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Created dedicated getOpcode() function, replaced getPCWord()

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This commit is contained in:
Jeff Parsons 2016-10-18 10:50:05 -07:00 • committed by Jeff Parsons
commit 6683c81299
3 changed files with 286 additions and 281 deletions
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35
modules/pdp11/lib/cpustate.js
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@ -560,22 +560,29 @@ CPUStatePDP11.prototype.getPC = function()
CPUStatePDP11.prototype.getLastPC = function()
{
/*
* As long as we're always snapping the PC before every opcode, we might as well use it....
* As long as we're always snapping the PC before every opcode, we might as well use it.
*/
return this.regMMR2;
};
/**
* getPCWord()
* getOpcode()
*
* TODO: Determine whether we can speed this up by *always* snapping PC into a shadow MMR2 register
* and eliminating the ABORT test.
*
* @this {CPUStatePDP11}
* @return {number}
*/
CPUStatePDP11.prototype.getPCWord = function()
CPUStatePDP11.prototype.getOpcode = function()
{
var data = this.readWord(this.regsGen[PDP11.REG.PC]);
this.advancePC(2);
return data;
var pc = this.regsGen[PDP11.REG.PC];
if (!(this.regMMR0 & PDP11.MMR0.ABORT)) {
this.regMMR1 = 0;
this.regMMR2 = pc;
}
this.regsGen[PDP11.REG.PC] = (pc + 2) & 0xffff;
return this.readWord(pc);
};
/**
@ -583,10 +590,13 @@ CPUStatePDP11.prototype.getPCWord = function()
*
* @this {CPUStatePDP11}
* @param {number} off
* @return {number} (original PC)
*/
CPUStatePDP11.prototype.advancePC = function(off)
{
this.regsGen[PDP11.REG.PC] = (this.regsGen[PDP11.REG.PC] + off) & 0xffff;
var pc = this.regsGen[PDP11.REG.PC];
this.regsGen[PDP11.REG.PC] = (pc + off) & 0xffff;
return pc;
};
/**
@ -1513,7 +1523,7 @@ CPUStatePDP11.prototype.getAddrByMode = function(mode, reg, accessFlags)
* Mode 6: d(R)
*/
case 6:
virtualAddress = this.getPCWord();
virtualAddress = this.readWord(this.advancePC(2));
virtualAddress = ((virtualAddress + this.regsGen[reg]) & 0xffff) | addrDSpace;
this.nStepCycles -= (4 + 2);
return virtualAddress;
@ -1522,7 +1532,7 @@ CPUStatePDP11.prototype.getAddrByMode = function(mode, reg, accessFlags)
* Mode 7: @d(R)
*/
case 7:
virtualAddress = this.getPCWord();
virtualAddress = this.readWord(this.advancePC(2));
virtualAddress = (virtualAddress + this.regsGen[reg]) & 0xffff;
virtualAddress = this.readWord(virtualAddress | this.addrDSpace) | addrDSpace;
this.nStepCycles -= (7 + 3);
@ -2089,18 +2099,13 @@ CPUStatePDP11.prototype.stepCPU = function(nMinCycles)
}
}
if (!(this.regMMR0 & PDP11.MMR0.ABORT)) {
this.regMMR1 = 0;
this.regMMR2 = this.regsGen[7];
}
/*
* Snapshot the TF bit in opFlags, while clearing all other opFlags (except those in PRESERVE);
* we'll check the TRAP_TF bit in opFlags when we come back around for another opcode.
*/
this.opFlags = (this.opFlags & PDP11.OPFLAG.PRESERVE) | (this.regPSW & PDP11.PSW.TF);
this.decode(this.getPCWord());
this.decode(this.getOpcode());
} while (this.nStepCycles > 0);