Phil Endecott writes: > Hi Priya, > > Priya Narasimhan wrote: > > I am compiling relatively simple C programs using "gcc -S > > -fomit-frame-pointer -mcpu=xscale" on a gumstix (ARM Xscale) processor. I > > noticed that the generated assembly code has additional stuff in, beyond > > what I would typically see in a standard ARM assembly program (e.g., one > > that was generated instead through the ARM Development Suite toolchain). > > > > For instance, I see the following comments in the GNU-generated assembly > > code. What do these signify? > > > > @ zero_extendqisi2 > > @ args =0, pretend =0 (what does pretend mean?) > > @ frame_needed = 0, uses_anonymous_args = 0 (what does uses_anonymous_args > > mean?) > > I don't know, and I suspect that the answer is not very interesting. > The best way to find answers to these questions is probably to study > the gcc source code. > > > Secondly, I notice that without the "-O" option, saving registers to the > > stack happens almost on every alternate line of the generated assembly code. > > What is the purpose of doing this? > > Without -O, gcc runs faster. It can run faster by not spending time > working out what can be stored in registers, and just using the stack > for everything. This is important for debugging: you know that whenever a variable is assigned, the value really is stored in the stack slot associated with that variable. In other words, it's a feature, not a bug. Andrew.
