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Simplified ROT and ROTC, converting all right (negative) rotations into left (positive) rotations

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Jeff 2017-03-04 11:22:57 -08:00 • committed by Jeff Parsons
commit 20c24053b9
2 changed files with 38 additions and 45 deletions
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44
modules/pdp10/lib/cpuops.js
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@ -1382,16 +1382,16 @@ PDP10.opASH = function(op, acc)
PDP10.opROT = function(op, acc)
{
/*
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value, modulo +/-36.
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value, modulo 36 (+/-35).
*/
var s = ((this.regEA << 14) >> 24) % 36;
if (s) {
var w = this.readWord(acc);
if (s > 0) {
w = ((w * Math.pow(2, s)) % PDP10.WORD_LIMIT) + Math.trunc(w / Math.pow(2, 36 - s));
} else {
w = Math.trunc(w / Math.pow(2, -s)) + ((w * Math.pow(2, 36 + s)) % PDP10.WORD_LIMIT);
}
/*
* Note that a right rotation (s < 0) of s bits is equivalent to a left rotation (s > 0) of 36 + s bits.
*/
if (s < 0) s = 36 + s;
w = ((w * Math.pow(2, s)) % PDP10.WORD_LIMIT) + Math.trunc(w / Math.pow(2, 36 - s));
this.writeWord(acc, w);
}
};
@ -1412,7 +1412,7 @@ PDP10.opROT = function(op, acc)
PDP10.opLSH = function(op, acc)
{
/*
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value.
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value (+/-255).
*/
var s = (this.regEA << 14) >> 24;
if (s) {
@ -1475,29 +1475,23 @@ PDP10.opASHC = function(op, acc)
PDP10.opROTC = function(op, acc)
{
/*
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value.
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value, modulo 72 (+/-71).
*/
var s = ((this.regEA << 14) >> 24) % 72;
if (s) {
var wLeft = this.readWord(acc);
var wRight = this.readWord((acc + 1) & 0o17);
var wExcess = wLeft;
if (s > 0) {
if (s < 36) {
wLeft = ((wLeft * Math.pow(2, s)) % PDP10.WORD_LIMIT) + Math.trunc(wRight / Math.pow(2, 36 - s));
wRight = ((wRight * Math.pow(2, s)) % PDP10.WORD_LIMIT) + Math.trunc(wExcess / Math.pow(2, 36 - s));
} else {
wLeft = ((wRight * Math.pow(2, s - 36)) % PDP10.WORD_LIMIT) + Math.trunc(wLeft / Math.pow(2, 72 - s));
wRight = ((wExcess * Math.pow(2, s - 36)) % PDP10.WORD_LIMIT) + Math.trunc(wRight / Math.pow(2, 72 - s));
}
var wLeftOrig = wLeft;
/*
* Note that a right rotation (s < 0) of s bits is equivalent to a left rotation (s > 0) of 72 + s bits.
*/
if (s < 0) s = 72 + s;
if (s < 36) {
wLeft = ((wLeft * Math.pow(2, s)) % PDP10.WORD_LIMIT) + Math.trunc(wRight / Math.pow(2, 36 - s));
wRight = ((wRight * Math.pow(2, s)) % PDP10.WORD_LIMIT) + Math.trunc(wLeftOrig / Math.pow(2, 36 - s));
} else {
if (s > -36) {
wLeft = Math.trunc(wLeft / Math.pow(2, -s)) + ((wRight * Math.pow(2, 36 + s)) % PDP10.WORD_LIMIT);
wRight = Math.trunc(wRight / Math.pow(2, -s)) + ((wExcess * Math.pow(2, 36 + s)) % PDP10.WORD_LIMIT);
} else {
wLeft = Math.trunc(wRight / Math.pow(2, -s - 36)) + ((wLeft * Math.pow(2, 72 + s)) % PDP10.WORD_LIMIT);
wRight = Math.trunc(wExcess / Math.pow(2, -s - 36)) + ((wRight * Math.pow(2, 72 + s)) % PDP10.WORD_LIMIT);
}
wLeft = ((wRight * Math.pow(2, s - 36)) % PDP10.WORD_LIMIT) + Math.trunc(wLeft / Math.pow(2, 72 - s));
wRight = ((wLeftOrig * Math.pow(2, s - 36)) % PDP10.WORD_LIMIT) + Math.trunc(wRight / Math.pow(2, 72 - s));
}
this.writeWord(acc, wLeft);
this.writeWord((acc + 1) & 0o17, wRight);
@ -1521,7 +1515,7 @@ PDP10.opROTC = function(op, acc)
PDP10.opLSHC = function(op, acc)
{
/*
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value.
* Convert the unsigned 18-bit value in regEA to a signed 8-bit value (+/-255).
*/
var s = (this.regEA << 14) >> 24;
if (s) {