------- Comment #4 from ubizjak at gmail dot com 2009-01-01 17:35 -------
(In reply to comment #3)
> Most likely addsi3_carry should accept 0 as one of the operands.
It does:
(define_insn "addsi3_carry"
[(set (match_operand:SI 0 "nonimmediate_operand" "=rm,r")
(plus:SI (plus:SI (match_operand:SI 3 "ix86_carry_flag_operator" "")
(match_operand:SI 1 "nonimmediate_operand" "%0,0"))
(match_operand:SI 2 "general_operand" "ri,rm")))
(clobber (reg:CC FLAGS_REG))]
It looks to me that cprop_hardreg is the pass to handle this case, at least
this sequence should be handled (to propagate cx):
(insn 74 50 52 3 pr33717.c:12 (parallel [
(set (reg:SI 2 cx [+4 ])
(const_int 0 [0x0]))
(clobber (reg:CC 17 flags))
]) 45 {*movsi_xor} (nil))
(insn 53 52 54 3 pr33717.c:12 (parallel [
(set (reg:SI 4 si [+4 ])
(plus:SI (plus:SI (ltu:SI (reg:CC 17 flags)
(const_int 0 [0x0]))
(reg:SI 4 si [+4 ]))
(reg:SI 2 cx [+4 ])))
(clobber (reg:CC 17 flags))
]) 266 {addsi3_carry} (expr_list:REG_DEAD (reg:CC 17 flags)
(expr_list:REG_DEAD (reg:SI 2 cx [+4 ])
(expr_list:REG_UNUSED (reg:CC 17 flags)
(nil)))))
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33717
