> -O3 enables function inlining. With function inlining, we can see that > the arrays are unused and we optimize them away. Without the arrays, > the stack frames are small, and hence you get small offsets.
The external functions in my example using the arrays ensures that the arrays are not optimized away. > FRAME_GROWS_DOWNWARD has little effect on frame offsets. The registers that are spilled are allocated place in the stack frame last, so when FRAME_GROWS_DOWNWARD, the displacement offsets are smaller for spilled registers than with the stack frame growing upwards. Spilled registeres are accessed more frequently than other entries in the stack frame, so getting this right(which I think pretty much all backends do, after a quick scan) has a significant positive impact on code-size. -- Øyvind Harboe http://www.zylin.com
