https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92294
--- Comment #10 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Richard Sandiford <rsand...@gcc.gnu.org>: https://gcc.gnu.org/g:6a2a38620cf178b53b217051f32d1d7bbba86fc9 commit r11-6796-g6a2a38620cf178b53b217051f32d1d7bbba86fc9 Author: Richard Sandiford <richard.sandif...@arm.com> Date: Tue Jan 19 17:50:53 2021 +0000 alias: Fix offset checks involving section anchors [PR92294] memrefs_conflict_p assumes that: [XB + XO, XB + XO + XS) does not alias [YB + YO, YB + YO + YS) whenever: [XO, XO + XS) does not intersect [YO, YO + YS) In other words, the accesses can alias only if XB == YB at runtime. However, this doesn't cope correctly with section anchors. For example, if XB is an anchor symbol and YB is at offset XO from the anchor, then: [XB + XO, XB + XO + XS) overlaps [YB, YB + YS) whatever the value of XO is. In other words, when doing the alias check for two symbols whose local definitions are in the same block, we should apply the known difference between their block offsets to the intersection test above. gcc/ PR rtl-optimization/92294 * alias.c (compare_base_symbol_refs): Take an extra parameter and add the distance between two symbols to it. Enshrine in comments that -1 means "either 0 or 1, but we can't tell which at compile time". (memrefs_conflict_p): Update call accordingly. (rtx_equal_for_memref_p): Likewise. Take the distance between symbols into account.
