[Bug target/112778] ICE in ppc64-linux-gnu crosscompiler in store_by_pieces since r14-5946-g1ff6d9f7428b06

[linkw at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112778

Kewen Lin <linkw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |aoliva at gcc dot gnu.org,
                   |                            |bergner at gcc dot gnu.org,
                   |                            |linkw at gcc dot gnu.org,
                   |                            |segher at gcc dot gnu.org
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |NEW
            Summary|ICE in ppc64-linux-gnu      |ICE in ppc64-linux-gnu
                   |crosscompiler in            |crosscompiler in
                   |store_by_pieces, at         |store_by_pieces since
                   |expr.cc:1820                |r14-5946-g1ff6d9f7428b06
           Keywords|needs-bisection             |
   Last reconfirmed|                            |2023-12-01

--- Comment #1 from Kewen Lin <linkw at gcc dot gnu.org> ---
Confirmed, thanks for reporting, it starts from r14-5946-g1ff6d9f7428b06.

It looks function try_store_by_multiple_pieces has the wrong assumption. For
the code "memset (buf, 'v', 3)", it checks 

+          if (max_bits < orig_max_bits
+              && xlenest + blksize >= xlenest
+              && can_store_by_pieces (xlenest + blksize,
+                                      builtin_memset_read_str,
+                                      &valc, align, true))

, succeeds and breaks. later it goes with blksize:

      to = store_by_pieces (to, blksize,
                            constfun, constfundata,
                            align, true,
                            max_len != 0 ? RETURN_END : RETURN_BEGIN);

and fails at targetm.use_by_pieces_infrastructure_p assertion.

It's concluded that can_store_by_pieces (xlenest + blksize, ...) doesn't
necessarily means can_store_by_pieces (blksize, ...).