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From: chris@umcp-cs.UUCP (Chris Torek)
Newsgroups: net.lang.c,net.bugs.4bsd
Subject: Re: C compiler bug
Message-ID: <8174@umcp-cs.UUCP>
Date: Sun, 26-Aug-84 16:13:25 EDT
Article-I.D.: umcp-cs.8174
Posted: Sun Aug 26 16:13:25 1984
Date-Received: Thu, 30-Aug-84 06:22:45 EDT
References: <73@ur-valhalla.UUCP> <8164@umcp-cs.UUCP> <3009@utah-cs.UUCP>
Organization: U of Maryland, Computer Science Dept., College Park, MD
Lines: 24

As long as we have people fixing bugs, how about someone patching up the
pcc/ code that converts RS into LS and negates the shift?  It fixes up
constants but it doesn't remove double negations.  Example:

	foo () { register int i,j,k; k = i >> -j; }

produces (prettified)

	.align	1
	.globl	_foo
_foo:	.word	0xe000
	mnegl	r10,r0
	mnegl	r0,r0
	ashl	r0,r11,r0
	movl	r0,r9
	ret

What's the idea of the double mnegl?  I got disgusted enough with this
(and other similar but tougher-to-optimize) stuff in the output stage of
my Versatec TeX filter that I stuck in asm()s (under #ifdef vax though).
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci (301) 454-7690
UUCP:	{seismo,allegra,brl-bmd}!umcp-cs!chris
CSNet:	chris@umcp-cs		ARPA:	chris@maryland