gpgx: don't let (our copy of) PC reg run away during callbacks.

todo: less ugly?

genplus-gx/cinterface/callbacks.h

@@ -9,6 +9,7 @@ extern void (*biz_execcb)(unsigned addr);
 extern void (*biz_readcb)(unsigned addr);
 extern void (*biz_writecb)(unsigned addr);
 extern CDCallback biz_cdcallback;
+extern unsigned biz_lastpc;
 
 enum eCDLog_AddrType
 {

genplus-gx/cinterface/cinterface.c

@@ -57,6 +57,7 @@ void (*biz_execcb)(unsigned addr) = NULL;
 void (*biz_readcb)(unsigned addr) = NULL;
 void (*biz_writecb)(unsigned addr) = NULL;
 CDCallback biz_cdcallback = NULL;
+unsigned biz_lastpc = 0;
 
 static void update_viewport(void)
 {
@@ -629,6 +630,8 @@ GPGX_EX int gpgx_getregs(gpregister_t *regs)
 	MAKEREG(IR);
 #undef MAKEREG
 
+	(regs-6)->value = biz_lastpc; // during read/write callbacks, PC runs away due to prefetch. restore it.
+
 	// 13
 #define MAKEREG(x) regs->name = "Z80 " #x; regs->value = Z80.x.d; regs++; ret++;
 	MAKEREG(pc);

genplus-gx/core/m68k/m68kcpu.c

@@ -342,12 +342,13 @@ void m68k_run(unsigned int cycles)
 	if (biz_execcb)
 		biz_execcb(REG_PC);
 
-		if(biz_cdcallback)
-		{
-			CDLog68k(REG_PC,eCDLog_Flags_Exec68k);
-			CDLog68k(REG_PC+1,eCDLog_Flags_Exec68k);
-		}
+	if(biz_cdcallback)
+	{
+		CDLog68k(REG_PC,eCDLog_Flags_Exec68k);
+		CDLog68k(REG_PC+1,eCDLog_Flags_Exec68k);
+	}
 
+	biz_lastpc = REG_PC;
 
     /* Decode next instruction */
     REG_IR = m68ki_read_imm_16();