[Bug rtl-optimization/95493] [10/11 Regression] test for vector members apparently reordered with assignment to vector members since r10-7523-gb90061c6ec090c6b

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95493

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |rguenth at gcc dot gnu.org

--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> ---
OK, so the issue is we're getting these MEM_ATTRs when expanding the base
as

(mem/c:V4SI (plus:DI (reg/f:DI 77 virtual-stack-vars)
        (const_int -32 [0xffffffffffffffe0])) [5 MEM[(struct ._anon_0 *)_42]+0
S16 A128])

and set_mem_attributes_minus_bitpos due to the variable array-ref wouldn't
assign any here but inherits the already set ones.

  /* Default values from pre-existing memory attributes if present.  */
  refattrs = MEM_ATTRS (ref);
  if (refattrs)
    {
      /* ??? Can this ever happen?  Calling this routine on a MEM that
         already carries memory attributes should probably be invalid.  */
      attrs.expr = refattrs->expr;
      attrs.offset_known_p = refattrs->offset_known_p;
      attrs.offset = refattrs->offset;
      attrs.size_known_p = refattrs->size_known_p;
      attrs.size = refattrs->size;
      attrs.align = refattrs->align;
    }

so the following fixes the issue, the MEM_ATTRs are not what the code
expects them to be set with otherwise.  Because clearly offset_known_p
should be false.

diff --git a/gcc/emit-rtl.c b/gcc/emit-rtl.c
index 2b790636366..0a72269e2ce 100644
--- a/gcc/emit-rtl.c
+++ b/gcc/emit-rtl.c
@@ -2114,6 +2114,10 @@ set_mem_attributes_minus_bitpos (rtx ref, tree t, int
objectp,
            }
          while (TREE_CODE (t2) == ARRAY_REF);

+         attrs.expr = NULL_TREE;
+         attrs.offset_known_p = false;
+         attrs.offset = 0;
+         apply_bitpos = 0;
          if (DECL_P (t2)
              || (TREE_CODE (t2) == COMPONENT_REF
                  /* For trailing arrays t2 doesn't have a size that