size of code gcc creates (was "m68k-coff-gcc and NOPs")

[Scott A Sumner <sasumner at juno dot com>]

Speaking of being out of prom space, from what I've been able to
determine, gcc is a pig when it comes to code space.

My application is buildable under two toolsets, Fiddes' gcc version 4 and
Mentor Graphics Microtec Research version 4.4.  Here's a comparison of
code (ROM) sizes with the two toolsets:

gcc:  655KB
Microtec:  560KB

As you can see, the code produced by gcc is almost 17% bigger--quite a
disparity!

Anyone have an opinion as to why this is so?





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Scott,

Thanks for your reply. On further investigtion I have found that they
(the nops) are only generated when I use -fomit-frame-pointer and any
level of optimisation, e.g. -Os in my case (as you may have guess I am
short of PROM space). It is still a mystery why.

Regards, Chris

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Chris,

Interesting.  I just generated an assembly source listing from one of my
m68k-coff-gcc-compiled .c files and I don't see any nops after the rts's.
 I wonder why?

Scott

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Does anybody know why the 68K version of gcc compiles a NOP instruction
at the end of each function, after the RTS?                              
                          

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