How to optimize load and stores? - optimization

Question

I'm trying to have a bunch of operation executed on different targets such as ARM,Bfin... but every time I write a simple code in C and then compile it for each operation it has like 2 loads and one store which is unnecessary for every operation.
ldr r2, [fp, #-24]
ldr r3, [fp, #-28]
add r3, r2, r3
str r3, [fp, #-20]
ldr r2, [fp, #-36]
ldr r3, [fp, #-40]
add r3, r2, r3
str r3, [fp, #-32]
ldr r2, [fp, #-44]
ldr r3, [fp, #-48]
add r3, r2, r3
str r3, [fp, #-20]
ldr r3, [fp, #-16]
add r3, r3, #1
str r3, [fp, #-16]
When I turn on any optimization options, even -O1, it simply calculates the result and stores it in the output:
subl $24, %esp
movl $4, 4(%esp)
movl $.LC0, (%esp)
Is there anyway,I can have operations without fetching the same variable over and over again? I've tried gcc -fgcse-lm and -fgcse-sm but that didn't work.

Answer 1

It depends on the operation. Gcc can't figure out a high level optimizations for
int a(int b, int c)
{
b-=c;
c-=b;
b-=c;
c-=b;
b-=c;
c-=b;
return c;
}

Answer 2

If you want to do benchmarking and avoid constant folding and dead code elimination of the optimizer in gcc, you need to use non-constants as input and make sure the result goes somewhere.
For instance, instead of using
int main(int argc, char** argv) {
int a = 1;
int b = 2;
start_clock();
int c = a + b;
int d = c + a;
int e = d + b;
stop_clock();
output_time_needed();
return 0;
}
You should use something like
int main(int argc, char** argv) {
int a = argc;
int b = argc + 1;
start_clock();
int c = a + b;
int d = c + a;
int e = d + b;
stop_clock();
output_time_needed();
return e;
}