https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70245
--- Comment #5 from Vladimir Makarov <vmakarov at gcc dot gnu.org> ---
(In reply to Vladimir Makarov from comment #4)
>
> I see in peephole a wrong transformation:
>
> 190: cx:SI=dx:SI
> REG_DEAD dx:SI
> 95: {cx:SI=cx:SI+[cx:SI];clobber flags:CC;}
>
> into
>
> 242: cx:SI=[cx:SI]
> 243: {cx:SI=cx:SI+dx:SI;clobber flags:CC;}
The pattern in question:
(define_peephole2
[(set (match_operand:SI 0 "register_operand")
(match_operand:SI 1 "register_operand"))
(parallel [(set (match_dup 0)
(match_operator:SI 3 "commutative_operator"
[(match_dup 0)
(match_operand:SI 2 "memory_operand")]))
(clobber (reg:CC FLAGS_REG))])]
"REGNO (operands[0]) != REGNO (operands[1])
&& GENERAL_REGNO_P (REGNO (operands[0]))
&& GENERAL_REGNO_P (REGNO (operands[1]))"
[(set (match_dup 0) (match_dup 4))
(parallel [(set (match_dup 0)
(match_op_dup 3 [(match_dup 0) (match_dup 1)]))
(clobber (reg:CC FLAGS_REG))])]
"operands[4] = replace_rtx (operands[2], operands[0], operands[1]);")
