Hi,
I am a beginner on gcc backend. I was performing some experiments
on .md file using a completly new backend set of files written by me. I
end up on something I really could not understand. Regarding addition, I
put the following code on my .md file:
(define_expand "addhi3"
[(set (match_operand:HI 0 "nonimmediate_operand" "")
(plus:HI (match_operand 1 "general_operand" "")
(match_operand 2 "general_operand" "")
)
)
]
""
""
)
(define_insn "*addhi3_2"
[(set (match_operand:HI 0 "nonimmediate_operand" "=r,r,d")
(plus:HI (match_operand:HI 1 "register_operand" "r,r,0")
(match_operand:HI 2 "nonmemory_operand" "r,K,K")
)
)]
""
"@
add \\t%0, %1, %2
add \\t%0, %1, #%c2
add \\t%0, #%c2"
)
Using this code, gcc gives the following error only when I use -O1
(for -O0, -O2 it works OK!):
(insn 16 14 17 0 (set (reg:HI 12)
(plus:HI (mem/i:HI (symbol_ref:HI ("b") <var_decl 0x7fdad4a0
b>) [0 b+0 S2 A16])
(mem/i:HI (symbol_ref:HI ("a") [flags 0x2] <var_decl
0x7fdad430 a>) [0 a+0 S2 A16]))) -1 (nil)
(nil))
I understood that gcc would like to have a insn which accepts "reg =
mem + mem", but I really can not understand why gcc works OK with -O2
and with -O0, but not with -O1.
thank you!
Alex Prado
