star.c

著名ARC模拟器源码,包括多个平台

	** If s680x0exec() is already running, then the interrupts are about
	** to get flushed anyway.  So ignore this call.
	*/
	emit("test byte[__execinfo],1\n");
	emit("jnz .noflush\n");
	/* Make registers "live" */
	emit("pushad\n");
	emit("mov esi,[__pc]\n");
	emit("xor ebp,ebp\n");
	cache_ccr();
	emit("xor edi,edi\n"); /* well, semi-live */
	emit("call flush_interrupts\n");
	emit("sub [__odometer],edi\n"); /* edi will be <= 0 here */
	emit("mov [__pc],esi\n"); /* PC guaranteed unbased */
	writeback_ccr();
	emit("popad\n");
	emit(".noflush:\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0GetContextSize()
**
**  Entry: Nothing
**  Exit:  Size of context array (in bytes)
*/
	begin_source_proc("GetContextSize");

	emit("mov eax,contextend-contextbegin\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0GetContext(context)
**
**  Entry: Address of context in EAX
**  Exit:  Nothing
*/
	begin_source_proc("GetContext");

	emit("push edx\n");
	emit("push edi\n");
	if(use_stack) emit("mov edi,[esp+12]\n");
	else          emit("mov edi,eax\n");
	emit("%%assign i 0\n");
	emit("%%rep ((contextend-contextbegin) / 8)\n");
	emit("  mov eax,[contextbegin+i+0]\n");
	emit("  mov edx,[contextbegin+i+4]\n");
	emit("  mov [edi+i+0],eax\n");
	emit("  mov [edi+i+4],edx\n");
	emit("%%assign i i+8\n");
	emit("%%endrep\n");
	emit("%%if ((contextend-contextbegin) %% 8)!=0\n");
	emit("  mov eax,[contextbegin+i+0]\n");
	emit("  mov [edi+i+0],eax\n");
	emit("%%endif\n");
	emit("pop edi\n");
	emit("pop edx\n");
	emit("xor eax,eax\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0SetContext(context)
**
**  Entry: Address of context in EAX
**  Exit:  Nothing
*/
	begin_source_proc("SetContext");

	emit("push edx\n");
	emit("push esi\n");
	if(use_stack) emit("mov esi,[esp+12]\n");
	else          emit("mov esi,eax\n");
	emit("%%assign i 0\n");
	emit("%%rep ((contextend-contextbegin) / 8)\n");
	emit("  mov eax,[esi+i+0]\n");
	emit("  mov edx,[esi+i+4]\n");
	emit("  mov [contextbegin+i+0],eax\n");
	emit("  mov [contextbegin+i+4],edx\n");
	emit("%%assign i i+8\n");
	emit("%%endrep\n");
	emit("%%if ((contextend-contextbegin) %% 8)!=0\n");
	emit("  mov eax,[esi+i+0]\n");
	emit("  mov [contextbegin+i+0],eax\n");
	emit("%%endif\n");
	emit("pop esi\n");
	emit("pop edx\n");
	emit("xor eax,eax\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0fetch(address)
**
**  (Will need to be rewritten to handle function codes)
**
**  Reads a word from memory using the _supervisor_ fetch map.
**  Entry: Address in EAX
**  Exit:  The fetched word (or -1 if the address was invalid)
*/
	begin_source_proc("fetch");

	if(use_stack) emit("mov eax,[esp+4]\n");
	emit("push ebx\n");
	emit("push esi\n");
	emit("push edi\n");/* can be destroyed by rebase */
	emit("push ebp\n");
	emit("push dword[__fetch]\n");
	emit("mov ebx,[__s_fetch]\n");
	emit("mov [__fetch],ebx\n");
	/* Must save the fetch region cache as well */
	emit("push dword[__fetch_region_start]\n");
	emit("push dword[__fetch_region_end]\n");
	/* and __execinfo */
	emit("mov bl,[__execinfo]\n");
	emit("push ebx\n");

	emit("xor ebp,ebp\n");
	emit("mov esi,eax\n");
	emit("and byte[__execinfo],0FDh\n");
	/* Force re-base */
	emit("call basefunction\n");
	emit("test byte[__execinfo],2\n");
	emit("mov eax,-1\n");
	emit("jnz short .badfetch\n");
	emit("add esi,ebp\n");
	emit("inc eax\n"); /* make eax zero */
	emit("mov ax,[esi]\n");
	emit(".badfetch:\n");
	emit("pop ebx\n");
	emit("mov [__execinfo],bl\n");
	emit("pop dword[__fetch_region_end]\n");
	emit("pop dword[__fetch_region_start]\n");
	emit("pop dword[__fetch]\n");
	emit("pop ebp\n");
	emit("pop edi\n");
	emit("pop esi\n");
	emit("pop ebx\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0readOdometer()
**
**  Reads the odometer (works from anywhere)
**  Entry: Nothing
**  Exit:  Odometer in EAX
*/
	begin_source_proc("readOdometer");

	emit("mov eax,[__cycles_needed]\n");
	emit("sub eax,[__io_cycle_counter]\n");
	emit("dec eax\n");               /* eax = elapsed cycles */
	emit("sub eax,[__cycles_leftover]\n");
	emit("add eax,[__odometer]\n");  /* add to old __odometer */
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0tripOdometer()
**
**  Reads and then clears the odometer (works from anywhere)
**  Entry: Nothing
**  Exit:  Old odometer value in EAX
*/
	begin_source_proc("tripOdometer");
	/* Read */
	emit("mov eax,[__cycles_needed]\n");
	emit("sub eax,[__io_cycle_counter]\n");
	emit("dec eax\n");               /* eax = elapsed cycles */
	emit("sub eax,[__cycles_leftover]\n");
	emit("add [__odometer],eax\n");  /* add to old __odometer */
	/* Clear */
	emit("mov eax,[__io_cycle_counter]\n");
	emit("inc eax\n");
	emit("mov [__cycles_needed],eax\n");
	emit("mov eax,[__odometer]\n");
	emit("mov dword[__odometer],0\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0controlOdometer(n)
**
**  Reads the odometer, clears it only if n != 0
**  Entry: n in EAX
**  Exit:  Old odometer value in EAX
*/
	begin_source_proc("controlOdometer");
	if(use_stack) emit("mov eax,[esp+4]\n");
	emit("or eax,eax\n");
	emit("jnz short _%stripOdometer\n", sourcename);
	emit("jmp short _%sreadOdometer\n", sourcename);

/***************************************************************************/
/*
**  s680x0releaseTimeslice()
**
**  Ends the s680x0exec call prematurely.  The early exit is reflected in
**  __odometer.
**  Entry: Nothing
**  Exit:  Nothing
*/
	begin_source_proc("releaseTimeslice");

	emit("mov eax,[__cycles_needed]\n");
	emit("sub [__io_cycle_counter],eax\n");
	emit("xor eax,eax\n");
	emit("mov [__cycles_needed],eax\n");
	emit("ret\n");

/***************************************************************************/
/*
**  s680x0readPC()
**
**  Returns the current program counter.  Works anywhere, including I/O,
**  RESET, and BKPT handlers.
**
**  Note that the value returned won't necessarily coincide exactly with the
**  beginning of an instruction.
*/
	begin_source_proc("readPC");

	emit("test byte[__execinfo],1\n");
	emit("jnz short .live\n");
	emit("mov eax,[__pc]\n");
	emit("ret\n");
	emit(".live:\n");
	emit("mov eax,[__io_fetchbased_pc]\n");
	emit("sub eax,[__io_fetchbase]\n");
	emit("ret\n");

}

/***************************************************************************/

/*
** Routine that flushes pending interrupts (with correct priority).
** Assumes "live" registers, including EDI and EBP.
**
** Does not rebase the PC.  In fact, it will un-base the PC even if there
** aren't any pending interrupts.
**
** s680x0flushInterrupts() is actually a wrapper for this.
*/
static void gen_flush_interrupts(void) {
	int cycles = (cputype == 68010) ? 46 : 44;
	align(16);
	emit("flush_interrupts:\n");
	/* Unbase PC */
	emit("sub esi,ebp\n");
	emit("xor ebp,ebp\n");
	/* This loop is intentionally post-tested because interrupt level 7
	** is non-maskable. */
	emit("mov edx,7\n");
	emit("mov cl,80h\n");
	emit("mov ch,[__sr+1]\n"); /* current PPL */
	emit("and ch,7\n");
	emit(".loop:\n");
	emit("test [__interrupts],cl\n");
	emit("jz short .noint\n");
	emit("mov dl,[__interrupts+edx]\n");
	emit("not cl\n");
	emit("and [__interrupts],cl\n");
	emit("shl edx,2\n");
	emit("call group_1_exception\n");
	emit("sub edi,byte %d\n", cycles);
	emit("jmp short .intdone\n");
	emit(".noint:\n");
	emit("dec edx\n");
	emit("jz short .intdone\n");
	emit("shr cl,1\n");
	emit("cmp dl,ch\n");
	emit("jg short .loop\n");
	emit(".intdone:\n");
	emit("ret\n");
}

/***************************************************************************/

static void ret_timing(int n) {
	if(n) {
		emit("sub edi,%s%d\n", (n < 128) ? "byte " : "", n);
	} else {
		emit("or edi,edi\n");
	}
	/* If hog mode is off, jump back to the main loop */
	if(!hog) {
		emit("jmp execend\n");
	/* If hog mode is on, fetch and execute the next instruction */
	} else {
		emit("js near execquit\n");
		emit("mov bx,[esi]\n");
		emit("add esi,byte 2\n");
		emit("jmp dword[__jmptbl+ebx*4]\n");
	}
}

/*
** This version of ret_timing does a trace flag check.
**
** Note: this only needs to be used for instructions which can potentially
**  _set_ the trace flag.  Instructions which can't set the trace flag (even
**  if they can clear it) are OK to use ret_timing as usual.  Why?  Well, if
**  an instruction is run in trace mode, that instruction is doomed to be
**  traced, regardless if it clears the trace flag during its execution.
**  Furthermore, the trace exception (being a group 1 exception after all)
**  will clear the trace tricky bit as well as the trace flag.
*/
static void ret_timing_checkpoint(int n) {
	if(n) {
		emit("sub edi,%s%d\n", (n < 128) ? "byte " : "", n);
	} else {
		emit("or edi,edi\n");
	}
	emit("jmp exec_checkpoint\n");
}

/***************************************************************************/

/* This routine decodes an extension word into EDX. */
static void gen_decode_ext(void) {
	align(16);
	emit("decode_ext:\n");
	if(cputype <= 68010) {
		emit("push ecx\n");
		emit("movzx edx,word[esi]\n");
		emit("movsx ecx,dl\n");
		emit("add esi,byte 2\n");
		emit("shr edx,12\n");
		emit("mov edx,[__reg+edx*4]\n");
		emit("jc short .long\n");
		emit("movsx edx,dx\n");
		emit(".long:\n");
		emit("add edx,ecx\n");
		emit("pop ecx\n");
		emit("ret\n");
	} else {
		/* For future expansion... */
		/* need an extra jump table here */
	}
}

/***************************************************************************/

/*
** Perform a cached rebase
*/
void perform_cached_rebase(void) {
	int myline = linenum; linenum += 2;
	emit("cmp esi,[__fetch_region_start]\n");
	emit("jb short ln%d\n", myline);
	emit("cmp esi,[__fetch_region_end]\n");
	emit("jbe short ln%d\n", myline + 1);
	emit("ln%d:\n", myline);
	emit("call basefunction\n");
	emit("ln%d:\n", myline + 1);
	emit("add esi,ebp\n");
}

/***************************************************************************/

/*
** This is the function that generates a base for a given 68K PC.
**
**  Entry: 68K PC in ESI
**  Exit:  Newly calculated base in EBP
**
** Sounds like a simple lookup into the __fetch array, and in the case of
** 32-bit addresses, it is.  But for anything less, we'll need to compensate
** for potential garbage in the unused address bits, by subtracting the value
** of these unused bits from the base.  This way the full 32 bits of the PC
** are preserved, even if they're not used.
**
** The only registers which need to be "live" here are ESI and EBP.  The
** fetch region cache is updated, and bit 1 of __execinfo is set if the base
** couldn't be calculated.
*/
static void gen_basefunction(void) {
	align(16);
	emit("basefunction:\n");
	/*
	** Prepare ESI by masking off unused address bits (but save it
	** first).
	*/
	if(addressbits < 32) {
		emit("push esi\n");
		maskaddress("esi");
	}
	emit("mov ebp,[__fetch]\n");
	emit(".check:\n");
	emit("db 3Eh\n");
	emit("cmp esi,[ebp]\n");           /* Are we smaller? */
	emit("jb short .next\n");          /* Yes, go to next address */
	emit("db 3Eh\n");
	emit("cmp esi,[ebp+4]\n");         /* Are we bigger? */
	emit("jbe short .base\n");
	emit(".next:\n");
	emit("db 3Eh\n");
	emit("cmp dword [ebp],byte -1\n"); /* End of list? */
	emit("je short .outofrange\n");
	emit("add ebp,byte 12\n");         /* To the next structure */
	emit("jmp short .check\n");
	/* Bad news... we jumped out into the weeds. */
	emit(".outofrange:\n");
	if(addressbits < 32) emit("pop esi\n");
	emit("xor ebp,ebp\n");
	emit("mov dword[__fetch_region_start],-1\n");
	emit("mov dword[__fetch_region_end],ebp\n");
	force_context_switch();
	emit("or byte[__execinfo],2\n");
	emit("ret\n");

	emit(".base:\n");
	/*
	** Dealing with addressbits < 32 again... if the unused PC bits are
	** anything but zero, then we'll need to adjust the base to
	** compensate.
	*/
	if(addressbits < 32) {
		emit("mov esi,[esp]\n");
		emit("and esi,%d\n", 0xFFFFFFFF << addressbits);
	}
	emit("push edx\n");
	emit("mov edx,ebp\n");
	/*
	** Update the fetch region cache, adding in the garbage bits where
	** applicable.
	*/
	emit("mov ebp,[edx]\n");
	if(addressbits < 32) emit("or ebp,esi\n");
	emit("mov [__fetch_region_start],ebp\n");
	emit("mov ebp,[edx+4]\n");
	if(addressbits < 32) emit("or ebp,esi\n");
	emit("mov [__fetch_region_end],ebp\n");
	emit("mov ebp,[edx+8]\n");
	emit("pop edx\n");
	if(addressbits < 32) {
		/*
		** Subtract garbage bits from the base, and restore the
		** original 32-bit PC value.
		*/
		emit("sub ebp,esi\n");
		emit("pop esi\n");
	}
	emit("ret\n");
}

/***************************************************************************/

/* Read flags from CL into our CCR.  CX is unmodified. */
static void cl2ccr(void){
	emit("mov al,cl\n");        /* read CCR -> AL */                 /* ???????????XNZVC */
	emit("mov ah,al\n");        /* copy to AH */                     /* ???XNZVC???XNZVC */
	emit("and ax,0C10h\n");     /* isolate NZ...X */                 /* 0000NZ00000X0000 */
	emit("shl ah,3\n");       /* put NZ almost where we want it */   /* 0NZ00000000X0000 */
	emit("shr al,4\n");         /* shift X flag into bit 0 */        /* 0NZ000000000000X */
	emit("mov [__xflag],al\n"); /* store X flag */                   /* 0NZ000000000000X al -> xflag */
	emit("mov al,cl\n");        /* read CCR -> AL again */           /* 0NZ00000000XNZVC */
	emit("and al,3\n");         /* isolate VC */                     /* 0NZ00000000000VC */
	emit("shr al,1\n");         /* just V */                         /* 0NZ000000000000V carry */
	emit("adc ah,ah\n");        /* append C to rest of flags */      /* NZ00000C0000000V */
}

/*
** Read flags from CX into our SR, performing a mode switch where applicable.
** CX is unmodified.  Uses 4 bytes of stack.
**
** This does not do any of the trace flag mojo, so be sure to check for it
** explicitly where applicable (hint: ret_timing_checkpoint).
*/
static void cx2sr(void){
	int myline = linenum; linenum += 2;

	emit("push ecx\n");
	/* Step 1: switch supervisor mode */
	/* Is the new mode different from the last? */
	emit("mov cl,[__sr+1]\n");
	emit("and cx,2020h\n");