Hi All,
Below is the patterns defined for the mov and add instruction
.
[(set (match_operand:HI 0 "general_mov_operand" "=r,rRA")
(match_operand:HI 1 "general_mov_operand" "rRAi,ri"))]
""
{
}
)
(define_insn "addhi3"
[(set (match_operand:HI 0 "register_operand" "=Ar")
(plus:HI (match_operand:HI 1 "register_operand" "%0")
(match_operand:HI 2 "general_mov_operand" "Ar")))]
""
"add\t%0, (%2)"
)
The problem we stuck with is that the compiler emit unoptimal code for
the below testcase with -O0 option
int a,b;
int func()
{
return a=b;
}
.s file
ld BC, (a)
ld WA, (b)
add WA, BC
ld (a), WA
ret
the compiler try to load a and b to the register BC and WA
respectively in the expand_assignment and add them , then store back
the result to a.
But if you see the addhi3 definition ,it states that i'm allowed to
emit instruction like
add WA,(a)
where second operand can be register indirect addressing .
I can write peephole pattern to optimize the emitted code like
.s file
ld WA, (b)
add WA, (a)
ld (a), WA
ret
the reason for the unoptimal code is that the code is expanded to
load the memory contents to the registers and then update the add
operands accordingly. I don't want this to happen .
I will be glad ,if somebody from the group share their experience or
through some insights how i can achieve this .
Thanks
~Umesh
