[Bug middle-end/57503] [6/7/8 Regression] Expand uses wrong multiply routine

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57503

Georg-Johann Lay <gjl at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|2013-10-07 00:00:00         |2018-1-15
      Known to fail|                            |5.5.0, 6.4.1, 7.2.1

--- Comment #15 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
Confirmed with v5.5, v6.4, v7.2 and current trunk:

With the test case fom comment #8 and

$ avr-gcc -S -Os pr57503.c -mmcu=atmega8 -fdump-rtl-expand && cat pr57503.c
pr57503.c.234r.expand 

long
func1 (unsigned char a, unsigned char b, int c)
{
    unsigned ab = a * b;
    return (long) ab * c;
}

;; Function func1 (func1, funcdef_no=0, decl_uid=1511, cgraph_uid=0,
symbol_order=0)


;; Generating RTL for gimple basic block 2


...

(note 5 4 8 2 NOTE_INSN_FUNCTION_BEG)
(insn 8 5 9 2 (set (reg:HI 48)
        (mult:HI (zero_extend:HI (reg/v:QI 44 [ a ]))
            (zero_extend:HI (reg/v:QI 45 [ b ])))) "pr57503.c":4 -1
     (nil))
(insn 9 8 10 2 (parallel [
            (set (reg:SI 47)
                (mult:SI (sign_extend:SI (reg:HI 48))
                    (sign_extend:SI (reg/v:HI 46 [ c ]))))
            (clobber (reg:HI 26 r26))
            (clobber (reg:DI 18 r18))
        ]) "pr57503.c":5 -1
     (nil))

Hence in the 1st MULT the operands are correctly zero-extended, but in the 2nd
one there is still the wrong sign_extend:SI (reg:HI 48).