https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112941
--- Comment #7 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:be9e8de628471399ee5abb1e6ba7738139256b67 commit r14-6742-gbe9e8de628471399ee5abb1e6ba7738139256b67 Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Dec 20 11:32:52 2023 +0100 lower-bitint: Fix up handling of nested casts in mergeable stmt handling [PR112941] The following patch fixes 2 issues in handling of casts for mergeable stmts. The first hunk fixes the case when we have two nested casts (typically after optimization that is zero-extension of a sign-extension because everything else should have been folded into a single cast). If the lowering of the outer cast needs to make the code conditional (e.g. for (...) { if (idx <= 32) { if (idx < 32) { ... handle_operand (idx); ... } else { ... handle_operand (32); ... } } ... } ) and the lowering of the inner one as well, right now it creates invalid SSA form, because even for the inner cast we need a PHI on the loop and the PHI argument from the latch edge is a SSA_NAME initialized in the conditionally executed bb. The hunk fixes that by detecting such a case and adding further PHI nodes at the end of the ifs such that the right value propagates to the next loop iteration. We can use 0 arguments for the other edges because the inner operand handling is only done for the first set of iterations and then the other ifs take over. The rest fixes a case of again invalid SSA form, when for a sign extension we need to use the 0 or -1 value initialized by earlier iteration in a constant idx case, the code was using the value of the loop PHI argument from latch edge rather than result; that is correct for cases expanded in straight line code after the loop, but not inside of the loop for the cases of handle_cast conditionals, there we should use PHI result. This is done in the second hunk and supported by the remaining hunks, where it clears m_bb to tell the code we aren't in the loop anymore. Note, this patch doesn't deal with similar problems during multiplication, division, floating casts etc. where we just emit a library call. I'll need to make sure in that case we don't merge more than one cast per operand. 2023-12-20 Jakub Jelinek <ja...@redhat.com> PR tree-optimization/112941 * gimple-lower-bitint.cc (bitint_large_huge::handle_cast): If save_cast_conditional, instead of adding assignment of t4 to m_data[save_data_cnt + 1] before m_gsi, add phi nodes such that t4 propagates to m_bb loop. For constant idx, use m_data[save_data_cnt] rather than m_data[save_data_cnt + 1] if inside of the m_bb loop. (bitint_large_huge::lower_mergeable_stmt): Clear m_bb when no longer expanding inside of that loop. (bitint_large_huge::lower_comparison_stmt): Likewise. (bitint_large_huge::lower_addsub_overflow): Likewise. (bitint_large_huge::lower_mul_overflow): Likewise. (bitint_large_huge::lower_bit_query): Likewise. * gcc.dg/bitint-55.c: New test.
