https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112809
--- Comment #3 from GCC 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:0ca64f846edce3c7b7f26bcc5978118e560e65b1 commit r14-6209-g0ca64f846edce3c7b7f26bcc5978118e560e65b1 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Dec 6 09:55:30 2023 +0100 lower-bitint: Fix arithmetics followed by extension by many bits [PR112809] A zero or sign extension from result of some upwards_2limb operation is implemented in lower_mergeable_stmt as an extra loop which fills in the extra bits with 0s or 1s. If the delta of extended vs. unextended bit count is small, the code doesn't use a loop and emits up to a couple of stores to constant indexes, but if the delta is large, it uses cnt = (bo_bit != 0) + 1 + (rem != 0); statements. bo_bit is non-zero for bit-field loads and is done in that case as straight line, the unconditional 1 in there is for a loop which handles most of the limbs in the delta and finally (rem != 0) is for the case when the extended precision is not a multiple of limb_prec and is again done in straight line code (after the loop). The testcase ICEs because the decision what idx to use was incorrect for kind == bitint_prec_huge (i.e. when the precision delta is very large) and rem == 0 (i.e. the extended precision is multiple of limb_prec). In that case cnt is either 1 (if bo_bit == 0) or 2, and idx should be either first size_int (start) and then result of create_loop (for bo_bit != 0) or just result of create_loop, but by mistake the last case was size_int (end), which means when precision is multiple of limb_prec storing above the precision (which ICEs; but also not emitting the loop which is needed). 2023-12-06 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/112809 * gimple-lower-bitint.cc (bitint_large_huge::lower_mergeable_stmt): For separate_ext in kind == bitint_prec_huge mode if rem == 0, create for i == cnt - 1 the loop rather than using size_int (end). * gcc.dg/bitint-48.c: New test.
