strlen

Variants

Name	Description
stock	MI C version
SSE2	pcmpeqb and pmovmskb
SSE4.2	pcmpestri and pcpmestrm
AVX	128-bit vpcmpeqb and vpmovmskb
ERMS	repne scasb for machines with ERMS

Note: clang was too smart and optimized plain strlen calls away, so I had to create a copy of the C version called strlen_mi() to fool it.

Machines Tested

CPU	Speed (GHz)	Notes
Xeon X5365	3.00	2 x 4 Supermicro X7DBU
Xeon X5482	3.20	2 x 4 Supermicro X7DWN+
Xeon X5675	3.07	Westmere 2 x 6 Supermicro X8DTU
Core i5-2520M	2.50	Sandy Bridge 1 x 4 Thinkpad X220 (4286)
Xeon E5-2680	2.70	Romley 2 x 8 Supermicro X9DRW
Xeon E5-2667 v2	3.30	Romley V2 2 x 8 Supermicro X9DRW

Test Cases

Name	Description
page	aligned string one page - 1 long
short	aligned string 14 characters long
short2	aligned string 32 characters long
short3	aligned string 48 characters long
offset	4 byte offset string 126 characters long
offset2	7 byte offset string 95 characters long

Results

The numbers are the min value in the distribution where the values are a TSC delta across a single invocation of the test.

CPU	Test / Variant
	page					short					short2					short3					offset					offset2
	stock	SSE2	SSSE4.2	AVX	ERMS	stock	SSE2	SSSE4.2	AVX	ERMS	stock	SSE2	SSSE4.2	AVX	ERMS	stock	SSE2	SSSE4.2	AVX	ERMS	stock	SSE2	SSSE4.2	AVX	ERMS	stock	SSE2	SSSE4.2	AVX	ERMS
Xeon X5365	1386	864	--	--	16506	81	72	--	--	180	90	72	--	--	252	90	81	--	--	315	144	108	--	--	630	135	108	--	--	504
Xeon X5482	1608	808	--	--	16464	48	40	--	--	136	48	40	--	--	140	56	40	--	--	264	80	80	--	--	592	72	72	--	--	464
Xeon X5675	1592	848	2100	--	8252	60	24	24	--	92	32	46	32	--	124	78	46	83	--	156	76	64	104	--	316	64	56	88	--	256