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Re: gcc compile-time performance
- From: dewar at gnat dot com (Robert Dewar)
- To: dewar at gnat dot com, neil at daikokuya dot demon dot co dot uk
- Cc: gcc at gcc dot gnu dot org, robertlipe at usa dot net
- Date: Sat, 18 May 2002 08:19:39 -0400 (EDT)
- Subject: Re: gcc compile-time performance
> I think a big killer for GCC is the combination of overly-complex bison
> parsers (necessary to keep state for various wacky things we want to do;
> it's much easier to keep state for these things with a recursive descent
> parser) and the genericity of "tree". I strongly believe this is a
> performance issue in the C family of front ends; for example in the
> C front end there are many contortions in place for no other reason
> than we use bison.
Well for sure there is no reason to spend any measurable amount of time
in parsing (or lexical analysis for that matter), but I have certainly
seen compilers that manage amazingly to spend significant amounts of
time in these functions, typically from the use of inefficient tools.
Is this really a time eater? Often I see in the g++ world the phrase
"parsing" to encompass what in normal terminology is both parsing and
static semantic analysis, and most certainly the static semantic analysis
in C is non-trivial and potentially time consuming.