https://gcc.gnu.org/bugzilla/show_bug.cgi?id=104237
--- Comment #11 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-11 branch has been updated by Jakub Jelinek <ja...@gcc.gnu.org>: https://gcc.gnu.org/g:88ff2eb5cc2c1af2ae751c02997d0b5667662782 commit r11-9594-g88ff2eb5cc2c1af2ae751c02997d0b5667662782 Author: Jakub Jelinek <ja...@redhat.com> Date: Fri Jan 28 11:48:18 2022 +0100 cfgrtl: Fix up locus comparison in unique_locus_on_edge_between_p [PR104237] The testcase in the PR (not included for the testsuite because we don't have an (easy) way to -fcompare-debug LTO, we'd need 2 compilations/linking, one with -g and one with -g0 and -fdump-rtl-final= at the end of lto1 and compare that) has different code generation for -g vs. -g0. The difference appears during expansion, where we have a goto_locus that is at -O0 compared to the INSN_LOCATION of the previous and next insn across an edge. With -g0 the locations are equal and so no nop is added. With -g the locations aren't equal and so a nop is added holding that location. The reason for the different location is in the way how we stream in locations by lto1. We have lto_location_cache::apply_location_cache that is called with some set of expanded locations, qsorts them, creates location_t's for those and remembers the last expanded location. lto_location_cache::input_location_and_block when read in expanded_location is equal to the last expanded location just reuses the last location_t (or adds/changes/removes LOCATION_BLOCK in it), when it is not queues it for next apply_location_cache. Now, when streaming in -g input, we can see extra locations that don't appear with -g0, and if we are unlucky enough, those can be sorted last during apply_location_cache and affect what locations are used from the single entry cache next. In particular, second apply_location_cache with non-empty loc_cache in the testcase has 14 locations with -g0 and 16 with -g and those 2 extra ones sort both last (they are the same). The last one from -g0 then appears to be input_location_and_block sourced again, for -g0 triggers the single entry cache, while for -g it doesn't and so apply_location_cache will create for it another location_t with the same content. The following patch fixes it by comparing everything we care about the location instead (well, better in addition) to a simple location_t == location_t check. I think we don't care about the sysp flag for debug info... 2022-01-28 Jakub Jelinek <ja...@redhat.com> PR lto/104237 * cfgrtl.c (loc_equal): New function. (unique_locus_on_edge_between_p): Use it. (cherry picked from commit 430dca620fa3d03e53f6771a2b61d3f0ebb73756)
