http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57503
Georg-Johann Lay <gjl at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|WAITING |NEW
--- Comment #8 from Georg-Johann Lay <gjl at gcc dot gnu.org> ---
(In reply to Richard Biener from comment #7)
> Can you please investigate the behavior on current trunk and the top of the
> 4.8 branch?
Using the code from comment #7 the problem persists
$ avr-gcc -S -Os pr57503.c -mmcu=atmega8 -dP
long
func1 (unsigned char a, unsigned char b, int c)
{
unsigned ab = a * b;
return (long) ab * c;
}
The code is a bit different but still wrong:
func1:
; (insn 10 5 25 (set (reg:HI 18 r18 [orig:44 D.1450 ] [44])
; (mult:HI (zero_extend:HI (reg:QI 24 r24 [ a ]))
; (zero_extend:HI (reg/v:QI 22 r22 [orig:50 b ] [50]))))
pr57503.c:4 168 {umulqihi3}
; (expr_list:REG_DEAD (reg:QI 24 r24 [ a ])
; (expr_list:REG_DEAD (reg/v:QI 22 r22 [orig:50 b ] [50])
; (nil))))
mul r24,r22 ; 10 umulqihi3 [length = 3]
movw r18,r0
clr __zero_reg__
; (insn 25 10 26 (set (reg:HI 26 r26)
; (reg/v:HI 20 r20 [orig:51 c ] [51])) pr57503.c:5 82 {*movhi}
; (expr_list:REG_DEAD (reg/v:HI 20 r20 [orig:51 c ] [51])
; (nil)))
movw r26,r20 ; 25 *movhi/1 [length = 1]
; (insn 26 25 21 (set (reg:SI 22 r22)
; (mult:SI (sign_extend:SI (reg:HI 18 r18))
; (sign_extend:SI (reg:HI 26 r26)))) pr57503.c:5 231
{*mulhisi3_call}
; (expr_list:REG_DEAD (reg:HI 26 r26)
; (expr_list:REG_DEAD (reg:HI 18 r18)
; (nil))))
rcall __mulhisi3 ; 26 *mulhisi3_call [length = 1]
; (jump_insn 31 21 30 (return) pr57503.c:6 451 {return}
; (nil)
; -> return)
ret ; 31 return [length = 1]
Insn 26 sign-extends both inputs but R18 (unsigned ab) should be zero-extended.
Tested with SVN 203240
gcc version 4.9.0 20131007 (experimental) (GCC)
