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More realistic "mftb" implementation, aka. fix AbsoluteToNanoseconds() and

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generally speaking UpTime()-based stopwatchers.
This commit is contained in:
gbeauche 2004-06-22 15:48:50 +00:00
parent 070ac7079f
commit 1988a45a16
1 changed files with 42 additions and 2 deletions
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44
SheepShaver/src/kpx_cpu/src/cpu/ppc/ppc-execute.cpp
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@ -35,6 +35,10 @@
#include "basic-kernel.hpp"
#endif
#ifdef SHEEPSHAVER
#include "main.h"
#endif
#if ENABLE_MON
#include "mon.h"
#include "mon_disass.h"
@ -1114,14 +1118,50 @@ void powerpc_cpu::execute_mtspr(uint32 opcode)
increment_pc(4);
}
// Compute with 96 bit intermediate result: (a * b) / c
static uint64 muldiv64(uint64 a, uint32 b, uint32 c)
{
union {
uint64 ll;
struct {
#ifdef WORDS_BIGENDIAN
uint32 high, low;
#else
uint32 low, high;
#endif
} l;
} u, res;
u.ll = a;
uint64 rl = (uint64)u.l.low * (uint64)b;
uint64 rh = (uint64)u.l.high * (uint64)b;
rh += (rl >> 32);
res.l.high = rh / c;
res.l.low = (((rh % c) << 32) + (rl & 0xffffffff)) / c;
return res.ll;
}
static inline uint64 get_tb_ticks(void)
{
uint64 ticks;
#ifdef SHEEPSHAVER
const uint32 TBFreq = BusClockSpeed / 4;
ticks = muldiv64(GetTicks_usec(), TBFreq, 1000000);
#else
const uint32 TBFreq = 25 * 1000 * 1000; // 25 MHz
ticks = muldiv64((uint64)clock(), TBFreq, CLOCKS_PER_SEC);
#endif
return ticks;
}
template< class TBR >
void powerpc_cpu::execute_mftbr(uint32 opcode)
{
uint32 tbr = TBR::get(this, opcode);
uint32 d;
switch (tbr) {
case 268: d = clock(); break;
case 269: d = 0; break;
case 268: d = (uint32)get_tb_ticks(); break;
case 269: d = (get_tb_ticks() >> 32); break;
default: execute_illegal(opcode);
}
operand_RD::set(this, opcode, d);