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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.

/*XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XX                                                                           XX
XX                 State machine used in the JIT                             XX
XX                                                                           XX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX
*/

#include "jitpch.h"
#ifdef _MSC_VER
#pragma hdrstop
#endif

#include "smcommon.cpp"

//
// The array to map from EE opcodes (i.e. CEE_ ) to state machine opcodes (i.e. SM_ )
//
const SM_OPCODE smOpcodeMap[] =
{
    #define OPCODEMAP(eename,eestring,smname) smname,
    #include "smopcodemap.def"
    #undef  OPCODEMAP
};


// ????????? How to make this method inlinable, since it refers to smOpcodeMap????
/* static */ SM_OPCODE    CodeSeqSM::MapToSMOpcode(OPCODE opcode)
{
    assert(opcode < CEE_COUNT);

    SM_OPCODE smOpcode = smOpcodeMap[opcode];
    assert(smOpcode < SM_COUNT);
    return smOpcode;
}

void CodeSeqSM::Start(Compiler * comp) 
{    
    pComp             = comp;
    States            = gp_SMStates;
    JumpTableCells    = gp_SMJumpTableCells;
    StateWeights      = gp_StateWeights;
    NativeSize        = 0;

    Reset();  
}

void CodeSeqSM::Reset() 
{
    curState      = SM_STATE_ID_START;

#ifdef DEBUG
    // Reset the state occurence counts
    memset(StateMatchedCounts, 0, sizeof(StateMatchedCounts));
#endif

}

void CodeSeqSM::End() 
{
    if (States[curState].term)
    {
        TermStateMatch(curState DEBUGARG(pComp->verbose));
    }
}

void  CodeSeqSM::Run(SM_OPCODE opcode DEBUGARG(int level))
{    
    SM_STATE_ID nextState;
    SM_STATE_ID rollbackState;

    SM_OPCODE   opcodesToRevisit[MAX_CODE_SEQUENCE_LENGTH];

    assert(level<=MAX_CODE_SEQUENCE_LENGTH);

_Next:
    nextState = GetDestState(curState, opcode);    

    if (nextState != 0)
    {
        // This is easy, Just go to the next state.
        curState = nextState;
        return;            
    }

    assert(curState != SM_STATE_ID_START); 
        
    if (States[curState].term)
    {
        TermStateMatch(curState DEBUGARG(pComp->verbose));
        curState = SM_STATE_ID_START;
        goto _Next;
    }
        
    // This is hard. We need to rollback to the longest matched term state and restart from there.

    rollbackState = States[curState].longestTermState;
    TermStateMatch(rollbackState DEBUGARG(pComp->verbose));

    assert(States[curState].length > States[rollbackState].length);
     
    unsigned numOfOpcodesToRevisit = States[curState].length - States[rollbackState].length + 1;
    assert(numOfOpcodesToRevisit > 1   &&
           numOfOpcodesToRevisit <= MAX_CODE_SEQUENCE_LENGTH); // So it can fit in the local array opcodesToRevisit[]

    SM_OPCODE * p = opcodesToRevisit + (numOfOpcodesToRevisit - 1);

    *p = opcode;

    // Fill in the local array:
    for (unsigned i = 0; i<numOfOpcodesToRevisit-1; ++i) 
    {
        * (--p) = States[curState].opc;
        curState = States[curState].prevState;
    }

    assert(curState == rollbackState);    

    // Now revisit these opcodes, starting from SM_STATE_ID_START.
    curState = SM_STATE_ID_START;
    for (p = opcodesToRevisit; p< opcodesToRevisit + numOfOpcodesToRevisit; ++p)
    {
        Run(*p DEBUGARG(level+1));
    }    
}


SM_STATE_ID  CodeSeqSM::GetDestState(SM_STATE_ID srcState, SM_OPCODE opcode)
{
    assert(opcode < SM_COUNT);
         
    JumpTableCell * pThisJumpTable = (JumpTableCell * )(((PBYTE)JumpTableCells) + States[srcState].jumpTableByteOffset);

    JumpTableCell * cell = pThisJumpTable+opcode;

    if (cell->srcState != srcState)
    {
        assert(cell->srcState == 0 || cell->srcState != srcState); // Either way means there is not outgoing edge from srcState.
        return 0;
    }
    else
    {
        return cell->destState; 
    }
}

#ifdef DEBUG

const char * CodeSeqSM::StateDesc(SM_STATE_ID stateID)
{    
    static char      s_StateDesc[500];
    static SM_OPCODE s_StateDescOpcodes[MAX_CODE_SEQUENCE_LENGTH];

    if (stateID == 0)
        return "invalid";
    
    if (stateID == SM_STATE_ID_START)
        return "start";    

    unsigned i = 0;
    
    SM_STATE_ID b = stateID; 
 
    while (States[b].prevState != 0)
    {
        s_StateDescOpcodes[i] = States[b].opc;
        b = States[b].prevState;
        ++i;
    }

    assert(i == States[stateID].length && i>0);

    * s_StateDesc = 0;
    
    while (--i>0)
    {
        strcat(s_StateDesc, smOpcodeNames[s_StateDescOpcodes[i]]);
        strcat(s_StateDesc, " -> ");
    }

    strcat(s_StateDesc, smOpcodeNames[s_StateDescOpcodes[0]]); 

    return s_StateDesc;
}

#endif // DEBUG