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Cleaned up conditional jump handling

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This commit is contained in:
Jeff Parsons 2015-05-04 19:26:06 -07:00 • committed by jeffpar
commit 2784934491
10 changed files with 135 additions and 50 deletions
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51
modules/pcjs/lib/x86op0f.js
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@ -342,6 +342,23 @@ X86.opMOVcr = function MOVcr()
}
};
/*
* NOTE: The following 16 new conditional jumps actually rely on the OPERAND override setting
* for determining whether a signed 16-bit or 32-bit displacement will be fetched, even though
* the ADDRESS override might seem more intuitive. Think of them as instructions that are loading
* a new operand into IP/EIP.
*
* Also, in 16-bit code, even though a signed rel16 value would seem to imply a range of -32768
* to +32767, any location within a 64Kb code segment outside that range can be reached by choosing
* a displacement in the opposite direction, causing the 16-bit value in EIP to underflow or overflow;
* any underflow or overflow doesn't matter, because only the low 16 bits of EIP are used when a
* 16-bit OPERAND size is in effect.
*
* In fact, for 16-bit jumps, it's simpler to always think of rel16 as an UNSIGNED value added to
* the current EIP, where the result is then truncated to a 16-bit value. This is why we don't have
* to sign-extend rel16 before adding it to the current EIP.
*/
/**
* opJOw()
*
@ -351,7 +368,7 @@ X86.opMOVcr = function MOVcr()
*/
X86.opJOw = function JOw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getOF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -369,7 +386,7 @@ X86.opJOw = function JOw()
*/
X86.opJNOw = function JNOw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getOF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -387,7 +404,7 @@ X86.opJNOw = function JNOw()
*/
X86.opJCw = function JCw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getCF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -405,7 +422,7 @@ X86.opJCw = function JCw()
*/
X86.opJNCw = function JNCw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getCF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -423,7 +440,7 @@ X86.opJNCw = function JNCw()
*/
X86.opJZw = function JZw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getZF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -441,7 +458,7 @@ X86.opJZw = function JZw()
*/
X86.opJNZw = function JNZw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getZF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -459,7 +476,7 @@ X86.opJNZw = function JNZw()
*/
X86.opJBEw = function JBEw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getCF() || this.getZF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -477,7 +494,7 @@ X86.opJBEw = function JBEw()
*/
X86.opJNBEw = function JNBEw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getCF() && !this.getZF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -495,7 +512,7 @@ X86.opJNBEw = function JNBEw()
*/
X86.opJSw = function JSw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getSF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -513,7 +530,7 @@ X86.opJSw = function JSw()
*/
X86.opJNSw = function JNSw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getSF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -531,7 +548,7 @@ X86.opJNSw = function JNSw()
*/
X86.opJPw = function JPw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getPF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -549,7 +566,7 @@ X86.opJPw = function JPw()
*/
X86.opJNPw = function JNPw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getPF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -567,7 +584,7 @@ X86.opJNPw = function JNPw()
*/
X86.opJLw = function JLw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getSF() != !this.getOF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -585,7 +602,7 @@ X86.opJLw = function JLw()
*/
X86.opJNLw = function JNLw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getSF() == !this.getOF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -603,7 +620,7 @@ X86.opJNLw = function JNLw()
*/
X86.opJLEw = function JLEw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (this.getZF() || !this.getSF() != !this.getOF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -621,7 +638,7 @@ X86.opJLEw = function JLEw()
*/
X86.opJNLEw = function JNLEw()
{
var disp = this.getIPDispWord();
var disp = this.getIPWord();
if (!this.getZF() && !this.getSF() == !this.getOF()) {
this.setIP(this.getIP() + disp);
this.nStepCycles -= this.cycleCounts.nOpCyclesJmpC;
@ -1301,7 +1318,7 @@ X86.aOps0F[0x06] = X86.opCLTS;
/*
* On all processors (except the 8086/8088, of course), X86.OPCODE.UD2 (0x0F,0x0B), aka "UD2", is an
* instruction guaranteed to raise a #UD (Invalid Opcode) exception (INT 0x06) on all future x86 processors.
* instruction guaranteed to raise a #UD (Invalid Opcode) exception (INT 0x06) on all post-8086 processors.
*/
X86.aOps0F[0x0B] = X86.opInvalid;