[Bug optimization/4079] unnecessary register move on simple code

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

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=4079



------- Additional Comments From pinskia at gcc dot gnu dot org  2003-08-29 15:32 -------
Here is more information on how I say this is libcall problem:
(insn 16 12 13 0 (clobber (reg:DI 123)) -1 (nil)
    (insn_list:REG_LIBCALL 17 (nil)))

(insn 13 16 15 0 (set (subreg:SI (reg:DI 123) 4)
        (subreg:SI (reg:DI 122) 0)) 308 {*movsi_internal1} (insn_list 12 (insn_list 16 (nil)))
    (expr_list:REG_DEAD (reg:DI 122)
        (expr_list:REG_NO_CONFLICT (reg:DI 122)
            (nil))))

(insn 15 13 17 0 (set
 (subreg:SI (reg:DI 123) 0)
        (const_i
nt 0 [0x0])) 308
 
{*movsi_internal1} (insn_list 13 (nil))
    (expr_list:REG_NO_CONFLICT (reg:DI 122)
        (nil)))

(insn 17 15 23 0 (set (reg:DI 123)
        (reg:DI 123)) 331 {*movdi_internal32} (insn_list 15 (nil))
    (insn_list:REG_RETVAL 16 (expr_list:REG_EQUAL (lshiftrt:DI (reg:DI 122)
                (const_int 32 [0x20]))
            (nil))))  <--- why is this here, this is causing the problem??


Maybe the fix is to implement (lshiftrt:DI (reg:DI 122) (const_int 32 [0x20])) as an expand 
in the md file.