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Re: [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bit targets

To: Richard Sandiford <rsandifo@redhat.com>
Subject: Re: [patch] MIPS/gcc: Revert removal of DImode shifts for 32-bit targets
From: Richard Henderson <rth@redhat.com>
Date: Tue, 10 Aug 2004 16:20:20 -0700
Cc: "Maciej W. Rozycki" <macro@linux-mips.org>, Nigel Stephens <nigel@mips.com>, gcc-patches@gcc.gnu.org, linux-mips@linux-mips.org
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On Tue, Aug 10, 2004 at 06:30:28AM +0100, Richard Sandiford wrote:
> The whole thing's in a sequence that gets discarded if
> expand_doubleword_shift returns false.  Isn't that enough?

Missed that, sorry.

Patch seems ok then.  We'd have to add a new macro/target flag
to handle non-truncating shifts -- we've got cases:

  (1) Large shift shifts out all bits (ARM)
  (2) Large shifts trap (VAX)
  (3) Shift count truncated to 31, always, which means QI/HI
      shifts are yield undefined results with large shifts.  (i386)


r~

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