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/*
 * Machine specific parts of the register allocator.
 * Intel iAPX-86, SMALL and LARGE models.
 */
#ifdef   vax
#include "INC$LIB:cc1.h"
#else
#include "cc1.h"
#endif

/*
 * Select a register.
 * The argument 'tp' is the tree.
 * The argument 'c' is a context,
 * which will be either 'PAIR' or 'ANY'.
 * The 'flag' is true if ANY should be resolved.
 */
regselect(tp, c, flag)
TREE	*tp;
{
	register REGDESC	*rp;
	register KIND		kind;
	register PREGSET	busy;
	register int		byte;
	register PERTYPE	*ptp;

	ptp = &pertype[tp->t_type];
	kind = ptp->p_pair;
	byte = bytereg(tp);
	if (c != PAIR) {
		if (flag==0 && byte==0)
			return (c);
		kind = ptp->p_kind;
	}
	busy = curbusy;
	for (rp = &reg[FRREG]; rp<&reg[NRREG]; ++rp) {
		if ((rp->r_phys&busy) != 0)
			continue;
		if (c == ANYL) {
			if ((rp->r_lvalue&kind) == 0)
				continue;
		} else {
			if ((rp->r_rvalue&kind) == 0)
				continue;
		}
		if (byte && (rp->r_phys&~(BAX|BBX|BCX|BDX))!=0)
			continue;
		return (rp - &reg[0]);
	}
	return (-1);
}

/*
 * This routine returns true if register 'r'
 * is a usable temporary for tree 'tp'.
 */
isusable(tp, c, r)
register TREE	*tp;
register int	r;
{
	register int		op;
	register PERTYPE	*ptp;
	register KIND		kind;
	register int		byte;

#if !TINY
	if (sflag > 2)
		snapf("Isusable(%P, %C, %R)? ", tp, c, r);
#endif
	op = tp->t_op;
	if ((op==SHR || op==SHL || op==ASHR || op==ASHL)
	&& (reg[r].r_phys&BCX) != 0)
		goto no;
	ptp = &pertype[tp->t_type];
	if ((op>=MUL && op<=REM) || (op>=AMUL && op<=AREM))
		kind = ptp->p_pair;
	else
		kind = ptp->p_kind;
	byte = bytereg(tp);
	if (c == MLVALUE) {
		if ((reg[r].r_lvalue&kind) == 0)
			goto no;
	} else {
		if ((reg[r].r_rvalue&kind) == 0)
			goto no;
	}
	if (byte && (reg[r].r_phys&~(BAX|BBX|BCX|BDX))!=0)
		goto no;
#if !TINY
	if (sflag > 2)
		snapf("yes\n");
#endif
	return (1);
no:
#if !TINY
	if (sflag > 2)
		snapf("no\n");
#endif
	return (0);
}

/*
 * Test if a byte register is
 * needed.
 */
bytereg(tp)
register TREE *tp;
{
	register op;

	if (isbyte(tp->t_type))
		return (1);
	if ((op = tp->t_op)==LEAF || op==CONVERT || op==CAST)
		tp = tp->t_lp;
	if (isbyte(tp->t_type))
		return (1);
	if ((op==ASSIGN || (op>=AADD && op<=ASHR)) && isbyte(tp->t_lp->t_type))
		return (1);
	return (0);
}

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