions(+), 1 deletion(-)
@@ -506,7 +506,14 @@ (define_insn "sub<mode>3"
(minus:HSDIM (match_operand:HSDIM 1 "nvptx_register_operand" "R")
(match_operand:HSDIM 2 "nvptx_register_operand" "R")))]
""
- "%.\\tsub%t0\\t%0, %1, %2;")
+ {
+ if (GET_MODE (operands[0]) == HImode)
+ /* Workaround https://developer.nvidia.com/nvidia_bug/3527713.
+ See PR97005. */
+ return "%.\\tsub.s16\\t%0, %1, %2;";
+
+ return "%.\\tsub%t0\\t%0, %1, %2;";
+ })
(define_insn "mul<mode>3"
[(set (match_operand:HSDIM 0 "nvptx_register_operand" "=R")