Re: Performance degradation on g++ 4.6

[Oleg Smolsky <oleg dot smolsky at riverbed dot com>]

On 2011/7/29 14:07, Xinliang David Li wrote:
> Profiling tools are your best friend here. If you don't have access to
> any, the least you can do is to build the program with -pg option and
> use gprof tool to find out differences.
The test suite has a bunch of very basic C++ tests that are executed an 
enormous number of times. I've built one with the obvious performance 
degradation and attached the source, output and reports.

Here are some highlights:
    v4.1:    Total absolute time for int8_t constant folding: 30.42 sec
    v4.6:    Total absolute time for int8_t constant folding: 43.32 sec

Every one of the tests in this section had degraded... the first half 
more than the second. I am not sure how much further I can take this - 
the benchmarked code is very short and plain. I can post disassembly for 
one (some?) of them if anyone is willing to take a look...

Thanks,
Oleg.

Attachment: gmon41.prof
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Attachment: report41
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Attachment: simple_types_constant_folding.cpp
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Attachment: report46
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Attachment: gmon46.prof
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Attachment: benchmark_shared_tests.h
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