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Re: The speed of the compiler, was: Re: Combine four insns

Diego Novillo wrote:

On 10-08-09 10:54 , Toon Moene wrote:

Most of these "compiles" are -O0 -g compiles, for obvious reasons (why
spend time on optimization when you don't even know the code is correct ?)

Internally, we have been working on build time improvements for a few months. We are not looking at just the compiler, but the entire toolchain.

As I've posted in other threads, our main consumer of compilation time is the C++ front end. Hands down. It consistently takes between 70% and 80% of compilation time across the board. Furthermore, this is independent from the optimization level. The optimizers never take more than 10-15% of total compilation time, on average.

As I pointed out in my 2007 GCC Summit talk, the Fortran Front End *already* (i.e., before anyone approved it) performs optimization on the Front End internal representation of a Fortran program / subroutine.

Is this also true for C++ ? In that case it might be useful to curb Front End optimizations when -O0 is given ...

Or is there a reason why the C++ Front End has to do so much work (even when not bothering with language specific optimizations) ?

Toon Moene - e-mail: - phone: +31 346 214290
Saturnushof 14, 3738 XG  Maartensdijk, The Netherlands
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