Re: [hatari-devel] Debugger: instruction at PC

Hi Eero,

sorry for my late reply, I has starred the email but didn't find time to verify some things until now..

And from what you concluded that "cpureg" shows already executed
instruction and not one that's going to be executed next?

OK, I did more tests now. You're right, the first disasm instruction and the instruction which is shown by 'cpureg' really show the next instruction to be processed. The confusing part was for me, as a person used to Atari debuggers for years, that PC in this case points to the next instruction after the instruction which is about to process, i.e. two instructions in advance.

PC is always for me 'this is the next instruction'. To be fair, the debugger says "next PC" but it's really confusing, at least for the little brain of mine.

Having said all of that, there is still something fishy going on. Look at this:

> r

[...]

0000d89e: 6602 4e68 43fa 0040 3018 BNE.B #$00000002 == 0000d8a2 (TRUE)

This, according to your/my observation should say that a jump is going to happen, right? Cool. It's true. But then explain why do I see this:

0000d89e: 6602 4e68 43fa 0040 3018 BNE.B #$00000002 == 0000d8a2 (TRUE)

next PC: 0000d8a0

> d

$00d8b4 : 0c50 0000 cmpi.w #0,(a0)

$00d8b8 : 6706 beq.s $d8c0

Shouldn't be 'd' showing the jump instruction? Interestingly, it's not always reproducible. I'm attaching complete log from this session (the example above is near the end) to prove that I'm not making this up ;-)

If you were asking to show disassembly for next instruction when
when (re-)entering the debugger, does the attached patch what
you'd like to have?

I'm not sure, first I'd like to see the disasm output making sense for me ;-)

What "cpureg" shows should be correct, as it should be what
instruction CPU emulation core is going to emulate. :-)

Was "adda.l" the correct interpretation?

No it wasn't. 'addq' is the correct code, same as here:

00e15216: 5279 0000 5978 206e 0008 ADD.W #$00000001,$00005978

$e15216 : 5279 0000 5978 addq.w #1,$5978

--
MiKRO / Mystic Bytes
http://mikro.atari.org

> c Returning to emulation... 1. CPU breakpoint condition(s) matched 1 times. GemdosOpcode = 0x4b CPU=$e0123e, VBL=424, FrameCycles=70620, HBL=139, LineCycles=8, DSP=N/A > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 00e0095d A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd8 USP=00000000 ISP=00003dd8 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=0 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch 004b4e41 00e0123e: 4e41 defc 0010 2040 217c TRAP.L #$00000001 next PC: 00e01240 > d $e0123e : 4e41 trap #1 $e01240 : defc 0010 adda.w #$10,sp $e01244 : 2040 movea.l d0,a0 $e01246 : 217c 00e0 126a 0008 move.l #$e0126a,8(a0) $e0124e : 2f0b move.l a3,-(sp) $e01250 : 2f00 move.l d0,-(sp) $e01252 : 2f0b move.l a3,-(sp) $e01254 : 3f3c 0004 move.w #4,-(sp) > s CPU=$d88e, VBL=424, FrameCycles=70656, HBL=139, LineCycles=44, DSP=N/A > d $00d88e : 41fa 0052 lea $d8e2(pc),a0 $00d892 : 4a50 tst.w (a0) $00d894 : 663e bne.s $d8d4 $00d896 : 41ef 0006 lea 6(sp),a0 $00d89a : 0817 0005 btst #5,(sp) $00d89e : 6602 bne.s $d8a2 $00d8a0 : 4e68 move usp,a0 $00d8a2 : 43fa 0040 lea $d8e4(pc),a1 > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 00e0095d A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd2 USP=00000000 ISP=00003dd2 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=0 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch defc0010 0000d88e: 41fa 0052 4a50 663e 41ef LEA.L (PC,$0052) == $0000d8e2,A0 next PC: 0000d892 > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 00e0095d A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd2 USP=00000000 ISP=00003dd2 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=0 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch defc0010 0000d88e: 41fa 0052 4a50 663e 41ef LEA.L (PC,$0052) == $0000d8e2,A0 next PC: 0000d892 > s CPU=$d892, VBL=424, FrameCycles=70664, HBL=139, LineCycles=52, DSP=N/A > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 0000d8e2 A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd2 USP=00000000 ISP=00003dd2 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=0 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch 00524a50 0000d892: 4a50 663e 41ef 0006 0817 TST.W (A0) next PC: 0000d894 > d $00d892 : 4a50 tst.w (a0) $00d894 : 663e bne.s $d8d4 $00d896 : 41ef 0006 lea 6(sp),a0 $00d89a : 0817 0005 btst #5,(sp) $00d89e : 6602 bne.s $d8a2 $00d8a0 : 4e68 move usp,a0 $00d8a2 : 43fa 0040 lea $d8e4(pc),a1 $00d8a6 : 3018 move.w (a0)+,d0 > s CPU=$d894, VBL=424, FrameCycles=70672, HBL=139, LineCycles=60, DSP=N/A > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 0000d8e2 A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd2 USP=00000000 ISP=00003dd2 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=1 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch 663e41ef 0000d894: 663e 41ef 0006 0817 0005 BNE.B #$0000003e == 0000d8d4 (FALSE) next PC: 0000d896 > lock disasm Locked disasm output. > s $00d896 : 41ef 0006 lea 6(sp),a0 $00d89a : 0817 0005 btst #5,(sp) $00d89e : 6602 bne.s $d8a2 $00d8a0 : 4e68 move usp,a0 $00d8a2 : 43fa 0040 lea $d8e4(pc),a1 $00d8a6 : 3018 move.w (a0)+,d0 $00d8a8 : 0c40 0100 cmpi.w #$100,d0 $00d8ac : 6426 bcc.s $d8d4 > s $00d89a : 0817 0005 btst #5,(sp) $00d89e : 6602 bne.s $d8a2 $00d8a0 : 4e68 move usp,a0 $00d8a2 : 43fa 0040 lea $d8e4(pc),a1 $00d8a6 : 3018 move.w (a0)+,d0 $00d8a8 : 0c40 0100 cmpi.w #$100,d0 $00d8ac : 6426 bcc.s $d8d4 $00d8ae : 0c40 004b cmpi.w #$4b,d0 > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 00003dd8 A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd2 USP=00000000 ISP=00003dd2 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=1 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch 00060817 0000d89a: 0817 0005 6602 4e68 43fa BTST.B #$0005,(A7) next PC: 0000d89e > s $00d89e : 6602 bne.s $d8a2 $00d8a0 : 4e68 move usp,a0 $00d8a2 : 43fa 0040 lea $d8e4(pc),a1 $00d8a6 : 3018 move.w (a0)+,d0 $00d8a8 : 0c40 0100 cmpi.w #$100,d0 $00d8ac : 6426 bcc.s $d8d4 $00d8ae : 0c40 004b cmpi.w #$4b,d0 $00d8b2 : 660c bne.s $d8c0 > p pc Reading debugger commands from 'pc'... ERROR: No such file or directory > r D0: 00000003 D1: 00e00000 D2: 00000004 D3: 0000ffff D4: 00000008 D5: 00400000 D6: 00030002 D7: 00000000 A0: 00003dd8 A1: 00e011ea A2: 00000a87 A3: 00e023c4 A4: 000028fe A5: ffff8604 A6: ffff8606 A7: 00003dd2 USP=00000000 ISP=00003dd2 MSP=00000000 VBR=00000000 T=00 S=1 M=0 X=0 N=0 Z=0 V=0 C=0 IMASK=3 FP0: 0 FP1: 0 FP2: 0 FP3: 0 FP4: 0 FP5: 0 FP6: 0 FP7: 0 N=0 Z=0 I=0 NAN=0 prefetch 00056602 0000d89e: 6602 4e68 43fa 0040 3018 BNE.B #$00000002 == 0000d8a2 (TRUE) next PC: 0000d8a0 > d $00d8b4 : 0c50 0000 cmpi.w #0,(a0) $00d8b8 : 6706 beq.s $d8c0 $00d8ba : 0c50 0003 cmpi.w #3,(a0) $00d8be : 6614 bne.s $d8d4 $00d8c0 : d040 add.w d0,d0 $00d8c2 : d040 add.w d0,d0 $00d8c4 : d2c0 adda.w d0,a1 $00d8c6 : 4a91 tst.l (a1) > s $00d8a2 : 43fa 0040 lea $d8e4(pc),a1 $00d8a6 : 3018 move.w (a0)+,d0 $00d8a8 : 0c40 0100 cmpi.w #$100,d0 $00d8ac : 6426 bcc.s $d8d4 $00d8ae : 0c40 004b cmpi.w #$4b,d0 $00d8b2 : 660c bne.s $d8c0 $00d8b4 : 0c50 0000 cmpi.w #0,(a0)