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From: Bengt Larsson <lists DOT cygwin4 AT bengtl DOT net>
To: cygwin AT cygwin DOT com
Subject: Re: Performance problem with gcc 4.9.2-3 on 64 bit
Date: Sat, 28 Feb 2015 18:56:39 +0100
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References: <cm61fadkltbqshdmtiil4nb50b0gf1n3qg AT 4ax DOT com> <54F13EA8 DOT 9060609 AT gmail DOT com>
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Marco Atzeri wrote:
>On 2/27/2015 5:49 PM, Bengt Larsson wrote:
>> Below are two benchmarks that explore maximum floating point
>> performance. loopm6 is double precision floating point and loopm6fp is
>> parallell single-precision. They are manually unrolled multiply-add
>> loops.
>>
>> I used to reach 2.8 and 11 GFlops on these. Now I only get
>> 2 and 6.
>>
>> If you explore the inner loop with gcc -O2 -S you can see that it seems
>> to use few registers.
>>
>> If you run them, there is a parameter expected. I use 30000 - 50000.
>>
>> gcc 4.9.2-3 on 64-bit. I use gcc -O2.
>>
>
>May be
>https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53967

I think that was longer ago. On the version before 4.9.* on Cygwin I got
full speed. 

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