Path: utzoo!utgpu!watmath!att!chinet!pdg
From: pdg@chinet.chi.il.us (Paul Guthrie)
Newsgroups: comp.lang.c
Subject: long conversion of short expression.
Message-ID: <9092@chinet.chi.il.us>
Date: 27 Jul 89 22:41:34 GMT
Reply-To: pdg@chinet.chi.il.us (Paul Guthrie)
Organization: The League of Crafty Hackers
Lines: 27

Here is a case where 68000 compilers don't seem to agree. 
In the following code segment, the two shorts multiplied together
exceed the size of a short, but the question is, is the result
of the multiplication really a short to be converted to a
long, or a long already?

        main()
        {

                short x=0x18,y=0x588;
                long z=0x100000;
                printf("%lx\n",z+(x*y));
        }
 
Should the compiler generate
	move -2(fp),d0
	muls -4(fp),d0
	extl d0
	addl -8(fp),d0
or should the extl instruction be left out?  muls has already
generated a long result.  Both the Sun and GNU compilers
do not use the extl, but I have seen other compilers that
would.

-- 
Paul Guthrie
chinet!nsacray!paul