/*
 * 68K/386 32-bit C compiler.
 *
 * copyright (c) 1996, David Lindauer
 * 
 * This compiler is intended for educational use.  It may not be used
 * for profit without the express written consent of the author.
 *
 * It may be freely redistributed, as long as this notice remains intact
 * and sources are distributed along with any executables derived from them.
 *
 * The author is not responsible for damages, either direct or consequential,
 * that may arise from use of this software.
 *
 * V1.85 July 2000
 * David Lindauer, gclind01@starbase.spd.louisville.edu
 *
 * Credits to Mathew Brandt for original K&R C compiler
 *
 */
/*
 * icom.c
 *
 * Collect common code sequences
 *
 */
#include        <stdio.h>
#include				<malloc.h>
#include 				<string.h>
#include        "lists.h"
#include				"utype.h"	
#include				"cmdline.h"	
#include        "expr.h"
#include        "c.h"
#include				"iexpr.h"
#include				"iopt.h"

extern int firstlabel;
extern int prm_optcode;
extern int nextlabel;

COMGOREC **matches;

/* Make a list of all gotos */
static COMGOREC *find_goto(QUAD *q, int label)
{
	COMGOREC *rv;
	QUAD *tail;
	int stmt = 0;
	while (!stmt && q) {
		if (!q)
			return 0;
		/* Find us a goto with this label */
		while (q && (q->dc.opcode != i_goto || q->dc.label != label)) {
			q = q->fwd;
			if (!q)
				return 0;
		}
		/* Now find the span of possibly common expressions associated
	   * with this goto 
		 */
		tail = q;
		q = q->back;
		while (q) {
			switch (q->dc.opcode) {
				case i_goto:
				case i_jc:
				case i_jnc:
				case i_jbe:
				case i_ja:
				case i_je:
				case i_jne:
				case i_jge:
				case i_jg:
				case i_jle:
				case i_jl:
				case i_dc:
				case i_label:
				case i_coswitch:
					q = q->fwd->fwd;
					goto done;
				default:
					stmt++;
				case i_line:
				case i_block:
				case i_passthrough:
					if (!q->back)
						goto done;
					q = q->back;
					break;
			}
		}
done:
		if (!stmt)
			q = tail->fwd;
	}
	/* Link the goto into the chain */
	if (stmt == 0)
		return 0;
	rv = xalloc(sizeof(COMGOREC));
	rv->tail = tail;
	q = q->back;
	rv->head = q;
	rv->size = stmt;
	return rv;
}
/* See if two quads are equal */
static int equalquad(QUAD *stail, QUAD *dtail)
{
		switch (stail->dc.opcode) {
			case i_ret: case i_rett: case i_genword:
			case i_cppini: case i_parmadj:
				return 1;
 			case i_jc: case i_ja: case i_je: case i_jnc: case i_jbe:
 			case i_jne: case i_jl: case i_jg: case i_jle: case i_jge:
				if (!equalimode(stail->dc.left,dtail->dc.left))
					return 0;
	 		case i_sub: case i_udiv: case i_umod: case i_sdiv: case i_smod:
 			case i_lsl: case i_lsr: case i_asl: case i_asr:
				return equalimode(stail->dc.left,dtail->dc.left) && equalimode(stail->dc.right,dtail->dc.right);

			case i_add: case i_umul: case i_smul:
 			case i_and: case i_or: case i_eor:
				if (equalimode(stail->dc.left,dtail->dc.left) && equalimode(stail->dc.right,dtail->dc.right))
					return 1;
				return equalimode(stail->dc.left,dtail->dc.right) && equalimode(stail->dc.right,dtail->dc.left);

			case i_parm:
 			case i_parmblock: 
 			case i_trap: case i_int:
 			case i_goto: case i_gosub:
 			case i_setnz: case i_neg: case i_not:
				return equalimode(stail->dc.left,dtail->dc.left);

			case i_assnblock: 
	 		case i_assn:
				return equalimode(stail->dc.left,dtail->dc.left) && equalimode(stail->ans,dtail->ans);
			default:
				return 0;
		}
}
/* 
 * Compare two goto groups for matches
 * and return length of match
 */
static int compare(COMGOREC *dest, COMGOREC *source)
{
	int i,rv=0;
	QUAD *dtail,*stail;
	dtail = dest->tail->back;
	stail = source->tail->back;	
	for (i=0; i < dest->size; i++) {
		/* Ignoring block and line statements */
		while(dtail && (dtail->dc.opcode == i_block || dtail->dc.opcode == i_line ||dtail->dc.opcode == i_passthrough ||dtail->dc.opcode == i_label))
			dtail = dtail->back;
		while(stail && (stail->dc.opcode == i_block || stail->dc.opcode == i_line || stail->dc.opcode == i_passthrough))
			stail = stail->back;
		/* Check for match */
		if (!dtail || !stail)
			return rv;
		if (stail->dc.opcode != dtail->dc.opcode)
			return rv;
		if (!equalquad(stail,dtail))
			return rv;
		rv++;
		dtail = dtail->back;
		stail = stail->back;
	}
	return rv;
}
/* Run through a single label lookin for common expressions
 *
 * Note that this routine may generate new labels, which will eventually
 * themselves be scanned
 */
static void runone(QUAD *q, int label)
{
	int lcount = 0,lbl;
	COMGOREC *t,work;
	QUAD *h = q;
	/* Collect all goto statements */
	while (h&&((t = find_goto(h,label)) != 0)) {
		matches[lcount++] = t;
		h = t->tail->fwd;
	}
  /* Quit if none */
	if (lcount < 2)
		return;
	do {
		int i,count;
		lbl = -1;

		/* Scan for matches and insert them.
	   * we WILL be scanning backwords to keep jumps forward as often as
     * possible
		 */
		t = matches[--lcount];
		for (i=0; i <lcount; i++) {
			if ((count=compare(t,matches[i])) != 0){
				int qcount = count;
				work = *t;
				/* Create descriptors for the match */
				if (count != matches[i]->size) {
					matches[i]->head = matches[i]->tail;
					while (count--) {
						matches[i]->head = matches[i]->head->back;
						while (matches[i]->head->dc.opcode == i_block || matches[i]->head->dc.opcode == i_line || matches[i]->head->dc.opcode == i_label
									|| matches[i]->head->dc.opcode == i_passthrough)
							matches[i]->head = matches[i]->head->back;
					}	
				}
				if (qcount != work.size) {
					work.head = work.tail;
					while (qcount--) {
						work.head = work.head->back;
						while (work.head->dc.opcode == i_block || work.head->dc.opcode == i_line || work.head->dc.opcode == i_label || work.head->dc.opcode == i_passthrough)
							work.head = work.head->back;
					}	
				}
				/* Make sure we are not at the start */
				if (matches[i]->head->back) {
					QUAD *gq = xalloc(sizeof(QUAD));
					QUAD *lq = xalloc(sizeof(QUAD));
					lbl = nextlabel++;
					/* insert a new goto statement */
					gq->dc.opcode = i_goto;
					gq->dc.right = gq->ans = gq->dc.left = 0;
					gq->dc.label = lbl; 
					gq->fwd = matches[i]->tail->fwd;
					gq->back = matches[i]->head->back;
					/* dead code deletion */
					matches[i]->head->back->fwd = gq;
					matches[i]->tail->fwd->back = gq;
					matches[i--] = matches[--lcount];
					/* put in a label */
					lq->dc.opcode = i_label;
					lq->dc.right = lq->ans = lq->dc.left = 0;
					lq->dc.label = lbl;
					lq->fwd = work.head;
					lq->back = work.head->back;
					work.head->back->fwd = lq;
					work.head->back = lq;
				}
			}
		}
	} while (lcount > 1 && lbl != -1);
}
/* Main routine for common code deletion */
void commondelete(QUAD *quad)
{
  int label;
	if (!prm_optcode)
		return;
	for (label = firstlabel; label < nextlabel; label++) {
		matches = oalloc((nextlabel - firstlabel) * sizeof(COMGOREC *));
		runone(quad,label);
		release_opt();
	}
}
