Hi, I'm new in gcc, and maybe misunderstand the constraint modifier '+'.
As the internal document says, '+' means an inout parameter. In my
mind, it means the instruction both reads and writes the pseudo
register.
Assuming I have a pattern like:
(define_insn "lssu"
[(set (match_operand:m1 0 ...)
(unspec:m1 [ (match_operand:SI 1 "register_operand" "+r")
(match_operand:SI 2 ...)] UNSPEC_XXX))]
and I have a sequence of code like
(insn 1 .... (set (reg:SI 100) (...)))
...
(insn 10 ... (set (reg:m1 200) (unspec:m1 [(reg:SI 100) (...)]
UNSPEC_XXX)) 33 {lssu} (nil))
...
(insn 30 ... (set (reg:SI 300) (reg:SI 100)
Can I expect that pseudo reg 100 in insn 30 has the new value written
by insn 10?
My experiments show that this is not true, and pseudo reg 100 in insn
30 still takes the value in insn 1.
Or maybe something else is wrong in our porting ?
--
Thanks.
Handong
