Changes to make simple cpu handle pcs appropriately for x86

--HG--
extra : convert_revision : cf68886d53301e0a63705247bd7d66b2ff08ea84
This commit is contained in:
Gabe Black 2007-05-18 10:42:50 -07:00
parent c382bdf93d
commit 6a6e62014e
3 changed files with 32 additions and 10 deletions

View file

@ -557,7 +557,7 @@ AtomicSimpleCPU::tick()
} }
} }
if(predecoder.needMoreBytes() || fault != NoFault) if(fault != NoFault || !stayAtPC)
advancePC(fault); advancePC(fault);
} }

View file

@ -91,6 +91,9 @@ BaseSimpleCPU::BaseSimpleCPU(Params *p)
lastDcacheStall = 0; lastDcacheStall = 0;
threadContexts.push_back(tc); threadContexts.push_back(tc);
fetchOffset = 0;
stayAtPC = false;
} }
BaseSimpleCPU::~BaseSimpleCPU() BaseSimpleCPU::~BaseSimpleCPU()
@ -335,12 +338,9 @@ BaseSimpleCPU::setupFetchRequest(Request *req)
thread->readNextPC()); thread->readNextPC());
#endif #endif
// This will generate a mask which aligns the pc on MachInst size
// boundaries. It won't work for non-power-of-two sized MachInsts, but
// it will work better than a hard coded mask.
const Addr PCMask = ~(sizeof(MachInst) - 1); const Addr PCMask = ~(sizeof(MachInst) - 1);
req->setVirt(0, thread->readPC() & PCMask, sizeof(MachInst), 0, Addr fetchPC = thread->readPC() + fetchOffset;
thread->readPC()); req->setVirt(0, fetchPC & PCMask, sizeof(MachInst), 0, thread->readPC());
Fault fault = thread->translateInstReq(req); Fault fault = thread->translateInstReq(req);
@ -368,21 +368,35 @@ BaseSimpleCPU::preExecute()
// decode the instruction // decode the instruction
inst = gtoh(inst); inst = gtoh(inst);
//If we're not in the middle of a macro instruction //If we're not in the middle of a macro instruction
if (!curMacroStaticInst) { if (!curMacroStaticInst) {
StaticInstPtr instPtr = NULL; StaticInstPtr instPtr = NULL;
//Predecode, ie bundle up an ExtMachInst //Predecode, ie bundle up an ExtMachInst
//This should go away once the constructor can be set up properly //This should go away once the constructor can be set up properly
predecoder.setTC(thread->getTC()); predecoder.setTC(thread->getTC());
//If more fetch data is needed, pass it in. //If more fetch data is needed, pass it in.
const Addr PCMask = ~(sizeof(MachInst) - 1);
if(predecoder.needMoreBytes()) if(predecoder.needMoreBytes())
predecoder.moreBytes(thread->readPC(), 0, inst); predecoder.moreBytes((thread->readPC() & PCMask) + fetchOffset,
0, inst);
else else
predecoder.process(); predecoder.process();
//If an instruction is ready, decode it
if (predecoder.extMachInstReady()) //If an instruction is ready, decode it. Otherwise, we'll have to
//fetch beyond the MachInst at the current pc.
if (predecoder.extMachInstReady()) {
#if THE_ISA == X86_ISA
thread->setNextPC(thread->readPC() + predecoder.getInstSize());
#endif // X86_ISA
stayAtPC = false;
instPtr = StaticInst::decode(predecoder.getExtMachInst()); instPtr = StaticInst::decode(predecoder.getExtMachInst());
} else {
stayAtPC = true;
fetchOffset += sizeof(MachInst);
}
//If we decoded an instruction and it's microcoded, start pulling //If we decoded an instruction and it's microcoded, start pulling
//out micro ops //out micro ops
@ -450,12 +464,14 @@ BaseSimpleCPU::postExecute()
void void
BaseSimpleCPU::advancePC(Fault fault) BaseSimpleCPU::advancePC(Fault fault)
{ {
//Since we're moving to a new pc, zero out the offset
fetchOffset = 0;
if (fault != NoFault) { if (fault != NoFault) {
curMacroStaticInst = StaticInst::nullStaticInstPtr; curMacroStaticInst = StaticInst::nullStaticInstPtr;
fault->invoke(tc); fault->invoke(tc);
thread->setMicroPC(0); thread->setMicroPC(0);
thread->setNextMicroPC(1); thread->setNextMicroPC(1);
} else if (predecoder.needMoreBytes()) { } else {
//If we're at the last micro op for this instruction //If we're at the last micro op for this instruction
if (curStaticInst && curStaticInst->isLastMicroOp()) { if (curStaticInst && curStaticInst->isLastMicroOp()) {
//We should be working with a macro op //We should be working with a macro op

View file

@ -137,6 +137,12 @@ class BaseSimpleCPU : public BaseCPU
StaticInstPtr curStaticInst; StaticInstPtr curStaticInst;
StaticInstPtr curMacroStaticInst; StaticInstPtr curMacroStaticInst;
//This is the offset from the current pc that fetch should be performed at
Addr fetchOffset;
//This flag says to stay at the current pc. This is useful for
//instructions which go beyond MachInst boundaries.
bool stayAtPC;
void checkForInterrupts(); void checkForInterrupts();
Fault setupFetchRequest(Request *req); Fault setupFetchRequest(Request *req);
void preExecute(); void preExecute();