/*?
?*?clock.c?-?Routines?for?using?the?cycle?counters?on?x86?
?*???????????Alpha?and?Sparc?boxes.
?*?
?*?Copyright?（c）?2002?R.?Bryant?and?D.?O‘Hallaron?All?rights?reserved.
?*?May?not?be?used?modified?or?copied?without?permission.
?*/

#include?
#include?
#include?
#include?
#include?“clock.h“


/*******************************************************?
?*?Machine?dependent?functions?
?*
?*?Note:?the?constants?__i386__?and??__alpha
?*?are?set?by?GCC?when?it?calls?the?C?preprocessor
?*?You?can?verify?this?for?yourself?using?gcc?-v.
?*******************************************************/

#if?defined（__i386__）??
/*******************************************************
?*?Pentium?versions?of?start_counter（）?and?get_counter（）
?*******************************************************/


/*?$begin?x86cyclecounter?*/
/*?Initialize?the?cycle?counter?*/
static?unsigned?cyc_hi?=?0;
static?unsigned?cyc_lo?=?0;


/*?Set?*hi?and?*lo?to?the?high?and?low?order?bits??of?the?cycle?counter.??
???Implementation?requires?assembly?code?to?use?the?rdtsc?instruction.?*/
void?access_counter（unsigned?*hi?unsigned?*lo）
{
????asm（“rdtsc;?movl?%%edx%0;?movl?%%eax%1“???/*?Read?cycle?counter?*/
	:?“=r“?（*hi）?“=r“?（*lo）????????????????/*?and?move?results?to?*/
	:?/*?No?input?*/????????????????????????/*?the?two?outputs?*/
	:?“%edx“?“%eax“）;
}

/*?Record?the?current?value?of?the?cycle?counter.?*/
void?start_counter（）
{
????access_counter（&cyc_hi?&cyc_lo）;
}

/*?Return?the?number?of?cycles?since?the?last?call?to?start_counter.?*/
double?get_counter（）
{
????unsigned?ncyc_hi?ncyc_lo;
????unsigned?hi?lo?borrow;
????double?result;

????/*?Get?cycle?counter?*/
????access_counter（&ncyc_hi?&ncyc_lo）;

????/*?Do?double?precision?subtraction?*/
????lo?=?ncyc_lo?-?cyc_lo;
????borrow?=?lo?>?ncyc_lo;
????hi?=?ncyc_hi?-?cyc_hi?-?borrow;
????result?=?（double）?hi?*?（1?<????if?（result?	fprintf（stderr?“Error:?counter?returns?neg?value:?%.0f\n“?result）;
????}
????return?result;
}
/*?$end?x86cyclecounter?*/

#elif?defined（__alpha）

/****************************************************
?*?Alpha?versions?of?start_counter（）?and?get_counter（）
?***************************************************/

/*?Initialize?the?cycle?counter?*/
static?unsigned?cyc_hi?=?0;
static?unsigned?cyc_lo?=?0;


/*?Use?Alpha?cycle?timer?to?compute?cycles.??Then?use
???measured?clock?speed?to?compute?seconds?
*/

/*
?*?counterRoutine?is?an?array?of?Alpha?instructions?to?access?
?*?the?Alpha‘s?processor?cycle?counter.?It?uses?the?rpcc?
?*?instruction?to?access?the?counter.?This?64?bit?register?is?
?*?divided?into?two?parts.?The?lower?32?bits?are?the?cycles?
?*?used?by?the?current?process.?The?upper?32?bits?are?wall?
?*?clock?cycles.?These?instructions?read?the?counter?and?
?*?convert?the?lower?32?bits?into?an?unsigned?int?-?this?is?the?
?*?user?space?counter?value.
?*?NOTE:?The?counter?has?a?very?limited?time?span.?With?a?
?*?450MhZ?clock?the?c