[Bug middle-end/33348] [4.3 Regression] gfortran.dg/g77/19990826-3.f fails at -O1

["hubicka at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from hubicka at gcc dot gnu dot org  2007-09-16 21:52 -------
What happens in this testcase is (mis)behaviour of invariant code motion.
On instruction:
(set (mem/c/i:SI (plus:DI (reg/f:DI 113 sfp)
            (const_int 80 [0x50])) [3 S4 A32])
    (fix:SI (reg:DF 135)))

the invariant code is trying to replace the write->load pair, however the
truncsfdf2 expander is expanding fix from reg to reg will offload the value to
memory again, so we are replacing load by:

(insn 44 0 45 (parallel [
            (set (mem/c/i:SI (plus:DI (reg/f:DI 113 sfp)
                        (const_int 84 [0x54])) [3 S4 A32])
                (fix:SI (reg:DF 135)))
            (clobber (reg:DI 138))
        ]) -1 (nil))

(insn 45 44 46 (set (reg:SI 137)
        (mem/c/i:SI (plus:DI (reg/f:DI 113 sfp)
                (const_int 84 [0x54])) [3 S4 A32])) -1 (expr_list:REG_EQUAL
(fix:SI (reg:DF 135))
        (nil)))

(insn 46 45 0 (set (reg:SI 136)
        (reg:SI 137)) -1 (nil))

This is not very sane transformation at all IMO.  Zdenek, perhaps we can
disable the transform, when force_operand produces a memory load or some
similar lame trick?

Anyway, the sharing problem is cured by:
Index: loop-invariant.c
===================================================================
*** loop-invariant.c    (revision 128492)
--- loop-invariant.c    (working copy)
*************** move_invariant_reg (struct loop *loop, u
*** 1243,1248 ****
--- 1243,1249 ----
          if (op != reg)
            emit_move_insn (reg, op);
          seq = get_insns ();
+         unshare_all_rtl_in_chain (seq);
          end_sequence ();

          if (!seq_insns_valid_p (seq))

I will commit as obvious if testing passes. Still I would hope we can also
avoid loop from doing this transform at all.

Honza


-- 

hubicka at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |rakdver at gcc dot gnu dot
                   |dot org                     |org
             Status|UNCONFIRMED                 |ASSIGNED
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2007-09-16 21:52:08
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33348