I was following-up on a behavioral difference between a program whencompiled with GCC C++ and Intel C++ and thought I would pass the information on to the forum in the event that this is important to its readers.
Intel C++ generates code containing the P4 "PAUSE" instruction, whereas GCC C++ generates code containing "rep; nop". This is due to code generation assuming 80386 compatability although in my test case I was generating a 64-bit application. PAUSE came in with P4.
The issue is that the PAUSE is a low-power consumingshort duration stall, whereas "rep;nop" will be a short duration compute intensive stall. The duration islikely much shorter than PAUSE, and the power consumption will be higher. This issue is observed in code like the following on a multi-threaded program:
volatile int flag = 0;