RE: Precompiled headers (or other speed ups)

[David Korn <dkorn at pixelpower dot com>]

><<  Well, only really surprising if you assume the parsing code is well
>written :-) After all, the mid/backend is mostly doing memory-memory
>transforms on the trees, and that's going to run as fast as your cache
>and cpu can handle.  Parsers, OTOH, have to I/O.  Badly written parsers
>might even use c stdio functions to fgetc the entire file one char at a
>time....
>>>
>
>Sure, but that presumably is an easy thing to fix. In GNAT, the entire
>file is read with a single read, and then all access to the file is to
>the in memory copy, which stays around throughout the compilation.

  Oh yeah; I was just suggesting it wouldn't be *surprising*, not that it
would be 'right'!  Last time I looked at bison (or was it lex or yacc? I
forget) was around '95 and it did tend to turn out fairly sucky code (in
terms of f-stdio) if you didn't know what you were doing and how to hook
it into a memory buffer.  I haven't looked at the gcc parsers yet but I
would hope that they don't have such obvious design flaws.....

  Another thing that could eat time in a parser would be if there were
numerous shift-reduce conflicts that caused a lot of backtracking on fairly
common constructs.  That's just a for-example also :)

    DaveK

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