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Re: [patch] passes.c: Run CSE only once after GCSE instead oftwice or more.


Hi Giovanni,

> Is it possible to test such performance patches also with
> preprocessed C++ files? It is undoubtful that C++ excerices the
> optimizers much more than C, so I think it makes sense to make sure
> that disabling these optimizations doesn't make use lose in
> performance there.

I took MICO as compile time benchmark.

Here is a timing in seconds for five runs of ./cc1plus -quiet -O2
-fno-random-seed -o /dev/null.

          original patched   diff%
----------------------------------
except2.ii  15.395  15.212 -1.188%
iop.ii      31.844  31.310 -1.676%
pi_impl.ii  33.453  33.007 -1.333%
static.ii   31.122  30.781 -1.095%
mico-ii    371.200 368.957 -0.604%

mico-ii files were compiled only once.

There was no difference in the generated code with or without my patch
except 3 out of 87 preprocessed C++ source files.  One of them had
minor register allocation differences.  The other two had some real
differences.  I haven't what kind of differences they are.

I haven't done any run-time performance measurement.  Any suggestion
for C++?

Kazu Hirata


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