xref: /netbsd-src/sys/arch/m68k/fpe/fpu_calcea.c (revision e89934bbf778a6d6d6894877c4da59d0c7835b0f)
1 /*	$NetBSD: fpu_calcea.c,v 1.26 2011/07/18 14:11:27 isaki Exp $	*/
2 
3 /*
4  * Copyright (c) 1995 Gordon W. Ross
5  * portion Copyright (c) 1995 Ken Nakata
6  * All rights reserved.
7  *
8  * Redistribution and use in source and binary forms, with or without
9  * modification, are permitted provided that the following conditions
10  * are met:
11  * 1. Redistributions of source code must retain the above copyright
12  *    notice, this list of conditions and the following disclaimer.
13  * 2. Redistributions in binary form must reproduce the above copyright
14  *    notice, this list of conditions and the following disclaimer in the
15  *    documentation and/or other materials provided with the distribution.
16  * 3. The name of the author may not be used to endorse or promote products
17  *    derived from this software without specific prior written permission.
18  * 4. All advertising materials mentioning features or use of this software
19  *    must display the following acknowledgement:
20  *      This product includes software developed by Gordon Ross
21  *
22  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
23  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
24  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
25  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
26  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
27  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
28  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
29  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
30  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
31  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
32  */
33 
34 #include "opt_m68k_arch.h"
35 
36 #include <sys/cdefs.h>
37 __KERNEL_RCSID(0, "$NetBSD: fpu_calcea.c,v 1.26 2011/07/18 14:11:27 isaki Exp $");
38 
39 #include <sys/param.h>
40 #include <sys/signal.h>
41 #include <sys/systm.h>
42 #include <machine/frame.h>
43 #include <m68k/m68k.h>
44 
45 #include "fpu_emulate.h"
46 
47 #ifdef DEBUG_FPE
48 #define DPRINTF(x)	printf x
49 #else
50 #define DPRINTF(x)	do {} while (/* CONSTCOND */ 0)
51 #endif
52 
53 /*
54  * Prototypes of static functions
55  */
56 static int decode_ea6(struct frame *, struct instruction *,
57 	struct insn_ea *, int);
58 static int fetch_immed(struct frame *, struct instruction *, int *);
59 static int fetch_disp(struct frame *, struct instruction *, int, int *);
60 static int calc_ea(struct insn_ea *, char *, char **);
61 
62 /*
63  * Helper routines for dealing with "effective address" values.
64  */
65 
66 /*
67  * Decode an effective address into internal form.
68  * Returns zero on success, else signal number.
69  */
70 int
71 fpu_decode_ea(struct frame *frame, struct instruction *insn,
72 	struct insn_ea *ea, int modreg)
73 {
74 	int sig;
75 
76 #ifdef DIAGNOSTIC
77 	if (insn->is_datasize < 0)
78 		panic("%s: called with uninitialized datasize", __func__);
79 #endif
80 
81 	sig = 0;
82 
83 	/* Set the most common value here. */
84 	ea->ea_regnum = 8 + (modreg & 7);
85 
86 	if ((modreg & 060) == 0) {
87 		/* register direct */
88 		ea->ea_regnum = modreg & 0xf;
89 		ea->ea_flags = EA_DIRECT;
90 		DPRINTF(("%s: register direct reg=%d\n",
91 		    __func__, ea->ea_regnum));
92 	} else if ((modreg & 077) == 074) {
93 		/* immediate */
94 		ea->ea_flags = EA_IMMED;
95 		sig = fetch_immed(frame, insn, &ea->ea_immed[0]);
96 		DPRINTF(("%s: immediate size=%d\n",
97 		    __func__, insn->is_datasize));
98 	}
99 	/*
100 	 * rest of the address modes need to be separately
101 	 * handled for the LC040 and the others.
102 	 */
103 #if 0 /* XXX */
104 	else if (frame->f_format == 4 && frame->f_fmt4.f_fa) {
105 		/* LC040 */
106 		ea->ea_flags = EA_FRAME_EA;
107 		ea->ea_fea = frame->f_fmt4.f_fa;
108 		DPRINTF(("%s: 68LC040 - in-frame EA (%p) size %d\n",
109 		    __func__, (void *)ea->ea_fea, insn->is_datasize));
110 		if ((modreg & 070) == 030) {
111 			/* postincrement mode */
112 			ea->ea_flags |= EA_POSTINCR;
113 		} else if ((modreg & 070) == 040) {
114 			/* predecrement mode */
115 			ea->ea_flags |= EA_PREDECR;
116 #ifdef M68060
117 #if defined(M68020) || defined(M68030) || defined(M68040)
118 			if (cputype == CPU_68060)
119 #endif
120 				if (insn->is_datasize == 12)
121 					ea->ea_fea -= 8;
122 #endif
123 		}
124 	}
125 #endif /* XXX */
126 	else {
127 		/* 020/030 */
128 		switch (modreg & 070) {
129 
130 		case 020:			/* (An) */
131 			ea->ea_flags = 0;
132 			DPRINTF(("%s: register indirect reg=%d\n",
133 			    __func__, ea->ea_regnum));
134 			break;
135 
136 		case 030:			/* (An)+ */
137 			ea->ea_flags = EA_POSTINCR;
138 			DPRINTF(("%s: reg indirect postincrement reg=%d\n",
139 			    __func__, ea->ea_regnum));
140 			break;
141 
142 		case 040:			/* -(An) */
143 			ea->ea_flags = EA_PREDECR;
144 			DPRINTF(("%s: reg indirect predecrement reg=%d\n",
145 			    __func__, ea->ea_regnum));
146 			break;
147 
148 		case 050:			/* (d16,An) */
149 			ea->ea_flags = EA_OFFSET;
150 			sig = fetch_disp(frame, insn, 1, &ea->ea_offset);
151 			DPRINTF(("%s: reg indirect with displacement reg=%d\n",
152 			    __func__, ea->ea_regnum));
153 		break;
154 
155 		case 060:			/* (d8,An,Xn) */
156 			ea->ea_flags = EA_INDEXED;
157 			sig = decode_ea6(frame, insn, ea, modreg);
158 			break;
159 
160 		case 070:			/* misc. */
161 			ea->ea_regnum = (modreg & 7);
162 			switch (modreg & 7) {
163 
164 			case 0:			/* (xxxx).W */
165 				ea->ea_flags = EA_ABS;
166 				sig = fetch_disp(frame, insn, 1,
167 				    &ea->ea_absaddr);
168 				DPRINTF(("%s: absolute address (word)\n",
169 				    __func__));
170 				break;
171 
172 			case 1:			/* (xxxxxxxx).L */
173 				ea->ea_flags = EA_ABS;
174 				sig = fetch_disp(frame, insn, 2,
175 				    &ea->ea_absaddr);
176 				DPRINTF(("%s: absolute address (long)\n",
177 				    __func__));
178 				break;
179 
180 			case 2:			/* (d16,PC) */
181 				ea->ea_flags = EA_PC_REL | EA_OFFSET;
182 				sig = fetch_disp(frame, insn, 1,
183 				    &ea->ea_absaddr);
184 				DPRINTF(("%s: pc relative word displacement\n",
185 				    __func__));
186 				break;
187 
188 			case 3:			/* (d8,PC,Xn) */
189 				ea->ea_flags = EA_PC_REL | EA_INDEXED;
190 				sig = decode_ea6(frame, insn, ea, modreg);
191 				break;
192 
193 			case 4:			/* #data */
194 				/* it should have been taken care of earlier */
195 			default:
196 				DPRINTF(("%s: invalid addr mode (7,%d)\n",
197 				    __func__, modreg & 7));
198 				return SIGILL;
199 			}
200 			break;
201 		}
202 	}
203 	ea->ea_moffs = 0;
204 
205 	return sig;
206 }
207 
208 /*
209  * Decode Mode=6 address modes
210  */
211 static int
212 decode_ea6(struct frame *frame, struct instruction *insn, struct insn_ea *ea,
213 	int modreg)
214 {
215 	int extword, idx;
216 	int basedisp, outerdisp;
217 	int bd_size, od_size;
218 	int sig;
219 
220 	extword = fusword((void *)(insn->is_pc + insn->is_advance));
221 	if (extword < 0) {
222 		return SIGSEGV;
223 	}
224 	insn->is_advance += 2;
225 
226 	/* get register index */
227 	ea->ea_idxreg = (extword >> 12) & 0xf;
228 	idx = frame->f_regs[ea->ea_idxreg];
229 	if ((extword & 0x0800) == 0) {
230 		/* if word sized index, sign-extend */
231 		idx &= 0xffff;
232 		if (idx & 0x8000) {
233 			idx |= 0xffff0000;
234 		}
235 	}
236 	/* scale register index */
237 	idx <<= ((extword >> 9) & 3);
238 
239 	if ((extword & 0x100) == 0) {
240 		/* brief extension word - sign-extend the displacement */
241 		basedisp = (extword & 0xff);
242 		if (basedisp & 0x80) {
243 			basedisp |= 0xffffff00;
244 		}
245 
246 		ea->ea_basedisp = idx + basedisp;
247 		ea->ea_outerdisp = 0;
248 		DPRINTF(("%s: brief ext word idxreg=%d, basedisp=%08x\n",
249 		    __func__, ea->ea_idxreg, ea->ea_basedisp));
250 	} else {
251 		/* full extension word */
252 		if (extword & 0x80) {
253 			ea->ea_flags |= EA_BASE_SUPPRSS;
254 		}
255 		bd_size = ((extword >> 4) & 3) - 1;
256 		od_size = (extword & 3) - 1;
257 		sig = fetch_disp(frame, insn, bd_size, &basedisp);
258 		if (sig)
259 			return sig;
260 		if (od_size >= 0)
261 			ea->ea_flags |= EA_MEM_INDIR;
262 		sig = fetch_disp(frame, insn, od_size, &outerdisp);
263 		if (sig)
264 			return sig;
265 
266 		switch (extword & 0x44) {
267 		case 0:			/* preindexed */
268 			ea->ea_basedisp = basedisp + idx;
269 			ea->ea_outerdisp = outerdisp;
270 			break;
271 		case 4:			/* postindexed */
272 			ea->ea_basedisp = basedisp;
273 			ea->ea_outerdisp = outerdisp + idx;
274 			break;
275 		case 0x40:		/* no index */
276 			ea->ea_basedisp = basedisp;
277 			ea->ea_outerdisp = outerdisp;
278 			break;
279 		default:
280 			DPRINTF(("%s: invalid indirect mode: ext word %04x\n",
281 			    __func__, extword));
282 			return SIGILL;
283 			break;
284 		}
285 		DPRINTF(("%s: full ext idxreg=%d, basedisp=%x, outerdisp=%x\n",
286 		    __func__,
287 		    ea->ea_idxreg, ea->ea_basedisp, ea->ea_outerdisp));
288 	}
289 	DPRINTF(("%s: regnum=%d, flags=%x\n",
290 	    __func__, ea->ea_regnum, ea->ea_flags));
291 	return 0;
292 }
293 
294 /*
295  * Load a value from an effective address.
296  * Returns zero on success, else signal number.
297  */
298 int
299 fpu_load_ea(struct frame *frame, struct instruction *insn, struct insn_ea *ea,
300 	char *dst)
301 {
302 	int *reg;
303 	char *src;
304 	int len, step;
305 	int sig;
306 
307 #ifdef DIAGNOSTIC
308 	if (ea->ea_regnum & ~0xF)
309 		panic("%s: bad regnum", __func__);
310 #endif
311 
312 	DPRINTF(("%s: frame at %p\n", __func__, frame));
313 	/* dst is always int or larger. */
314 	len = insn->is_datasize;
315 	if (len < 4)
316 		dst += (4 - len);
317 	step = (len == 1 && ea->ea_regnum == 15 /* sp */) ? 2 : len;
318 
319 #if 0
320 	if (ea->ea_flags & EA_FRAME_EA) {
321 		/* Using LC040 frame EA */
322 #ifdef DEBUG_FPE
323 		if (ea->ea_flags & (EA_PREDECR|EA_POSTINCR)) {
324 			printf("%s: frame ea %08x w/r%d\n",
325 			    __func__, ea->ea_fea, ea->ea_regnum);
326 		} else {
327 			printf("%s: frame ea %08x\n", __func__, ea->ea_fea);
328 		}
329 #endif
330 		src = (char *)ea->ea_fea;
331 		copyin(src + ea->ea_moffs, dst, len);
332 		if (ea->ea_flags & EA_PREDECR) {
333 			frame->f_regs[ea->ea_regnum] = ea->ea_fea;
334 			ea->ea_fea -= step;
335 			ea->ea_moffs = 0;
336 		} else if (ea->ea_flags & EA_POSTINCR) {
337 			ea->ea_fea += step;
338 			frame->f_regs[ea->ea_regnum] = ea->ea_fea;
339 			ea->ea_moffs = 0;
340 		} else {
341 			ea->ea_moffs += step;
342 		}
343 		/* That's it, folks */
344 	} else
345 #endif
346 	if (ea->ea_flags & EA_DIRECT) {
347 		if (len > 4) {
348 			DPRINTF(("%s: operand doesn't fit CPU reg\n",
349 			    __func__));
350 			return SIGILL;
351 		}
352 		if (ea->ea_moffs > 0) {
353 			DPRINTF(("%s: more than one move from CPU reg\n",
354 			    __func__));
355 			return SIGILL;
356 		}
357 		src = (char *)&frame->f_regs[ea->ea_regnum];
358 		/* The source is an int. */
359 		if (len < 4) {
360 			src += (4 - len);
361 			DPRINTF(("%s: short/byte opr - addr adjusted\n",
362 			    __func__));
363 		}
364 		DPRINTF(("%s: src %p\n", __func__, src));
365 		memcpy(dst, src, len);
366 	} else if (ea->ea_flags & EA_IMMED) {
367 		DPRINTF(("%s: immed %08x%08x%08x size %d\n", __func__,
368 		    ea->ea_immed[0], ea->ea_immed[1], ea->ea_immed[2], len));
369 		src = (char *)&ea->ea_immed[0];
370 		if (len < 4) {
371 			src += (4 - len);
372 			DPRINTF(("%s: short/byte immed opr - addr adjusted\n",
373 			    __func__));
374 		}
375 		memcpy(dst, src, len);
376 	} else if (ea->ea_flags & EA_ABS) {
377 		DPRINTF(("%s: abs addr %08x\n", __func__, ea->ea_absaddr));
378 		src = (char *)ea->ea_absaddr;
379 		copyin(src, dst, len);
380 	} else /* register indirect */ {
381 		if (ea->ea_flags & EA_PC_REL) {
382 			DPRINTF(("%s: using PC\n", __func__));
383 			reg = NULL;
384 			/*
385 			 * Grab the register contents. 4 is offset to the first
386 			 * extension word from the opcode
387 			 */
388 			src = (char *)insn->is_pc + 4;
389 			DPRINTF(("%s: pc relative pc+4 = %p\n", __func__, src));
390 		} else /* not PC relative */ {
391 			DPRINTF(("%s: using register %c%d\n",
392 			    __func__,
393 			    (ea->ea_regnum >= 8) ? 'a' : 'd',
394 			    ea->ea_regnum & 7));
395 			/* point to the register */
396 			reg = &frame->f_regs[ea->ea_regnum];
397 
398 			if (ea->ea_flags & EA_PREDECR) {
399 				DPRINTF(("%s: predecr mode - "
400 				    "reg decremented\n", __func__));
401 				*reg -= step;
402 				ea->ea_moffs = 0;
403 			}
404 
405 			/* Grab the register contents. */
406 			src = (char *)*reg;
407 			DPRINTF(("%s: reg indirect reg = %p\n", __func__, src));
408 		}
409 
410 		sig = calc_ea(ea, src, &src);
411 		if (sig)
412 			return sig;
413 
414 		copyin(src + ea->ea_moffs, dst, len);
415 
416 		/* do post-increment */
417 		if (ea->ea_flags & EA_POSTINCR) {
418 			if (ea->ea_flags & EA_PC_REL) {
419 				DPRINTF(("%s: tried to postincrement PC\n",
420 				    __func__));
421 				return SIGILL;
422 			}
423 			*reg += step;
424 			ea->ea_moffs = 0;
425 			DPRINTF(("%s: postinc mode - reg incremented\n",
426 			    __func__));
427 		} else {
428 			ea->ea_moffs += len;
429 		}
430 	}
431 
432 	return 0;
433 }
434 
435 /*
436  * Store a value at the effective address.
437  * Returns zero on success, else signal number.
438  */
439 int
440 fpu_store_ea(struct frame *frame, struct instruction *insn, struct insn_ea *ea,
441 	char *src)
442 {
443 	int *reg;
444 	char *dst;
445 	int len, step;
446 	int sig;
447 
448 #ifdef DIAGNOSTIC
449 	if (ea->ea_regnum & ~0xf)
450 		panic("%s: bad regnum", __func__);
451 #endif
452 
453 	if (ea->ea_flags & (EA_IMMED|EA_PC_REL)) {
454 		/* not alterable address mode */
455 		DPRINTF(("%s: not alterable address mode\n", __func__));
456 		return SIGILL;
457 	}
458 
459 	/* src is always int or larger. */
460 	len = insn->is_datasize;
461 	if (len < 4)
462 		src += (4 - len);
463 	step = (len == 1 && ea->ea_regnum == 15 /* sp */) ? 2 : len;
464 
465 	if (ea->ea_flags & EA_FRAME_EA) {
466 		/* Using LC040 frame EA */
467 #ifdef DEBUG_FPE
468 		if (ea->ea_flags & (EA_PREDECR|EA_POSTINCR)) {
469 			printf("%s: frame ea %08x w/r%d\n",
470 			    __func__, ea->ea_fea, ea->ea_regnum);
471 		} else {
472 			printf("%s: frame ea %08x\n", __func__, ea->ea_fea);
473 		}
474 #endif
475 		dst = (char *)ea->ea_fea;
476 		copyout(src, dst + ea->ea_moffs, len);
477 		if (ea->ea_flags & EA_PREDECR) {
478 			frame->f_regs[ea->ea_regnum] = ea->ea_fea;
479 			ea->ea_fea -= step;
480 			ea->ea_moffs = 0;
481 		} else if (ea->ea_flags & EA_POSTINCR) {
482 			ea->ea_fea += step;
483 			frame->f_regs[ea->ea_regnum] = ea->ea_fea;
484 			ea->ea_moffs = 0;
485 		} else {
486 			ea->ea_moffs += step;
487 		}
488 		/* That's it, folks */
489 	} else if (ea->ea_flags & EA_ABS) {
490 		DPRINTF(("%s: abs addr %08x\n", __func__, ea->ea_absaddr));
491 		dst = (char *)ea->ea_absaddr;
492 		copyout(src, dst + ea->ea_moffs, len);
493 		ea->ea_moffs += len;
494 	} else if (ea->ea_flags & EA_DIRECT) {
495 		if (len > 4) {
496 			DPRINTF(("%s: operand doesn't fit CPU reg\n",
497 			    __func__));
498 			return SIGILL;
499 		}
500 		if (ea->ea_moffs > 0) {
501 			DPRINTF(("%s: more than one move to CPU reg\n",
502 			    __func__));
503 			return SIGILL;
504 		}
505 		dst = (char *)&frame->f_regs[ea->ea_regnum];
506 		/* The destination is an int. */
507 		if (len < 4) {
508 			dst += (4 - len);
509 			DPRINTF(("%s: short/byte opr - dst addr adjusted\n",
510 			    __func__));
511 		}
512 		DPRINTF(("%s: dst %p\n", __func__, dst));
513 		memcpy(dst, src, len);
514 	} else /* One of MANY indirect forms... */ {
515 		DPRINTF(("%s: using register %c%d\n", __func__,
516 		    (ea->ea_regnum >= 8) ? 'a' : 'd', ea->ea_regnum & 7));
517 		/* point to the register */
518 		reg = &(frame->f_regs[ea->ea_regnum]);
519 
520 		/* do pre-decrement */
521 		if (ea->ea_flags & EA_PREDECR) {
522 			DPRINTF(("%s: predecr mode - reg decremented\n",
523 			    __func__));
524 			*reg -= step;
525 			ea->ea_moffs = 0;
526 		}
527 
528 		/* calculate the effective address */
529 		sig = calc_ea(ea, (char *)*reg, &dst);
530 		if (sig)
531 			return sig;
532 
533 		DPRINTF(("%s: dst addr=%p+%d\n", __func__, dst, ea->ea_moffs));
534 		copyout(src, dst + ea->ea_moffs, len);
535 
536 		/* do post-increment */
537 		if (ea->ea_flags & EA_POSTINCR) {
538 			*reg += step;
539 			ea->ea_moffs = 0;
540 			DPRINTF(("%s: postinc mode - reg incremented\n",
541 			    __func__));
542 		} else {
543 			ea->ea_moffs += len;
544 		}
545 	}
546 
547 	return 0;
548 }
549 
550 /*
551  * fetch_immed: fetch immediate operand
552  */
553 static int
554 fetch_immed(struct frame *frame, struct instruction *insn, int *dst)
555 {
556 	int data, ext_bytes;
557 
558 	ext_bytes = insn->is_datasize;
559 
560 	if (0 < ext_bytes) {
561 		data = fusword((void *)(insn->is_pc + insn->is_advance));
562 		if (data < 0)
563 			return SIGSEGV;
564 		if (ext_bytes == 1) {
565 			/* sign-extend byte to long */
566 			data &= 0xff;
567 			if (data & 0x80)
568 				data |= 0xffffff00;
569 		} else if (ext_bytes == 2) {
570 			/* sign-extend word to long */
571 			data &= 0xffff;
572 			if (data & 0x8000)
573 			data |= 0xffff0000;
574 		}
575 		insn->is_advance += 2;
576 		dst[0] = data;
577 	}
578 	if (2 < ext_bytes) {
579 		data = fusword((void *)(insn->is_pc + insn->is_advance));
580 		if (data < 0)
581 			return SIGSEGV;
582 		insn->is_advance += 2;
583 		dst[0] <<= 16;
584 		dst[0] |= data;
585 	}
586 	if (4 < ext_bytes) {
587 		data = fusword((void *)(insn->is_pc + insn->is_advance));
588 		if (data < 0)
589 			return SIGSEGV;
590 		dst[1] = data << 16;
591 		data = fusword((void *)(insn->is_pc + insn->is_advance + 2));
592 		if (data < 0)
593 			return SIGSEGV;
594 		insn->is_advance += 4;
595 		dst[1] |= data;
596 	}
597 	if (8 < ext_bytes) {
598 		data = fusword((void *)(insn->is_pc + insn->is_advance));
599 		if (data < 0)
600 			return SIGSEGV;
601 		dst[2] = data << 16;
602 		data = fusword((void *)(insn->is_pc + insn->is_advance + 2));
603 		if (data < 0)
604 			return SIGSEGV;
605 		insn->is_advance += 4;
606 		dst[2] |= data;
607 	}
608 
609 	return 0;
610 }
611 
612 /*
613  * fetch_disp: fetch displacement in full extension words
614  */
615 static int
616 fetch_disp(struct frame *frame, struct instruction *insn, int size, int *res)
617 {
618 	int disp, word;
619 
620 	if (size == 1) {
621 		word = fusword((void *)(insn->is_pc + insn->is_advance));
622 		if (word < 0)
623 			return SIGSEGV;
624 		disp = word & 0xffff;
625 		if (disp & 0x8000) {
626 			/* sign-extend */
627 			disp |= 0xffff0000;
628 		}
629 		insn->is_advance += 2;
630 	} else if (size == 2) {
631 		word = fusword((void *)(insn->is_pc + insn->is_advance));
632 		if (word < 0)
633 			return SIGSEGV;
634 		disp = word << 16;
635 		word = fusword((void *)(insn->is_pc + insn->is_advance + 2));
636 		if (word < 0)
637 			return SIGSEGV;
638 		disp |= (word & 0xffff);
639 		insn->is_advance += 4;
640 	} else {
641 		disp = 0;
642 	}
643 	*res = disp;
644 	return 0;
645 }
646 
647 /*
648  * Calculates an effective address for all address modes except for
649  * register direct, absolute, and immediate modes.  However, it does
650  * not take care of predecrement/postincrement of register content.
651  * Returns a signal value (0 == no error).
652  */
653 static int
654 calc_ea(struct insn_ea *ea, char *ptr, char **eaddr)
655 	/* ptr:		 base address (usually a register content) */
656 	/* eaddr:	 pointer to result pointer */
657 {
658 	int data, word;
659 
660 	DPRINTF(("%s: reg indirect (reg) = %p\n", __func__, ptr));
661 
662 	if (ea->ea_flags & EA_OFFSET) {
663 		/* apply the signed offset */
664 		DPRINTF(("%s: offset %d\n", __func__, ea->ea_offset));
665 		ptr += ea->ea_offset;
666 	} else if (ea->ea_flags & EA_INDEXED) {
667 		DPRINTF(("%s: indexed mode\n", __func__));
668 
669 		if (ea->ea_flags & EA_BASE_SUPPRSS) {
670 			/* base register is suppressed */
671 			ptr = (char *)ea->ea_basedisp;
672 		} else {
673 			ptr += ea->ea_basedisp;
674 		}
675 
676 		if (ea->ea_flags & EA_MEM_INDIR) {
677 			DPRINTF(("%s: mem indir mode: basedisp=%08x, "
678 			    "outerdisp=%08x\n",
679 			    __func__, ea->ea_basedisp, ea->ea_outerdisp));
680 			DPRINTF(("%s: addr fetched from %p\n", __func__, ptr));
681 			/* memory indirect modes */
682 			word = fusword(ptr);
683 			if (word < 0)
684 				return SIGSEGV;
685 			word <<= 16;
686 			data = fusword(ptr + 2);
687 			if (data < 0)
688 				return SIGSEGV;
689 			word |= data;
690 			DPRINTF(("%s: fetched ptr 0x%08x\n", __func__, word));
691 			ptr = (char *)word + ea->ea_outerdisp;
692 		}
693 	}
694 
695 	*eaddr = ptr;
696 
697 	return 0;
698 }
699