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Handle wrap-around for 16-bit real-mode POPs as well

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Jeff 2017-07-20 12:13:08 -07:00 • committed by Jeff Parsons
commit fb493d09ac
8 changed files with 548 additions and 522 deletions
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65
modules/pcx86/lib/x86cpu.js
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@ -3779,32 +3779,60 @@ class X86CPU extends CPU {
var w = this.getWord(this.regLSP);
this.regLSP = (this.regLSP + (I386? this.sizeData : 2))|0;
/*
* Properly comparing regLSP to regLSPLimit would normally require coercing both to unsigned
* (ie, floating-point) values. But instead, we do a subtraction, (regLSPLimit - regLSP), and
* if the result is negative, we need only be concerned if the signs of both numbers are the same
* (ie, the sign of their XOR'ed union is positive).
* (ie, floating-point) values. But instead, we subtract them, and if the delta is negative,
* we need only be concerned if the signs of both numbers are the same (ie, the sign of their
* XOR'ed union is positive).
*
* TODO: I'm combining the old 8088 address-wrap check with the new segment-limit check,
* even though the correct time to do the latter is immediately BEFORE the fetch, not AFTER;
* I'm working around this for now by applying a -1 fudge factor to the fault check below.
*/
var off = ((this.regLSPLimit - this.regLSP)|0);
if (off < 0 && (this.regLSPLimit ^ this.regLSP) >= 0) {
var delta = (this.regLSPLimit - this.regLSP)|0;
if (delta < 0 && (this.regLSPLimit ^ this.regLSP) >= 0) {
/*
* There's no such thing as an SS fault on the 8086/8088, and I'm assuming that, on newer
* processors, when the stack segment limit is set to the maximum, it's OK for the stack to wrap.
* There's no such thing as an SS fault on the 8086/8088, and in fact, we have to support the
* operation even when the address straddles the wrap boundary; other emulators tend to barf on
* a wrap, usually because they're running in V86 mode instead of real mode.
*/
if (this.model <= X86.MODEL_8088 || !this.segSS.fExpDown && this.segSS.limit == this.segSS.maskAddr || this.segSS.fExpDown && !this.segSS.limit) {
if (this.model <= X86.MODEL_8088) {
this.setSP((this.regLSP - this.segSS.base) & this.segSS.maskAddr);
} else if (off < -1) { // fudge factor
X86.helpFault.call(this, X86.EXCEPTION.SS_FAULT, 0);
if (delta < -1) {
w = (w & 0xff) | (this.getByte(this.regLSP - 1) << 8);
}
}
else {
/*
* I'm assuming that, on newer processors, when the stack segment limit is set to the maximum,
* it's OK for the stack to wrap, unless the new address is straddling the wrap boundary (ie, when
* delta is < 0 and > -sizeData).
*/
if (!this.segSS.fExpDown && this.segSS.limit == this.segSS.maskAddr || this.segSS.fExpDown && !this.segSS.limit) {
this.setSP((this.regLSP - this.segSS.base) & this.segSS.maskAddr);
} else if (delta < -1) { // fudge factor
X86.helpFault.call(this, X86.EXCEPTION.SS_FAULT, 0);
}
}
}
return w;
}
/**
* pushWord(w)
*
* NOTE: pushWord() used to do a simplfied version of pushData(), and while that might have made the emulator
* slightly faster, it was woefully duplicative. Let's trust the combination of the Closure Compiler and the
* JavaScript engines to automatically inline instead.
*
* @this {X86CPU}
* @param {number} w is the word (16-bit) value to push at current SP; SP decreased by 2 or 4
*/
pushWord(w)
{
this.pushData(w, I386? this.sizeData : 2);
}
/**
* pushData(data, width, size)
*
@ -3892,21 +3920,6 @@ class X86CPU extends CPU {
this.regLSP = regLSP;
}
/**
* pushWord(w)
*
* NOTE: pushWord() used to do a simplfied version of pushData(), and while that might have made the emulator
* slightly faster, it was woefully duplicative. Let's trust the combination of the Closure Compiler and the
* JavaScript engines to automatically inline instead.
*
* @this {X86CPU}
* @param {number} w is the word (16-bit) value to push at current SP; SP decreased by 2 or 4
*/
pushWord(w)
{
this.pushData(w, I386? this.sizeData : 2);
}
/**
* checkINTR()
*