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New improved PDP-10 processor flag handling

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This commit is contained in:
Jeff 2017-03-04 21:07:56 -08:00 • committed by Jeff Parsons
commit ffb7fa1221
6 changed files with 287 additions and 263 deletions
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34
modules/pdp10/lib/cpuops.js
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@ -251,7 +251,7 @@ PDP10.opILDB = function(op, acc)
* We can implement this as a simple combination of opIBP() and opLDB(), but taking care that we only call
* opIBP() on phase 1.
*/
if (this.regPS < 0) {
if (this.regBP < 0) {
//noinspection JSUnresolvedFunction
PDP10.opIBP.call(this, op, acc);
}
@ -286,14 +286,14 @@ PDP10.opLDB = function(op, acc)
* is with regEA containing the address of the bits to be loaded.
*/
var w = this.readWord(this.regEA);
if (this.regPS < 0) {
this.regPS = w;
if (this.regBP < 0) {
this.regBP = w;
this.regRA = this.regEA | PDP10.OPCODE.I_BIT;
this.advancePC(-1);
return;
}
var p = (this.regPS / PDP10.OPCODE.P_SCALE) & PDP10.OPCODE.P_MASK;
var s = (this.regPS >> PDP10.OPCODE.S_SHIFT) & PDP10.OPCODE.S_MASK;
var p = (this.regBP / PDP10.OPCODE.P_SCALE) & PDP10.OPCODE.P_MASK;
var s = (this.regBP >> PDP10.OPCODE.S_SHIFT) & PDP10.OPCODE.S_MASK;
if (p + s <= 32) {
/*
* WARNING: When using JavaScript's 32-bit operators with values that could set bit 31 and produce a
@ -310,7 +310,7 @@ PDP10.opLDB = function(op, acc)
w = Math.trunc(w / Math.pow(2, p)) % Math.pow(2, s);
}
this.writeWord(acc, w);
this.regPS = -1;
this.regBP = -1;
};
/**
@ -341,7 +341,7 @@ PDP10.opIDPB = function(op, acc)
* We can implement this as a simple combination of opIBP() and opDDB(), but taking care that we only call
* opIBP() on phase 1.
*/
if (this.regPS < 0) {
if (this.regBP < 0) {
//noinspection JSUnresolvedFunction
PDP10.opIBP.call(this, op, acc);
}
@ -376,14 +376,14 @@ PDP10.opDPB = function(op, acc)
* is with regEA containing the address of the bits to be stored.
*/
var w = this.readWord(this.regEA);
if (this.regPS < 0) {
this.regPS = w;
if (this.regBP < 0) {
this.regBP = w;
this.regRA = this.regEA | PDP10.OPCODE.I_BIT;
this.advancePC(-1);
return;
}
var p = (this.regPS / PDP10.OPCODE.P_SCALE) & PDP10.OPCODE.P_MASK;
var s = (this.regPS >> PDP10.OPCODE.S_SHIFT) & PDP10.OPCODE.S_MASK;
var p = (this.regBP / PDP10.OPCODE.P_SCALE) & PDP10.OPCODE.P_MASK;
var s = (this.regBP >> PDP10.OPCODE.S_SHIFT) & PDP10.OPCODE.S_MASK;
/*
* Regarding the SPECIAL CONSIDERATIONS above, even if the P ("shift") and/or S ("mask") values are
* over-large, we "mask" the resulting byte value (b) to 36 bits, so that when we re-assemble the final
@ -392,7 +392,7 @@ PDP10.opDPB = function(op, acc)
var b = ((this.readWord(acc) % Math.pow(2, s)) * Math.pow(2, p)) % PDP10.WORD_LIMIT;
w = (w - (w % Math.pow(2, p + s))) + b + (w % Math.pow(2, p));
this.writeWord(this.regEA, w);
this.regPS = -1;
this.regBP = -1;
};
/**
@ -1436,14 +1436,14 @@ PDP10.opASH = function(op, acc)
* If all those bits in the original value (w) were 0s, then adding bitsShifted to it could NOT
* produce a value > MAX_POS36.
*/
if (w + bitsShifted > PDP10.MAX_POS36) this.fOverflow = true;
if (w + bitsShifted > PDP10.MAX_POS36) this.regPS |= PDP10.PSFLAG.OVFL;
} else {
/*
* Since w was negative, overflow occurs ONLY if any of the bits we shifted out were 0s.
* If all those bits in the original value (w) were 1s, subtracting bitsShifted from it could NOT
* produce a value <= MAX_POS36.
*/
if (w - bitsShifted <= PDP10.MAX_POS36) this.fOverflow = true;
if (w - bitsShifted <= PDP10.MAX_POS36) this.regPS |= PDP10.PSFLAG.OVFL;
}
} else {
if (s <= -35) {
@ -1848,7 +1848,7 @@ PDP10.opPUSH = function(op, acc)
p += 0o000001000001;
this.writeWord(p & PDP10.HALF_MASK, this.readWord(this.regEA));
if (p >= PDP10.WORD_LIMIT) p -= PDP10.WORD_LIMIT;
if (!((p / PDP10.HALF_SHIFT)|0)) this.fPDOverflow = true;
if (!((p / PDP10.HALF_SHIFT)|0)) this.regPS |= PDP10.PSFLAG.PD_OVFL;
} else {
/*
* This is the SIMH behavior, which appears to increment each half of AC independently.
@ -1858,7 +1858,7 @@ PDP10.opPUSH = function(op, acc)
p = (p + 0o000001000000) - (p & PDP10.HALF_MASK) + addr;
if (p >= PDP10.WORD_LIMIT) {
p -= PDP10.WORD_LIMIT;
this.fPDOverflow = true;
this.regPS |= PDP10.PSFLAG.PD_OVFL;
}
}
this.writeWord(acc, p);
@ -1888,7 +1888,7 @@ PDP10.opPOP = function(op, acc)
if (this.regEA == acc) p = src; // this avoids re-reading the accumulator if the write just overwrote it
p -= 0o000001000001;
if (p < 0) p += PDP10.WORD_LIMIT;
if (((p / PDP10.HALF_SHIFT)|0) == PDP10.HALF_MASK) this.fPDOverflow = true;
if (((p / PDP10.HALF_SHIFT)|0) == PDP10.HALF_MASK) this.regPS |= PDP10.PSFLAG.PD_OVFL;
this.writeWord(acc, p);
};