101 lines
2.2 KiB
ArmAsm
101 lines
2.2 KiB
ArmAsm
|
//++
|
||
|
|
//
|
||
|
|
// Module Name:
|
||
|
|
//
|
||
|
|
// gettick.s
|
||
|
|
//
|
||
|
|
// Abstract:
|
||
|
|
//
|
||
|
|
// This module implements the system service that returns the number
|
||
|
|
// of milliseconds since the system was booted.
|
||
|
|
//
|
||
|
|
// Author:
|
||
|
|
//
|
||
|
|
// William K. Cheung (wcheung) 25-Sep-95
|
||
|
|
//
|
||
|
|
// Revision History:
|
||
|
|
//
|
||
|
|
// 02-Feb-96 Updated to EAS2.1
|
||
|
|
//
|
||
|
|
//--
|
||
|
|
|
||
|
|
#include "ksia64.h"
|
||
|
|
|
||
|
|
.file "gettick.s"
|
||
|
|
|
||
|
|
.global KeTickCount
|
||
|
|
.global ExpTickCountMultiplier
|
||
|
|
|
||
|
|
//++
|
||
|
|
//
|
||
|
|
// ULONG
|
||
|
|
// NtGetTickCount (
|
||
|
|
// VOID
|
||
|
|
// )
|
||
|
|
//
|
||
|
|
// Routine Description:
|
||
|
|
//
|
||
|
|
// This function computes the number of milliseconds since the system
|
||
|
|
// was booted. The computation is performed by multiplying the clock
|
||
|
|
// interrupt count by a scaled fixed binary multiplier and then right
|
||
|
|
// shifting the 64-bit result to extract the 32-bit millisecond count.
|
||
|
|
//
|
||
|
|
// The multiplier fraction is scaled by 24 bits. Thus for a 100 Hz clock
|
||
|
|
// rate, there are 10 ticks per millisecond, and the multiplier is
|
||
|
|
// 0x0a000000 (10 << 24). For a 128 Hz clock rate, there are 7.8125, or
|
||
|
|
// 7 13/16 ticks per millisecond, and so the multiplier is 0x07d00000.
|
||
|
|
//
|
||
|
|
// This effectively replaces a (slow) divide instruction with a (fast)
|
||
|
|
// multiply instruction. The multiplier value is only calculated once
|
||
|
|
// based on the TimeIncrement value (clock tick interval in 100ns units).
|
||
|
|
//
|
||
|
|
// N.B. The tick count value wraps every 2^32 milliseconds (49.71 days).
|
||
|
|
//
|
||
|
|
// Arguments:
|
||
|
|
//
|
||
|
|
// None.
|
||
|
|
//
|
||
|
|
// Return Value:
|
||
|
|
//
|
||
|
|
// The number of milliseconds since the system was booted is returned
|
||
|
|
// as the function value.
|
||
|
|
//
|
||
|
|
//--
|
||
|
|
|
||
|
|
LEAF_ENTRY(NtGetTickCount)
|
||
|
|
|
||
|
|
//
|
||
|
|
// load zero-extended operands
|
||
|
|
//
|
||
|
|
|
||
|
|
add t0 = @gprel(KeTickCount), gp
|
||
|
|
add t1 = @gprel(ExpTickCountMultiplier), gp
|
||
|
|
;;
|
||
|
|
|
||
|
|
ld4 t2 = [t0]
|
||
|
|
ld4 t3 = [t1]
|
||
|
|
;;
|
||
|
|
|
||
|
|
//
|
||
|
|
// compute 64-bit product
|
||
|
|
//
|
||
|
|
|
||
|
|
setf.sig fs2 = t2
|
||
|
|
setf.sig fs3 = t3
|
||
|
|
;;
|
||
|
|
xmpy.lu fs1 = fs2, fs3
|
||
|
|
;;
|
||
|
|
|
||
|
|
//
|
||
|
|
// shift off 24-bit fraction part and
|
||
|
|
// the 32-bit canonical ULONG integer part.
|
||
|
|
//
|
||
|
|
|
||
|
|
getf.sig v0 = fs1
|
||
|
|
;;
|
||
|
|
extr.u v0 = v0, 24, 32
|
||
|
|
|
||
|
|
br.ret.sptk.clr brp // return
|
||
|
|
|
||
|
|
LEAF_EXIT(NtGetTickCount)
|