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Re: RFC: Simplify rules for ctz/clz patterns and RTL

From: Zack Weinberg <zack at codesourcery dot com>
To: Andrew Pinski <pinskia at gmail dot com>
Cc: Segher Boessenkool <segher at kernel dot crashing dot org>, gcc at gcc dot gnu dot org
Date: Wed, 15 Aug 2007 11:55:57 -0700
Subject: Re: RFC: Simplify rules for ctz/clz patterns and RTL
References: <46BD5B17.9080009@codesourcery.com> <62defd1ecb56eda092535c7147d5d3c6@kernel.crashing.org> <46C34786.3@codesourcery.com> <de8d50360708151144o15f8ea21obd1d1bab21ffc581@mail.gmail.com>

Andrew Pinski wrote:

On 8/15/07, Zack Weinberg <zack@codesourcery.com> wrote:
Is popcount really slow on PowerPC? (Compared to clz?)
popcount is really popcount in bytes and then you do a multiple to get
the real popcount.  This is why it is slower than count leading zeros.
 Also popcount does not exist in most powerpc's while count leading
zeros exist in all.

Makes sense. I don't suppose I could persuade you to teach rs6000 RTX_COSTS about clz and popcount...?

zw

Follow-Ups:
- Re: RFC: Simplify rules for ctz/clz patterns and RTL
  - From: David Edelsohn
- Re: RFC: Simplify rules for ctz/clz patterns and RTL
  - From: David Edelsohn

References:
- RFC: Simplify rules for ctz/clz patterns and RTL
  - From: Zack Weinberg
- Re: RFC: Simplify rules for ctz/clz patterns and RTL
  - From: Segher Boessenkool
- Re: RFC: Simplify rules for ctz/clz patterns and RTL
  - From: Zack Weinberg
- Re: RFC: Simplify rules for ctz/clz patterns and RTL
  - From: Andrew Pinski

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