https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104985
--- Comment #21 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-9 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:5169f5756e26feac7042a6046e974dd4b650b6ed commit r9-10145-g5169f5756e26feac7042a6046e974dd4b650b6ed Author: Jakub Jelinek <ja...@redhat.com> Date: Wed Apr 6 18:42:52 2022 +0200 combine: Don't record for UNDO_MODE pointers into regno_reg_rtx array [PR104985] The testcase in the PR fails under valgrind on mips64 (but only Martin can reproduce, I couldn't). But the problem reported there is that SUBST_MODE remembers addresses into the regno_reg_rtx array, then some splitter needs a new pseudo and calls gen_reg_rtx, which reallocates the regno_reg_rtx array and finally undo operation is done and dereferences the old regno_reg_rtx entry. The rtx values stored in regno_reg_rtx array seems to be created by gen_reg_rtx only and since then aren't modified, all we do for it is adjusting its fields (e.g. adjust_reg_mode that SUBST_MODE does). So, I think it is useless to use where.r for UNDO_MODE and store ®no_reg_rtx[regno] in struct undo, we can store just regno_reg_rtx[regno] (i.e. pointer to the REG itself instead of pointer to pointer to REG) or could also store just the regno. The following patch does the latter, and because SUBST_MODE no longer needs to be a macro, changes all SUBST_MODE uses to subst_mode. 2022-04-06 Jakub Jelinek <ja...@redhat.com> PR rtl-optimization/104985 * combine.c (struct undo): Add where.regno member. (do_SUBST_MODE): Rename to ... (subst_mode): ... this. Change first argument from rtx * into int, operate on regno_reg_rtx[regno] and save regno into where.regno. (SUBST_MODE): Remove. (try_combine): Use subst_mode instead of SUBST_MODE, change first argument from regno_reg_rtx[whatever] to whatever. For UNDO_MODE, use regno_reg_rtx[undo->where.regno] instead of *undo->where.r. (undo_to_marker): For UNDO_MODE, use regno_reg_rtx[undo->where.regno] instead of *undo->where.r. (simplify_set): Use subst_mode instead of SUBST_MODE, change first argument from regno_reg_rtx[whatever] to whatever. (cherry picked from commit 61bee6aed26eb30b798c75b9a595c9d51e080442)
