c21.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

			/* If the bit offset is not immediate mode (i.e. $16)
			 * then we can't convert it.
			 */
			if (regs[RT1][0] != '$') goto std;

			/* Get the value of the bit offset and if it is < 0
			 * then we can't change it.
			 */
			if ((boff = getnum(&regs[RT1][1])) < 0) goto std;

			/* If the bit offset is not on an addressable unit 
			 * boundary, then we can't change it
			 */
			if ((boff % BITS_PER_UNIT) != 0) goto std; /*0001*/

			/* Calculate the chunk (addressable unit offset)
			 */
			coff = boff / BITS_PER_UNIT ;		   /*0001*/

			/* If the chunk is not zero and the extract is from
			 * a register, then we can't change it since the
			 * CVT or MOVZ can only act on the low byte or word
			 * of the register. The function isreg returns the
			 * register number or -1 if the argument is not a
			 * register.
			 */
			if (coff && (isreg(regs[RT3]) >= 0)) goto std;

			/* Determine whether to do a signed (CVT) or unsigned
			 * MOVZ operation and if the source is a byte or a
			 * word.
			 */
			p->op = (p->op == EXTV) ? CVT : MOVZ;
			p->subop = U((flen == 8 ? BYTE : WORD), LONG);

			/* Set up the source operand string in regs[RT1]
			 */
			if (coff == 0)
				/* If the addressable offset is 0 then just
				 * copy the source from RT3.
				 */
				strcpy(regs[RT1], regs[RT3]);
			else
				/* Change the source operand string to use the
				 * chunk.  If the source uses general register
				 * addressing generate "coff(Rn)" otherwise 
				 * generate "coff+address".
				 */
				sprintf(regs[RT1], "%d%s%s", coff, 
					regs[RT3][0]=='(' ? "":"+",
					regs[RT3]);

			/* Move the destination from RT4 to RT2 and set the
			 * RT3 and RT4 to null strings since we no longer need
			 * them to generate the instruction.
			 */
			strcpy(regs[RT2], regs[RT4]);
			regs[RT3][0] = '\0'; regs[RT4][0] = '\0';
			p->pop = 0; newcode(p);
		}
		nchange++;
		goto std;
	}

	case CMP:
	{
		/* comparison to -63 to -1:
		**	cmpl	r0,$-1	>	incl	r0
		**	jeql	...
		**
		**	cmpl	r0,$-63	>	addl2	$63,r0
		**	jeql	...
		*/
		register int	num;
		register int	reg;
		register struct	node	*regp = p->back;

		if (p->forw->op != CBR) goto std;
		if (p->forw->subop != JEQ && p->forw->subop != JNE) goto std;
		splitrand(p);
		if (strncmp(regs[RT2], "$-", 2) != 0) goto std;
		reg = r = isreg(regs[RT1]);
		if (r < 0) goto std;
		if (r < NUSE && uses[r] != 0) goto std;
		if (r >= NUSE && regp->op == MOV && p->subop == regp->subop)
		{
			if (*regp->code != 'r') goto std;
			reg = regp->code[1] - '0';
			if (isdigit(regp->code[2]) || reg >= NUSE || uses[reg])
				goto std;
		}
		if (r >= NUSE) goto std;
		if (reg != r)
			sprintf(regs[RT1], "r%d", reg);
		if ((num = getnum(&regs[RT2][2])) <= 0 || num > 63) goto std;
		if (num == 1)
		{
			p->op = INC; regs[RT2][0] = '\0';
		}
		else
		{
			register char	*t;

			t=regs[RT1];regs[RT1]=regs[RT2];regs[RT2]=t;
			p->op = ADD; p->subop = U(p->subop, OP2);
			for (t = &regs[RT1][2]; t[-1] = *t; t++) ;
		}
		p->pop = 0; newcode(p);
		nchange++;
		goto std;
	}

	case JSB:
		if (equstr(p->code,"mcount")) {uses[0]=p; regs[0][0]= -1;}
		goto std;
	case JBR: case JMP:
		clearuse();
		if (p->subop==RET || p->subop==RSB) {uses[0]=p; regs[0][0]= -1; break;}
		if (p->ref==0) goto std;	/* jmp (r0) */
		/* fall through */
	case CBR:
		if (p->ref->ref!=0) for (r=NUSE;--r>=0;)
			if (biti[r] & (int)p->ref->ref) {uses[r]=p; regs[r][0]= -1;}
	case EROU: case JSW:
	case TEXT: case DATA: case BSS: case ALIGN: case WGEN: case END: ;
	}
	}
	for (p= &first; p!=0; p=p->forw)
		if (p->op==LABEL || p->op==DLABEL) p->ref=0;	/* erase our tracks */
}

rmove()
{
	register struct node *p, *lastp;
	register int r;
	int r1;

	clearreg();
	for (p=first.forw; p!=0; p = p->forw) {
	lastp=p;
	if (debug) {
		printf("Regs:\n");
		for (r=0; r<NREG; r++)
			if (regs[r][0]) {
				r1=regs[r][0];
				printf("%d: %d%d %s\n", r, r1&0xF, r1>>4, regs[r]+1);
			}
		printf("-\n");
	}
	switch (p->op) {

	case CVT:
		splitrand(p); goto mov;

	case MOV:
		splitrand(p);
		if ((r = findrand(regs[RT1],p->subop)) >= 0) {
			if (r == isreg(regs[RT2]) && p->forw->op!=CBR) {
				delnode(p); redunm++; break;
			}
		}
mov:
		repladdr(p);
		r = isreg(regs[RT1]);
		r1 = isreg(regs[RT2]);
		dest(regs[RT2],p->subop);
		if (r>=0) {
			if (r1>=0) savereg(r1, regs[r]+1, p->subop);
			else if (p->op!=CVT) savereg(r, regs[RT2], p->subop);
		} else if (r1>=0) savereg(r1, regs[RT1], p->subop);
		else if (p->op!=CVT) setcon(regs[RT1], regs[RT2], p->subop);
		break;

/* .rx,.wx */
	case MFPR:
	case COM:
	case NEG:
/* .rx,.wx or .rx,.rx,.wx */
	case ADD:
	case SUB:
	case BIC:
	case BIS:
	case XOR:
	case MUL:
	case DIV:
	case ASH:
	case MOVZ:
/* .rx,.rx,.rx,.wx */
	case EXTV:
	case EXTZV:
	case INSV:
		splitrand(p);
		repladdr(p);
		dest(lastrand,p->subop);
		if (p->op==INSV) ccloc[0]=0;
		break;

/* .mx or .wx */
	case CLR:
	case INC:
	case DEC:
		splitrand(p);
		dest(lastrand,p->subop);
		if (p->op==CLR)
			if ((r = isreg(regs[RT1])) >= 0)
				savereg(r, "$0", p->subop);
			else
				setcon("$0", regs[RT1], p->subop);
		break;

/* .rx */
	case TST:
	case PUSH:
		splitrand(p);
		lastrand=regs[RT1+1]; /* fool repladdr into doing 1 operand */
		repladdr(p);
		if (p->op==TST && equstr(lastrand=regs[RT1], ccloc+1)
		  && ((0xf&(ccloc[0]>>4))==p->subop || equtype(ccloc[0],p->subop))
		  &&!source(lastrand)) {
			delnode(p); p = p->back; nrtst++; nchange++;
		}
		setcc(lastrand,p->subop);
		break;

/* .rx,.rx,.rx */
	case PROBER:
	case PROBEW:
	case CASE:
	case MOVC3:
/* .rx,.rx */
	case MTPR:
	case CALLS:
	case CMP:
	case BIT:
		splitrand(p);
		/* fool repladdr into doing right number of operands */
		if (p->op==CASE || p->op==PROBER || p->op==PROBEW) lastrand=regs[RT4];
/*		else if (p->op==CMPV || p->op==CMPZV) lastrand=regs[RT4+1]; */
		else if (p->op==MOVC3) lastrand=regs[RT1];
		else lastrand=regs[RT3];
		repladdr(p);
		if (p->op==CALLS || p->op==MOVC3) clearreg();
		if (p->op==BIT) bitopt(p);
		ccloc[0]=0; break;

	case CBR:
		if (p->subop>=JBC) {
			splitrand(p);
			if (p->subop<JBCC) lastrand=regs[RT3]; /* 2 operands can be optimized */
			else lastrand=regs[RT2]; /* .mb destinations lose */
			repladdr(p);
		}
		ccloc[0] = 0;
		break;

	case JBR:
		redunbr(p);

/* .wx,.bb */
	case SOB:

	default:
		clearreg();
	}
	}
}

char *byondrd(p) 

/* Return pointer to register which is "beyond last read/modify operand"
 */
	register struct node *p;
{
	if (OP2==(p->subop>>4))
		return(regs[RT3]);
	switch (p->op) {
		
		/* 1 operand instructions
		 */
		case JSB:
		case TST:
		case INC:
		case DEC:
		case PUSHA:
		case PUSH:	return(regs[RT2]);
		
		/* 2 operand instructions 
		 */
		case MFPR:	/* DLB0004 */
		case MTPR:
		case BIT:
		case CMP:
		case CALLS:	return(regs[RT3]);

		/* 3 operand instructions
		 */
		case PROBER:	
		case PROBEW:
		case CASE:
		case MOVC3:	return(regs[RT4]);
	}
	return(lastrand);
}

struct node *
bflow(p)
register struct node *p;
{
	register char *cp1,*cp2,**preg; register int r;
	int flow= -1;
	struct node *olduse=0;
	splitrand(p);
	if (p->op!=PUSH && p->subop && 0<=(r=isreg(lastrand)) && r<NUSE && uses[r]==p->forw) {
	if (equtype(p->subop,regs[r][0])
	|| ((p->op==CVT || p->op==MOVZ)
			 && 0xf&regs[r][0] && compat(0xf&(p->subop>>4),regs[r][0]))) {
		register int r2;
		if (regs[r][1]!=0) {/* send directly to destination */
			if (p->op==INC || p->op==DEC) {
				if (p->op==DEC) p->op=SUB; else p->op=ADD;
				p->subop=(OP2<<4)+(p->subop&0xF); /* use 2 now, convert to 3 later */
				p->pop=0;
				cp1=lastrand; cp2=regs[RT2]; while (*cp2++= *cp1++); /* copy reg */
				cp1=lastrand; *cp1++='$'; *cp1++='1'; *cp1=0;
			}
			cp1=regs[r]+1; cp2=lastrand;
			if (OP2==(p->subop>>4)) {/* use 3 operand form of instruction */
				p->pop=0;
				p->subop += (OP3-OP2)<<4; lastrand=cp2=regs[RT3];
			}
			while (*cp2++= *cp1++);
			if (p->op==MOVA && p->forw->op==PUSH) {
				p->op=PUSHA; *regs[RT2]=0; p->pop=0;
			} else if (p->op==MOV && p->forw->op==PUSH) {
				p->op=PUSH ; *regs[RT2]=0; p->pop=0;
			}
			delnode(p->forw);
			if (0<=(r2=isreg(lastrand)) && r2<NUSE) {
				uses[r2]=uses[r]; uses[r]=0;
			}
			redun3(p,0);
			newcode(p); redunm++; flow=r;
		} else if (p->op==MOV && p->forw->op!=EXTV && p->forw->op!=EXTZV) {
			/* superfluous fetch */
			int nmatch;
			char src[C2_ASIZE];
	movit:
			cp2=src; cp1=regs[RT1]; while (*cp2++= *cp1++);
			splitrand(p->forw);
			if (p->forw->op != INC && p->forw->op != DEC)
				lastrand=byondrd(p->forw);
			nmatch=0;
			for (preg=regs+RT1;*preg!=lastrand;preg++)
				if (r==isreg(*preg)) {
				cp2= *preg; cp1=src; while (*cp2++= *cp1++); ++nmatch;
			}
			if (nmatch==1) {
				if (OP2==(p->forw->subop>>4) && equstr(src,regs[RT2])) {
					p->forw->pop=0;
					p->forw->subop += (OP3-OP2)<<4; cp1=regs[RT3];
					*cp1++='r'; *cp1++=r+'0'; *cp1=0;
				}
				delnode(p); p=p->forw;
				if (0<=(r2=isreg(src)) && r2<NUSE) {
					uses[r2]=uses[r]; uses[r]=0;
				}
				redun3(p,0);
				newcode(p); redunm++; flow=r;
			} else splitrand(p);
		}
	} else if (p->op==MOV && (p->forw->op==CVT || p->forw->op==MOVZ)
		&& p->forw->subop&0xf 	/* if base or index, then forget it */
		&& compat(p->subop,p->forw->subop) && !source(cp1=regs[RT1])
		&& !indexa(cp1)) goto movit;
	}
	/* adjust 'lastrand' past any 'read' or 'modify' operands. */
	lastrand=byondrd(p);
	/* a 'write' clobbers the register. */
	if (0<=(r=isreg(lastrand)) && r<NUSE
	|| OP2==(p->subop>>4) && 0<=(r=isreg(regs[RT2])) && r<NUSE && uses[r]==0) {
		/* writing a dead register is useless, but watch side effects */
		switch (p->op) {
		case ACB:
		case AOBLEQ: case AOBLSS: case SOBGTR: case SOBGEQ: break;
		default:
			if (uses[r]==0) {/* no direct uses, check for use of condition codes */
				register struct node *q=p;
				while ((q=nonlab(q->forw))->combop==JBR) q=q->ref;	/* cc unused, unchanged */
				if (q->op!=CBR) {/* ... and destroyed */
					preg=regs+RT1;
					while (cp1= *preg++) {
						if (cp1==lastrand) {redunm++; delnode(p); return(p->forw);}
						if (source(cp1) || equstr(cp1,lastrand)) break;
					}
				}
			}
			flow=r;
		}
	}
	if (0<=(r=flow)) {olduse=uses[r]; uses[r]=0; *(short *)(regs[r])=0;}
		/* these two are here, rather than in bmove(),
		/* because I decided that it was better to go for 3-address code
		/* (save time) rather than fancy jbxx (save 1 byte)
		/* on sequences like  bisl2 $64,r0; movl r0,foo
		*/
	if (p->op==BIC) {p=bicopt(p); splitrand(p); lastrand=byondrd(p);}
	if (p->op==BIS) {bixprep(p,JBSS);           lastrand=byondrd(p);}
	/* now look for 'read' or 'modify' (read & write) uses */
	preg=regs+RT1; 
	while (*(cp1= *preg++)) {
		/* check for  r  */
		if (lastrand!=cp1 && 0<=(r=isreg(cp1)) && r<NUSE && uses[r]==0) {
			uses[r]=p; cp2=regs[r]; *cp2++=p->subop;
			if (p->op==ASH && preg==(regs+RT1+1)) cp2[-1]=BYTE; /* stupid DEC */
			if (p->op==MOV || p->op==PUSH || p->op==CVT || p->op==MOVZ || p->op==COM || p->op==NEG) {
				if (p->op==PUSH) cp1="-(sp)";
				else {
					cp1=regs[RT2];
					if (0<=(r=isreg(cp1)) && r<NUSE && uses[r]==0)
						uses[r]=olduse; /* reincarnation!! */
					/* as in  addl2 r0,r1;  movl r1,r0;  ret  */
					if (p->op!=MOV) cp1=0;
				}
				if (cp1) while (*cp2++= *cp1++);
				else *cp2=0;
			} else *cp2=0;
			continue;
		}
		/* check for (r),(r)+,-(r),[r] */
		do if (*cp1=='(' || *cp1=='[') {/* get register number */
			char t;
			cp2= ++cp1; while (*++cp1!=')' && *cp1!=']'); t= *cp1; *cp1=0;
			if (0<=(r=isreg(cp2)) && r<NUSE && (uses[r]==0 || uses[r]==p)) {
				uses[r]=p; regs[r][0]=(*--cp2=='[' ? OPX<<4 : OPB<<4);
			}
			*cp1=t;
		} while (*++cp1);
	}
	/* pushax or movax possibility? */
	cp1=regs[RT1];
	if (*cp1++=='$' && isstatic(cp1) && natural(regs[RT1])) {
		if (p->combop==T(MOV,LONG)) {
			if (regs[RT1][1]=='L' && 0!=(p->labno=getnum(regs[RT1]+2))) {
				cp1=p->code; while (*cp1++!=','); p->code= --cp1;