blob: 42a0e23203280ed0bf438bb4ec6593128818adad (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
|
%include "defs.asm"
; RDTSC64.ASM
;
; Author: Agner Fog
; Date created: 2003
; Last modified: 2008-10-16
; Description:
;
; Copyright (c) 2009 GNU General Public License www.gnu.org/licenses
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
default rel
global ReadTSC: function
SECTION .text align=16
; ********** ReadTSC function **********
; C++ prototype:
; extern "C" __int64 ReadTSC (void);
; This function returns the value of the time stamp counter, which counts
; clock cycles. To count how many clock cycles a piece of code takes, call
; Rdtsc before and after the code to measure and calculate the difference.
; The number of clock cycles taken by the ReadTSC function itself is approximately:
; Core 2: 730
; Pentium 4: 700
; Pentium II and Pentium III: 225
; AMD Athlon 64, Opteron: 126
; Does not work on 80386 and 80486.
; Note that clock counts may not be fully reproducible on Intel Core and
; Core 2 processors because the clock frequency can change. More reliable
; instruction timings are obtained with the performance monitor counter
; for "core clock cycles". This requires a kernel mode driver as the one
; included with www.agner.org/optimize/testp.zip.
ReadTSC:
push rbx ; ebx is modified by cpuid
sub eax, eax ; 0
cpuid ; serialize
rdtsc ; read time stamp counter into edx:eax
shl rdx, 32
or rax, rdx ; combine into 64 bit register
push rax
sub eax, eax
cpuid ; serialize
pop rax ; return value
pop rbx
ret
;ReadTSC ENDP
|
