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From: johnt@microsoft.UUCP
Newsgroups: comp.arch
Subject: Re: Available no. of registers
Message-ID: <170@microsoft.UUCP>
Date: Thu, 22-Jan-87 12:28:54 EST
Article-I.D.: microsof.170
Posted: Thu Jan 22 12:28:54 1987
Date-Received: Sat, 24-Jan-87 09:46:17 EST
References: <3810002@nucsrl.UUCP> <926@mips.UUCP> <759@vaxb.calgary.UUCP>
Organization: Microsoft, Inc., Redmond, Washington
Lines: 30
Summary: inner scopes and registers

> Shouldn't a compiler smart enough to allocate variables to registers be
> smart enough to see that a local variable is never the operand of the
> & (address-of) operator, and thus cannot be referenced by a pointer?

God forbid, but there is probably some C program out there that relies
on being able to:
	int a,b, *ptr;

	ptr = &a;
	ptr++;
	/* ptr now points to b */
No flames please, if there is such a program out there, >I< didn't write it.

> . . . Unfortunately if you use inner scopes this isn't always possible.
> E.g.
> 
>    proc()
>    { register int blat, blog, blit;
>      ...
>      { register int glip, glop, glurp;
>        ...
>      }
>    }

I once used a 68000 compiler that would indeed ignore 'register' for inner
scope variables.  I ended up moving all the variable declarations to the head
of the procedure.
-----
John Tupper
...!decvax!microsoft!johnt