Re: Enhancements to strength-reduction code.

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Article #2471

#2471

From: Michael Meissner
Date: Mon, 27 Mar 1989 16:19

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I just tried this out with GCC 1.34, and found that it exposes a
latent bug in loop optimization caused by 1.34.  I tried to recompile
the 88k compiler with it, and when I got to global-alloc.c, it aborted
with an insn not found.  The insn involved looked like:

	(set cc0 (minus (match_operand:SI 0 "register_operand" "r")
			(const_int 0)))

This was how you set the condition code under 1.33 and before.  However,
under 1.34 a new RTL operator was added 'compare', so the RTX should
look like:

	(set cc0 (compare (match_operand:SI 0 "register_operand" "r")
			  (const_int 0)))

I will look at this on my own, but this quick description might set off
bells for somebody more familar with that section of code.

Michael Meissner, Data General.
Uucp:		...!mcnc!rti!xyzzy!meissner		If compiles were much
Internet:	meissner@dg-rtp.DG.COM			faster, when would we
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From: meissner@bert.dg.com (Michael Meissner)
Newsgroups: gnu.gcc.bug
Subject: Re: Enhancements to strength-reduction code.
Message-ID: <4561@xyzzy.UUCP>
Date: 27 Mar 89 16:19:17 GMT
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