Re: object code vs. assembler code

John_Burton@gec-epl.co.uk writes:
>Obviously it is possible for a compiler to produce object code directly
>which seems to be the standard on many other systems which seems much more
>efficent to me.


>[Mostly it's a matter of taste. Some Unix assemblers, particularly the
>earlier ones, were very fast, so there needn't be a performance issue. -John]


Here are some real numbers to play with:


I ran the various stages of gcc-1.40 on 39 source files (about 7000 lines
of code) and timed each stage. These tests were run on a diskless Sun ELC
w/24M running 4.1.1.


Program User+Sys Total


cccp 2.4+6.8 == 9.2


cc1 25.4+6.5 == 31.9


/bin/as 5.0+6.3 == 11.3


So, assembly takes up about 20% of the total time. That's not
insignificant.


If you run a compiler with a faster code generator (such as lcc), then the
middle stage should be smaller by about a factor of 2 or 3, so assembly
can be as much as a quarter or a third of the total execution time.


(So why emit assembler? One of my long-term projects is to write a code
generator for lcc to use SPARC without register windows. I will initially
generate assembler, because it's the quickest way to get code working
(mainly because it's easy to debug). Eventually I would like to think
about generating object code directly, particularly if I try to
investigate some ideas related to linking (incremental linking, global
pointer..) where a new object format might be called for. I am
structuring the code so that switching from one to the other will require
a trivial amount of work.)


Byron Rakitzis.
--

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