Re: Incremental gcc

[Mike Stump <mrs at apple dot com>]

On Mar 25, 2006, at 9:14 PM, Camm Maguire wrote:
> Greetings! GCL is a lisp compiler system which outputs C code normally
> compiled by gcc into an object, which is then loaded and relocated
> into the running GCL image.  In lisp, compiling is a very incremental
> process, with many, often thousands of small functions compiled one at
> a time.  GCL/gcc compilation speed would be greatly improved if gcc
> could be run in some sort of incremental mode

Ignoring an ideal world for a second, if you have large amounts of  
headers that are stable that are needed for compilation, be sure to  
precompile them.  After that, batch up all code to be compiled into  
larger unit and compile it all in one go, as it saves a substantial  
amount of time (2x faster maybe), this way startup costs are amortized.

Longer term, it would be nice to have someone from your camp layout  
where the time is spent and what changes might be worth while in gcc  
to make it more suitable for that type of work.

You can run the compiler via stdin and stdout:

$ gcc -x c - -o - -S
int i;
main() { }
^D      .section __TEXT,__text,regular,pure_instructions
        .section  
__TEXT,__picsymbolstub1,symbol_stubs,pure_instructions,32
        .machine ppc
        .text
        .align 2
        .globl _main
_main:
        stmw r30,-8(r1)
        stwu r1,-48(r1)
        mr r30,r1
        lwz r1,0(r1)
        lmw r30,-8(r1)
        blr
.comm _i,4
        .subsections_via_symbols

if you want, so that isn't very hard to do.  The sub-problem of an as  
that can operate this way is off-topic for this list, so I won't  
address it.

Long term, might be nice to have a way to wire in the assemblers into  
gcc directly.  If you guys feel ambitious, that might be doable; but  
since gc is driven by people that want to code, you'll have to find  
someone that wants to code it up.  The java folks might be interested  
in JITifying the compiler as well, if enough people are interested in  
doing that, it might be an interesting direction to take gcc, though  
building in as strikes me as a prerequisite.