Uninitialized register in gcse on VMS

["Douglas B. Rupp" <rupp at gnat dot com>]

Greetings,

I'm chasing a -O2 bug in the bootstrap on Alpha/VMS and I don't know how
to proceed. Please advise.

Doug Rupp
rupp@gnat.com
----------------------------------------------------------------------------

When compiling reload1.c with stage1/cc1 -O2
an uninitialized register (r11) gets stored into &reload_obstack
in the call to obstack_alloc in reload1.c: init_reload().

The dump files show the pseudo register 226 (which eventually becomes r11
in greg) being created in gcse:

09-addressof:
-------------
(insn 495 559 497 (set (reg:SI 212)
        (mem/s:SI (plus:DI (reg/f:DI 160)
                (const_int 12 [0xc])) [11 S4 A32])) 223 {*movsi_nt_vms} (nil)
    (nil))

10-gcse:
--------
(insn 495 559 497 (set (reg:SI 212)
        (reg:SI 226)) 223 {*movsi_nt_vms} (nil)
    (expr_list:REG_EQUAL (mem/s:SI (const:DI (plus:DI (symbol_ref:DI ("reload_obstack"))
                    (const_int 12 [0xc]))) [11 S4 A32])
        (nil)))

Pseudo 226 is nowhere initialized in 10-gcse, nor in any dump file.

Here is the call that creates 226:
----------------------------------
gcse.c: pre_delete(): 4916
  /* Create a pseudo-reg to store the result of reaching
     expressions into.  Get the mode for the new pseudo from
     the mode of the original destination pseudo.  */
  if (expr->reaching_reg == NULL)
    expr->reaching_reg
      = gen_reg_rtx (GET_MODE (SET_DEST (set)));

And the backtrace:
------------------
0 emit-rtl.c:701    gen_reg_rtx
1 gcse.c:4920       pre_delete
2 gcse.c:4999       pre_gcse
3 gcse.c:5045       one_pre_gcse_pass
4 gcse.c:826        gcse_main
5 toplev.c:3080     rest_of_compilation
....

gcc "trunk" sources from 20011030.