From: Richard Henderson <rth@redhat.com>
To: Roger Sayle <roger@eyesopen.com>
Cc: gcc@gcc.gnu.org, gcc-patches@gcc.gnu.org,
Joern Rennecke <joern.rennecke@superh.com>
Subject: Re: Floating point registers vs. LOAD_EXTEND_OP on alpha
Date: Sun, 18 Jan 2004 19:01:00 -0000 [thread overview]
Message-ID: <20040118190110.GA14030@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0401181003080.27690-100000@www.eyesopen.com>
On Sun, Jan 18, 2004 at 10:18:59AM -0700, Roger Sayle wrote:
> 594a595
> > cvtlq $f2,$f2
> 716a718
> > cvtlq $f3,$f3
> 846a849
> > cvtlq $f4,$f4
>
>
> The patch has eliminated the sign extensions of an integer value held
> in the alpha's floating point registers.
I hope you mean *added*.
> Clearly there's some poor interaction between LOAD_EXTEND_OP and
> loading integer values into FP registers.
Yes. LOAD_EXTEND_OP is not true for the FP registers, only
the integer registers. This is a problem...
> I'm guesing that in the sequence:
>
> lds $f2,40($10)
> cvtlq $f2,$f2
> sts $f2,40($9)
>
> the "cvtlq" is actually doing something useful ...
No, the cvtlq insn there is actually corrupting data.
> Hopefully, this analysis is enough for an alpha maintainer to determine
> whether Joern needs an additional check in his post-reload patch or if
> the alpha backend's LOAD_EXTEND_OP should claim to be extending in these
> modes.
What we need to do is run some benchmarks and decide if LOAD_EXTEND_OP
should be removed, or (much more likely) we remove (or obfuscate) the
bits that claims that we can load SImode values into FP registers.
r~
next prev parent reply other threads:[~2004-01-18 19:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-01-18 18:05 Roger Sayle
2004-01-18 19:01 ` Richard Henderson [this message]
2004-01-18 22:29 ` Richard Henderson
2004-01-19 20:33 ` Joern Rennecke
2004-01-19 20:41 ` Richard Henderson
2004-01-20 9:30 ` Richard Sandiford
2004-01-20 17:17 ` Richard Henderson
2004-01-20 19:05 ` Joern Rennecke
2004-01-20 19:21 ` Joern Rennecke
2004-01-26 19:30 ` Eric Botcazou
2004-01-26 19:46 ` Joern Rennecke
2004-01-26 20:06 ` Gerald Pfeifer
2004-01-26 20:53 ` Joern Rennecke
2004-01-26 21:16 ` Eric Botcazou
2004-01-26 21:18 ` Gabriel Dos Reis
2004-01-26 20:38 ` Eric Botcazou
2004-01-22 9:49 ` Richard Sandiford
2004-01-22 19:32 ` Richard Henderson
2004-01-19 21:25 ` Joern Rennecke
2004-01-19 21:38 ` Richard Henderson
2004-01-18 20:42 Richard Kenner
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