https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108599
--- Comment #8 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:963315a922e228c4f6853826666151fc540f111a commit r13-5529-g963315a922e228c4f6853826666151fc540f111a Author: Jakub Jelinek <ja...@redhat.com> Date: Tue Jan 31 10:12:19 2023 +0100 i386: Fix up ix86_convert_const_wide_int_to_broadcast [PR108599] The following testcase is miscompiled. The problem is that during RTL DSE we see a V4DI register is being loaded { 16, 16, 0, 0 } value and DSE mostly works in terms of scalar modes, so it calls movoi to set an OImode REG to (const_wide_int 0x100000000000000010) and ix86_convert_const_wide_int_to_broadcast thinks it can compute that value by broadcasting DImode 0x10. While it is true that for TImode result the broadcast could be used, for OImode/XImode it can't be, because all but the lowest 2 HOST_WIDE_INTs aren't present (so are 0 or -1 depending on sign), not 0x10 in this case. The function checks if the least significant HOST_WIDE_INT elt of the CONST_WIDE_INT is broadcastable from QI/HI/SI/DImode and then /* Check if OP can be broadcasted from VAL. */ for (int i = 1; i < CONST_WIDE_INT_NUNITS (op); i++) if (val != CONST_WIDE_INT_ELT (op, i)) return nullptr; That is needed of course, but nothing checks that CONST_WIDE_INT_NUNITS (op) isn't too small for the mode in question. I think if op would be 0 or -1, it ought to be never CONST_WIDE_INT, but CONST_INT and so we can just punt whenever the number of CONST_WIDE_INT elts is not the expected one. 2023-01-31 Jakub Jelinek <ja...@redhat.com> PR target/108599 * config/i386/i386-expand.cc (ix86_convert_const_wide_int_to_broadcast): Return nullptr if CONST_WIDE_INT_NUNITS (op) times HOST_BITS_PER_WIDE_INT isn't equal to bitsize of mode. * gcc.target/i386/avx2-pr108599.c: New test.
