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CPM OPERATING SYSTEMS/CPM 68K/1.0X SOURCES/v102a/c168/sucomp.c.1

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+/*
+	Copyright 1982
+	Alcyon Corporation
+	8716 Production Ave.
+	San Diego, Ca.  92121
+
+	@(#)sucomp.c	1.3	11/2/83
+*/
+
+#include "cgen.h"
+#include "cskel.h"
+
+
+/* sucomp - Sethy-Ullman expression complexity measure computation*/
+/*		This is a heuristic computation of the Sethy-Ullman numbers*/
+/*		for expressions.  This gives an approximation of the complexity*/
+/*		of the expression.  The code generation scheme works best if*/
+/*		the most complex expressions are done first.*/
+sucomp(tp,nregs,flag)				/* returns - none*/
+struct tnode *tp;					/* pointer to tree*/
+int nregs;							/* number of registers left*/
+int flag;							/* 1=>set values in tree, 0=>return*/
+{
+	register short su, sur, op, i;
+	register struct tnode *ltp, *rtp;
+
+	nregs = DREG(nregs);
+	if( BINOP(op=tp->t_op) ) {
+		ltp = tp->t_left;
+		rtp = tp->t_right;
+	}
+	else if( UNARYOP(op) )
+		ltp = tp->t_left;
+	switch( op ) {
+
+	case CLONG:
+		if( tp->t_lvalue >= 0x8000L || tp->t_lvalue <= 0xffff8000L ) {
+			su = SU_ADDR;
+			break;
+		}
+		i = tp->t_lvalue;
+	case CINT:
+		if( op == CINT )
+			i = tp->t_value;
+		if( i == 0 )
+			su = SU_ZERO;
+		else if( i == 1 )
+			su = SU_ONE;
+		else if( i >= 1 && i <= QUICKVAL )
+			su = SU_SMALL;
+		else if( i >= -128 && i <= 127 )
+			su = SU_QUICK;
+		else
+			su = SU_CONST;
+		break;
+
+	case COMMA:
+		su = sucomp(rtp,nregs,flag);
+		i = sucomp(ltp,nregs,flag);
+		su = MAX(su,i);
+		su = MAX(su,SU_EASY);
+		break;
+
+	case ADDR:
+		su = sucomp(ltp,nregs,flag);
+		break;
+
+	case CFLOAT:
+	case DCLONG:
+	case AUTOINC:
+	case AUTODEC:
+		su = SU_ADDR;
+		break;
+
+	case SYMBOL:
+		if( tp->t_sc != REGISTER )
+			su = SU_ADDR;
+		else if( ISDREG(tp->t_reg) )
+			su = SU_REG;
+		else
+			su = SU_AREG;
+		break;
+
+	case LDIV:
+	case LMOD:
+	case LMULT:
+	case CALL:
+		sucomp(rtp,nregs,flag);
+	case NACALL:
+		sucomp(ltp,nregs,flag);
+		su = SU_VHARD;				/*very hard*/
+		break;
+
+	default:
+		su = sucomp(ltp,nregs,flag);
+		if( BINOP(op) ) {
+			if( su <= SU_ADDR ) {
+				i = sucomp(rtp,nregs,flag);
+				su = MAX(su,i);
+			}
+			else {
+				sur = sucomp(rtp,nregs+1,flag);
+				if( sur > SU_ADDR && nregs > HICREG )
+					su = MAX(su,SU_HARD);
+			}
+			su = MAX(SU_EASY,su);
+		}
+		else if( su <= SU_XREG )
+			su = MAX(SU_EASY,su);
+		if( ISFLOAT(tp->t_type) )
+			su = SU_VHARD;
+		break;
+	}
+	if( flag )
+		tp->t_su = su;
+	return(su);
+}