2.dom.c

<B>Digital的Unix操作系统VAX 4.2源码</B>

#ifndef lint
static char sccsid[] = "@(#)2.dom.c	4.1	(Berkeley)	2/11/83";
#endif not lint

#include <stdio.h>
#
/*
set dom[v] to immediate dominator of v, based on arcs as stored in inarcs
(i.e. pretending the graph is reducible if it isn't).
Algorithm is from Hecht and Ullman, Analysis of a simple algorithm for global
flow analysis problems, except bit vector operations replaced by search
through DOM to save quadratic blowup in space 
*/
#include "def.h"
#include "2.def.h"


getdom(inarc,dom)
struct list **inarc;
VERT *dom;
	{
	VERT v;
	int i;
	struct list *ls;
	for (v = 0; v < nodenum; ++v)
		dom[v] = UNDEFINED;
	for (i = 1; i < accessnum; ++i)
		{
		v = after[i];
		for (ls = inarc[v]; ls; ls = ls->nxtlist)
			{
			ASSERT(ntoaft[ls->elt] < i,getdom);
			dom[v] = comdom(dom[v],ls->elt,dom);
			}

		}
	}


comdom(u,v,dom)			/* find closest common dominator of u,v */
VERT u,v, *dom;
	{
	if (u == UNDEFINED) return(v);
	if (v == UNDEFINED) return(u);
	while(u != v)
		{
		ASSERT(u != UNDEFINED && v != UNDEFINED, comdom);
		if (ntoaft[u] < ntoaft[v])	
			v = dom[v];
		else
			u = dom[u];
		}
	return(u);
	}