Performance problem with gcc 4.9.2-3 on 64 bit

[Bengt Larsson <lists dot cygwin4 at bengtl dot net>]

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.

Attachment: loopm6.c
Description: Binary data

Attachment: loopm6fp.c
Description: Binary data

Attachment: timers.h
Description: Binary data

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