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Debugger notes about 0x0F opcodes

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This commit is contained in:
Jeff Parsons 2015-10-30 07:58:44 -07:00
commit 03dd91cf23
2 changed files with 11 additions and 2 deletions
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2
blog/2015/10/27/README.md
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@ -79,7 +79,7 @@ XBTS (Extract Bit String) instruction -- an instruction that existed only on B0
&0654:12B9 33C0 XOR AX,AX
&0654:12BB 8BD0 MOV DX,AX
&0654:12BD B900FF MOV CX,FF00
&0654:12C0 0FA6CA INVALID ; attempt to execute an XBTS instruction
&0654:12C0 0FA6CA XBTS CX,DX,AX,CL ; attempt to execute an XBTS instruction
&0654:12C3 6658 POP EAX
&0654:12C5 8BD0 MOV DX,AX
&0654:12C7 66C1E810 SHR EAX,10

11
modules/pcjs/lib/debugger.js
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@ -1207,7 +1207,7 @@ if (DEBUGGER) {
this.maskAddr = bus.nBusLimit;
/*
* Allocate a special segment "register" for our own use, whenever a requested selector is not currently loaded
* Allocate a special segment "register", for use whenever a requested selector is not currently loaded
*/
this.segDebugger = new X86Seg(this.cpu, X86Seg.ID.DBG, "DBG");
@ -1216,6 +1216,15 @@ if (DEBUGGER) {
this.aaOpDescs = Debugger.aaOpDescs.slice();
this.aaOpDescs[0x0F] = Debugger.aOpDescUndefined;
if (this.cpu.model >= X86.MODEL_80286) {
/*
* TODO: Consider whether the aOpDesc0F table should be split in two: one for 80286-only instructions,
* and one for both 80286 and 80386. For now, the Debugger is not as strict as the X86CPU is about
* the instructions it supports for each type of CPU, in part because an 80286 machine could still be
* presented with 80386-only code that is simply "skipped over" when then CPU doesn't support it.
*
* Obviously I'm not being entirely consistent, since I don't disassemble *any* 0x0F opcodes for any
* pre-80286 CPUs. But at least I'm being up front about it.
*/
this.aaOpDescs[0x0F] = Debugger.aOpDesc0F;
if (I386 && this.cpu.model >= X86.MODEL_80386) {
this.cchReg = 8;