gcc-4.5.0: Major Slowdown in Freecell Solver after an innocent patch on a Linux P4-2.4GHz

[Andrew Haley]

On 06/23/2010 11:10 AM, Shlomi Fish wrote:
> Hi all,
> 
> I've been using gcc-4.5.0 with -flto to build Freecell Solver ( 
> http://fc-solve.berlios.de/ ) - a C library for solving several types of 
> Solitaire games. During one commit to the svn repository, I got a major 
> slowdown in the performance of a benchmark. The attached text file explains 
> how to reproduce this.
> 
> Here's what I know:
> 
> 1. There doesn't appear to be a slowdown on my Acer x86-64 Dual Core laptop.
> 
> 2. It's only on my Pentium 4 2.4 GHz machine.
> 
> 3. gcc-4.4.3-2mnb2 is better in this respect, though naturally, without 
> gcc-4.5.0's -flto it produces slower binaries.
> 
> 4. I'm running Mandriva GNU/Linux Cooker in case that matters.
> 
> 5. I'm using Google's tcmalloc - 
> http://goog-perftools.sourceforge.net/doc/tcmalloc.html .
> 
> Can anyone shed some light on why this is the case?

Do you have profile data?  If not, I'd start with oprofile.

Andrew.