From: Adam Nemet <anemet@caviumnetworks.com>
To: Ian Lance Taylor <iant@google.com>
Cc: gcc@gcc.gnu.org, law@redhat.com
Subject: Re: Rationale for an old TRUNCATE patch
Date: Wed, 17 Jun 2009 15:26:00 -0000 [thread overview]
Message-ID: <19001.2856.220185.280288@ropi.home> (raw)
In-Reply-To: <m3ocsnuef1.fsf@google.com>
Ian Lance Taylor writes:
> I'm not entirely sure, but I don't think Jim said the opposite. He said
> that the way truncate works is machine dependent. I said that the
> output of truncate is machine independent. Since truncate is only
> defined for fixed-point modes, I think both statements are true.
OK but in that way every operation is machine dependent not just truncate.
BTW, why is being fixed-point relevant here?
From that little excerpt I just gathered that maybe my misunderstanding of
treating truncate as a blackbox was not completely without precedence. But
anyway I think I understand now. JTBS, can you agree with other statement in
my email?:
> And IIUC this don't-care nature of the other bits that allows backends to
> define the upper bits. For example to have sign-bit copies there in registers
> to enforce the MIPS64 SI mode representation. And treating the don't care
> bits outside SI mode in this way is true for any other SI-mode operations
> performed on registers not just truncate, right? Hmm, nice.
Thanks for all the explanations.
Adam
next prev parent reply other threads:[~2009-06-17 15:26 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-16 7:12 Adam Nemet
2009-06-16 14:35 ` Ian Lance Taylor
2009-06-16 22:45 ` Adam Nemet
2009-06-17 0:28 ` Ian Lance Taylor
2009-06-17 6:42 ` Adam Nemet
2009-06-17 14:24 ` Ian Lance Taylor
2009-06-17 15:26 ` Adam Nemet [this message]
2009-06-17 15:54 ` Ian Lance Taylor
2009-06-17 2:12 ` Jeff Law
2009-06-17 6:17 ` Adam Nemet
2009-06-17 14:52 ` Jeff Law
2009-06-17 2:10 ` Jeff Law
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