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v8-cpu
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Implement floating point addition 

Signed-off-by: Junjie Mao <junjie.mao@enight.me>
This commit is contained in:
Junjie Mao 2015-09-15 16:25:55 +08:00
parent bbbbf66ebb
commit e9c9ca0922
1 changed files with 41 additions and 1 deletions
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42
src/emulator/cpu.js
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@ -33,6 +33,46 @@ app.service('cpu', ['opcodes', 'memory', function(opcodes, memory) {
}
};
var findHighestBit = function(bits, max) {
var i;
for (i = max; i >= 0; i--) {
if ((bits >> i) !== 0)
break;
}
return i;
};
var floatingAdd = function(a, b) {
var a_sign = (a & 0x80) >> 7, a_expo = ((a & 0x70) >> 4), a_mant = a & 0x0F;
var b_sign = (b & 0x80) >> 7, b_expo = ((b & 0x70) >> 4), b_mant = b & 0x0F;
var a_fix = (a_mant << a_expo), b_fix = (b_mant << b_expo);
var result_sign, result_fix;
if (a_sign == b_sign) {
result_sign = a_sign;
result_fix = a_fix + b_fix;
} else {
if (a_fix > b_fix) {
result_sign = a_sign;
result_fix = a_fix - b_fix;
} else if (a_fix < b_fix) {
result_sign = b_sign;
result_fix = b_fix - a_fix;
} else {
result_fix = 0;
result_sign = 0;
}
}
var result_expo = findHighestBit(result_fix, 16) - 3;
if (result_expo > 7) {
result_expo = 7;
} else if (result_expo < 0) {
result_expo = 0;
}
var result_mant = (result_fix >> result_expo) & 0xF;
var result = (result_sign << 7) | (result_expo << 4) | result_mant;
return result;
};
self.updateTimer = false;
self.status = '';
@ -58,7 +98,7 @@ app.service('cpu', ['opcodes', 'memory', function(opcodes, memory) {
writeReg(regDest, (readReg(regSource1) + readReg(regSource2)) & 0xFF);
break;
case opcodes.ADD_FLOAT:
// TODO
writeReg(regDest, floatingAdd(readReg(regSource1), readReg(regSource2)));
break;
case opcodes.OR:
writeReg(regDest, readReg(regSource1) | readReg(regSource2));