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Re: birthpoints in rtl.

From: Paolo Bonzini <bonzini at gnu dot org>
To: Diego Novillo <dnovillo at google dot com>
Cc: Steven Bosscher <stevenb dot gcc at gmail dot com>, Kenneth Zadeck <zadeck at naturalbridge dot com>, gcc <gcc at gcc dot gnu dot org>, "Park, Seongbae" <seongbae dot park at gmail dot com>, Ian Lance Taylor <iant at google dot com>, Richard Sandiford <rsandifo at nildram dot co dot uk>
Date: Sat, 01 Mar 2008 14:50:35 +0100
Subject: Re: birthpoints in rtl.
References: <47C5EF2A.5020401@naturalbridge.com> <47C6B132.3090903@naturalbridge.com> <47C88C6B.8030809@google.com> <571f6b510802291604t6ba0d302uc1a6bda69a7f807@mail.gmail.com> <47C89EC3.7030109@google.com>

Diego Novillo wrote:

On 2/29/08 7:04 PM, Steven Bosscher wrote:
I am not sure what would happen if GCC would start using FUD chains.
Is it like in SSA that every register is assigned only once?
But this would only affect the UD chains built by the DF code.

Yes, that's what I meant by "no subscripts" (see also my other message re. birthpoints). Instead of subscripting variables you have multiple defs for each variable. End each def is obviously assigned only once, and each use in the IL stream except for phis has only one reaching def.

You do not necessarily need to think of subscripts, though they are a clean notation for singleton UD chains.

Paolo

Follow-Ups:
- Re: birthpoints in rtl.
  - From: Diego Novillo

References:
- Re: birthpoints in rtl.
  - From: Steven Bosscher
- Re: birthpoints in rtl.
  - From: Diego Novillo

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