Performance loss in migration from VS6 to VS2005

[darietti7]

I am having a performance loss of about 15% when migrating an application to VS2005.

Both builds use icl 9.0, same code, same makefiles, optimizations, etc...

The only difference is: STL, MSVCRx.dllandMSVCPx.dll

The result is a size increase (dlls & exes size is 10%-100% larger) and a performance loss.

Any ideas? Anyone with the same problem?

Thanks in advance

PS: OS is W2K, CPU is Xeon nocona, optimization flags are /O3 /QaxWNP /Qipo

[TimP]

Are you really gaining performance on 4 different architectures which matter to you by asking for up to 4 different code paths? Check -QxW, N, P separately, and discard any which don't give improved performance over the preceding one. If you don't need backward compatibility beyond P-III, maybe a smaller range, like -QxKW, will do the job. K and W might not produce different code paths so often. If code size, or short loops, are more important to performance than long loops requiring interchange optimizations, -O1 might do better, and full ipo may not be the best.
For large applications, it's often necessary to choose options appropriate to various parts of the build, to get best performance. That may involve profiling the builds with various candidate options, to find out which options are best, function by function.

[darietti7]

Thanks for the info about optimization flags. We are still in the process of reaching the best build options.

Aside from that, what worries me is the performance loss with same code + same options + same compiler

The problemmust have something to do with what is different between VS6 & VS2005 (apart fromMS compiler wich we are not using): STL (and how ICL compiles the templated code), MSVCRT, MSVCP, etc...

Is it possible I am the only one getting worse performance when migrating to VS2005...