https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95690
--- Comment #6 from CVS Commits <cvs-commit at gcc dot gnu.org> --- The releases/gcc-10 branch has been updated by Richard Biener <rgue...@gcc.gnu.org>: https://gcc.gnu.org/g:7d919c33fbd29a996326840dae3b5e093c3190f4 commit r10-8355-g7d919c33fbd29a996326840dae3b5e093c3190f4 Author: Richard Biener <rguent...@suse.de> Date: Thu Jun 4 13:44:58 2020 +0200 middle-end/95493 - bogus MEM_ATTRS for variable array access The following patch avoids keeping the inherited MEM_ATTRS when set_mem_attributes_minus_bitpos is called with a variable ARRAY_REF. The inherited ones may not reflect the correct offset and neither does the updated alias-set match the inherited MEM_EXPR. This all ends up confusing path-based alias-analysis, causing wrong-code. The fix is to stop not adopting a MEM_EXPR for certain kinds of expressions and instead handle everything we can. There's still the constant kind trees case which I'm too lazy to look into right now. I did refrain from adding SSA_NAME there and instead avoided calling set_mem_attributes_minus_bitpos when debug expression expansion ended up expanding a SSA definition RHS which should already have taken care of setting the appropriate MEM_ATTRS. It also avoids calling set_mem_attributes on the DECL_INITIAL of a CONST_DECL which seems pointless since there cannot be a sensible MEM_EXPR derived from that. We're overwriting both other possibly useful info, alias-set and alignment immediately so the following patch simply removes the call instead of making the function deal with even more (unexpected) trees that are not memory accesses. 2020-06-23 Richard Biener <rguent...@suse.de> PR middle-end/95493 PR middle-end/95690 * cfgexpand.c (expand_debug_expr): Avoid calling set_mem_attributes_minus_bitpos when we were expanding an SSA name. * emit-rtl.c (set_mem_attributes_minus_bitpos): Remove ARRAY_REF special-casing, add CONSTRUCTOR to the set of special-cases we do not want MEM_EXPRs for. Assert we end up with reasonable MEM_EXPRs. * varasm.c (build_constant_desc): Remove set_mem_attributes call. * g++.dg/torture/pr95493.C: New testcase. * g++.dg/torture/pr95493-1.C: Likewise. * gfortran.dg/pr95690.f90: Likewise.
