I have looked over the history of changes for this part of code, and I must say it was carefully crafted to satisfy a whole lot of different versions of Intel Compiler and GCC, on Linux and Mac OS X. That includes the "esp" in clobbered list which was not there originally but added later for a reason. So knowing the exact version of the compileris very important to reproduce the behavior, and understand what could/shouldbe changed, and in what way.