https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94516
--- Comment #10 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:70b55b25aa14b60f0e0f0193f7178bae756076ad commit r10-7617-g70b55b25aa14b60f0e0f0193f7178bae756076ad Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Apr 8 12:04:46 2020 +0200 postreload: Fix autoinc handling in reload_cse_move2add [PR94516] The following testcase shows two separate issues caused by the cselib changes. One is that through the cselib sp tracking improvements on ... r12 = rsp; rsp -= 8; push cst1; push cst2; push cst3; call rsp += 32; rsp -= 8; push cst4; push cst5; push cst6; call rsp += 32; rsp -= 8; push cst7; push cst8; push cst9; call rsp += 32 reload_cse_simplify_set decides to optimize the rsp += 32 insns into rsp = r12 because cselib figures that the r12 register holds the right value. From the pure cost perspective that seems like a win and on its own at least for -Os that would be beneficial, except that there are those rsp -= 8 stack adjustments after it, where rsp += 32; rsp -= 8; is optimized into rsp += 24; by the csa pass, but rsp = r12; rsp -= 8 can't. Dunno what to do about this part, the PR has a hack in a comment. Anyway, the following patch fixes the other part, which isn't a missed optimization, but a wrong-code issue. The problem is that the pushes of constant are on x86 represented through PRE_MODIFY and while move2add_note_store has some code to handle {PRE,POST}_{INC,DEC} without REG_INC note, it doesn't handle {PRE,POST}_MODIFY (that would be enough to fix this testcase). But additionally it looks misplaced, because move2add_note_store is only called on the rtxes that are stored into, while RTX_AUTOINC can happen not just in those, but anywhere else in the instruction (e.g. pop insn can have autoinc in the SET_SRC MEM). REG_INC note seems to be required for any autoinc except for stack pointer autoinc which doesn't have those notes, so this patch just handles the sp autoinc after the REG_INC note handling loop. 2020-04-08 Jakub Jelinek <ja...@redhat.com> PR rtl-optimization/94516 * postreload.c: Include rtl-iter.h. (reload_cse_move2add): Handle SP autoinc here by FOR_EACH_SUBRTX_VAR looking for all MEMs with RTX_AUTOINC operand. (move2add_note_store): Remove {PRE,POST}_{INC,DEC} handling. * gcc.dg/torture/pr94516.c: New test.
