6502
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65816.js
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Make sure branching can't cause the program counter to go below zero 

or above 0xffff
This commit is contained in:
Preston Skupinski 2011-10-12 14:38:19 -04:00
parent 833048fefa
commit 10cd88d08e
1 changed files with 30 additions and 0 deletions
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30
cpu.js
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@ -4133,8 +4133,11 @@ var BMI = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4149,8 +4152,11 @@ var BPL = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4165,8 +4171,11 @@ var BVC = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4182,8 +4191,11 @@ var BVS = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4198,8 +4210,11 @@ var BCC = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4214,8 +4229,11 @@ var BCS = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4230,8 +4248,11 @@ var BEQ = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4246,8 +4267,11 @@ var BNE = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
}
@ -4262,8 +4286,11 @@ var BRA = {
// Handle single byte two's complement numbers as the branch argument.
if(bytes[0]<=127) {
cpu.r.pc+=bytes[0];
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=256-bytes[0];
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
};
@ -4277,8 +4304,11 @@ var BRL = {
var num = (bytes[1]<<8)|bytes[0];
if(num<=32767) {
cpu.r.pc+=num;
cpu.r.pc&=0xffff;
} else {
cpu.r.pc-=65536-num;
if(cpu.r.pc<0)
cpu.r.pc+=0xffff;
}
}
};