Hi Jochen,
here are my results.
Intel(R) Core(TM) i7-3770 CPU @ 3.40GHz (SSE4)
++++++++++++++++++2 of 20 tests valid, loop overhead is approx. 191/100 cycles
5012 cycles for 100 * log Asm
16923 cycles for 100 * log Asm with checks
21842 cycles for 100 * log CRT
22318 cycles for 100 * logC Math.h
11258 cycles for 100 * log Asm
18792 cycles for 100 * log Asm with checks
15586 cycles for 100 * log CRT
19173 cycles for 100 * logC Math.h
10486 cycles for 100 * log Asm
16812 cycles for 100 * log Asm with checks
21828 cycles for 100 * log CRT
22309 cycles for 100 * logC Math.h
13 bytes for log Asm
19 bytes for log Asm with checks
24 bytes for log CRT
23 bytes for logC Math.h
R8=-5.54677872584653642 for t log Asm
R8=-5.54677872584653642 for t log Asm with checks
R8=-5.54677872584653642 for t log CRT
R8=-5.54677872584653642 for t logC Math.h
--- ok ---
I can't re-build the EXE, because I haven't crt.lib. But transzendental functions are mostly awkward implemented by compiler builders and time consuming, too.
Gunther