Performance regression of generated numerical code

[Martin Reinecke <martin at MPA-Garching dot MPG dot DE>]

Hi,

I have noticed a big performance decrease in one of my numerical codes
when switching from gcc 4.4 to gcc 4.5. A small test case is attached.
When compiling this test case with "gcc -O3 perf.c -lm -std=c99"
and executing the resulting binary, the CPU time with the head of
the 4.4 branch is about 1.1s, with the head of the trunk it is 2.1s.

This is on a Pentium D CPU. I have verified that both binaries produce
identical results.

If I can do anything to help locate the reason for this slowdown, I'd be
glad to help, but I must admit that I'm no good at interpreting assembler.

Any insight would be greatly appreciated.

Thanks,
  Martin

Attachment: perf.c
Description: Text document