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Re: Compilation performance comparison of 3.5.0 and TreeSSA treeson MICO sources as requested in: [tree-ssa] Merge status 2004-05-03

On Wed, 5 May 2004, Daniel Berlin wrote:

> Note that in almost all of his cases, the parser takes at least 15%,
> and usually 30%+ of the time of compilation.

Yes, that's true. Parser and name lookup are most expensive tasks. But how
is it possible that trunk is so much (~20%) faster than tree-ssa, when
tree-ssa is based on trunk?

> Note that the parser times are significantly slower with tree-ssa than
> they are for mainline (be it because of memory locality, bad time
> accounting, or whatever)

Yes, but why?

> I only mention this because i'm pretty sure that right now, even if we
> made gimplification take no time on these testcases, we'd still have a
> large percent regression just from the parser times.

Agree, but maybe it just tell something about not so good optimizations on
tree-ssa branch in comparison with trunk, i.e. trunk optimizes C++ parser
much better... Is it possible to not bootstrap tree-ssa, but just compile
it by GCC3.4.0/3.5.0 and see if parser is faster? If so, how?


Karel Gardas        
ObjectSecurity Ltd. 

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