Path: utzoo!utgpu!attcan!uunet!lll-winken!lll-tis!ames!mailrus!tut.cis.ohio-state.edu!rutgers!cmcl2!brl-adm!brl-smoke!gwyn
From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.bugs.sys5
Subject: incomplete DMD optimizer bug fix
Keywords: DMD 5620 C SGS CCS optimizer optim WE32000 3B2 bug fix
Message-ID: <8242@brl-smoke.ARPA>
Date: 28 Jul 88 19:35:34 GMT
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 31

I have discovered that the changes to the DMD 2.0 (WE32xxx) C optimizer
that I previously posted were incomplete.  In particular, an in-line
function expansion occurring as an argument in another function call
(other than the first argument) would pick up its arguments from the
wrong place.  (This is a rather rare situation.)

Some 3B C optimizers might also have this problem.

The reason I missed this earlier is that the way the code dealt with
the ops[MAXOPS] member of a NODE was extremely gross:  data of the
wrong type was being forced into this array member as a temporary
variable, rather than just having such a special member of the NODE;
in the func.c source this member was #defined as "opm", but in local.c
it was called ops[MAXOPS] (that's the one I missed when I expanded
the array by 1 to fix a problem in func.c).

Here is the bug fix, which should only be installed if you picked up
my previous changes (which changed the length of ops[] from MAXOPS+1
to MAXOPS+2).  In $DMD/sgs/usr/src/cmd/sgs/optim/m32/local.c:

/* @(#) local.c: 1.5 6/26/84				*/
...
prinst(p) register NODE *p; { /* print instruction */
...
#ifdef	IMPIL
	if (p->op == CALL ) {
		printf("@	%d	%s	%s\n", 
			numauto + ( int ) p->ops[MAXOPS+1], p->op1 + 1, p->op2 );	/* DAG -- was MAXOPS */
		p->ops[MAXOPS+1] = NULL;	/* DAG -- was MAXOPS */
	}
#endif /* IMPIL */
...