Re: copy propagation?

Anthony PIRON <>
15 Feb 2001 00:42:07 -0500

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Related articles
copy propagation? ppanda@Rational.Com (Partha Sarathi Panda) (2001-02-12)
Re: copy propagation? (Anthony PIRON) (2001-02-15)
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From: Anthony PIRON <>
Newsgroups: comp.compilers
Date: 15 Feb 2001 00:42:07 -0500
Organization: VUB/ULB Computing Centre
References: 01-02-055
Keywords: optimize
Posted-Date: 15 Feb 2001 00:42:07 EST


  It's seem simple may be I'm wrong.

if you have got something like:


you can replace every occurrence of a0 by a1.
a0=a1 // now deadcode (if no side effects on the a0 variable)
suppress this instruction

if you obtain for some phi node all the same right-hand parameters do
the same transformation for this phi node
a0=a1 ...
        \ /
            = a2
becomes to
a0=a1 ... // now dead code (a0-a1)
        \ /
        a2=phi(a1,a1) // now dead code
            = a1

Theses things can be done during sparse representation building. And the
dead code is never introduced (immediately removed).

Pariah Sarathi Panda wrote:

> How can copy propagation be done using sparse data-flow information
> and without doing register renaming?

What's the signification of "without register renaming". There is
always renaming in copy propagation.

Anthony PIRON - Researcher
Universite Libre de Bruxelles, Department of Computer Science
CP 212 - Boulevard du Triomphe, B-1050 Bruxelles, Belgium
Tel. +32 2 650 50 55, Fax +32 2 650 56 09, GSM +32 478 530 022
Email: Web:

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