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Re: [trunk] Addition to subreg section of rtl.text.
- From: Kenneth Zadeck <zadeck at naturalbridge dot com>
- To: Kenneth Zadeck <zadeck at naturalbridge dot com>, law at redhat dot com, dj at redhat dot com, rth at redhat dot com, Ian Lance Taylor <iant at google dot com>, gcc <gcc at gcc dot gnu dot org>, "Bonzini\, Paolo" <bonzini at gnu dot org>, rsandifo at nildram dot co dot uk, Joern Rennecke <joernr at arc dot com>, Richard Kenner <kenner at vlsi1 dot ultra dot nyu dot edu>, Bernd Schmidt <bernds_cb1 at t-online dot de>
- Date: Mon, 24 Mar 2008 09:46:50 -0400
- Subject: Re: [trunk] Addition to subreg section of rtl.text.
- References: <47DA8A3E.7060002@naturalbridge.com> <87iqzpz7vj.fsf@firetop.home> <m3od9hqs00.fsf@google.com> <47DD409C.1080904@naturalbridge.com> <87abkodzjs.fsf@firetop.home> <8763vcdywi.fsf@firetop.home>
Richard Sandiford wrote:
Richard Sandiford <rsandifo@nildram.co.uk> writes:
- A MODE_PARTIAL_INT mode behaves like the corresponding MODE_INT mode.
...except that (as the docs said) an unknown number of bits read as undefined.
Richard
I would add two things to the section. One is to recommend in the text
that subregs of hard regs not be used if possible. The advantages that
these provide are marginal and there is a reasonable chance that they
will be outlawed in the future. The second is to say explicitly that
subregs of subregs are not legal. I know that the df code will ignore
the "middle" subreg.
Kenny