Re: Alternative C compilers on x86_64 Linux?

On 30/09/2016 19:15, Hans-Peter Diettrich wrote:
> BartC schrieb:
>> I seem to remember some comment in this group that tokenising accounts
>> for a big chunk of a compiler's runtime (50% or something).
>
> This seems to be a reasonable figure for C, including all those nasty
> tasks which have to be done before a token can be passed on to the parser.
>
>> While it is true that doing a full compile will take longer than just
>> raw tokenising, should that factor be of the order of 1000 times longer,
>> or three magnitudes?
>
> Find out yourself.


I already know the answer. It /doesn't/ take that much longer.


    Replace the grammar of your tokenizer by the C
> grammar, and test again. I'd wonder if it would not reach the speed of
> your tokenizer. Then add the preprocessor with file inclusion, macro
> definition, recognition and expansion, conditional compilation, and test
> again. Then add Ansi and Unicode string literals and symbol tables, and
> test again.


I don't need to do this work because it's already been done by Tiny C.


Using a monolithic, working test program of 22K lines (25K lines
including standard headers for tcc; 27K using gcc) Tiny C compiled it in
no more than 0.07 seconds (at least 360K lps).


gcc took from 2.2 seconds (unoptimised), to over 8 seconds (optimised).
3-12K lps. (Probably it strained the global optimiser having a large
single module as usually the difference between -O0/-O3 is smaller .)


Tiny C must be parsing the same C grammar and expanding the same macros
as gcc. So whatever it takes to do that, can presumably be done at some
speed faster than 350Klps.

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