http://llvm.org/bugs/show_bug.cgi?id=12750
Benjamin Kramer <[email protected]> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |RESOLVED Resolution| |FIXED --- Comment #9 from Benjamin Kramer <[email protected]> 2012-12-11 14:50:08 CST --- (In reply to comment #8) > xorl should not have a performance impact (except for size) because this idiom > is detected by the CPU frontend. Read on. This was a curious microarchitectural issue with corei7 (and I think core2, too). If an inner loop has more than a specific number of µops performance drops considerably. xorl %eax, %eax is about as cheap as instructions can get on x86 but it still consumes 1 µop and can slow down an inner loop if this µop pushes the count over the limit. That aside, this bug was fixed a while ago and can be closed. -- Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email ------- You are receiving this mail because: ------- You are on the CC list for the bug. _______________________________________________ LLVMbugs mailing list [email protected] http://lists.cs.uiuc.edu/mailman/listinfo/llvmbugs
