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Subject: Re: [patch][simplify-rtx] Fix 16-bit -> 64-bit multiply and	accumulate
From: Richard Earnshaw <rearnsha@arm.com>
To: Andrew Stubbs <ams@codesourcery.com>
Cc: "Joseph S. Myers" <joseph@codesourcery.com>, Bernd Schmidt <bernds@codesourcery.com>, gcc-patches@gcc.gnu.org, patches@linaro.org
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On Thu, 2011-05-26 at 14:35 +0100, Andrew Stubbs wrote:
> On 25/05/11 14:47, Joseph S. Myers wrote:
> > The shift must be by a positive constant amount, strictly less than the
> > precision (GET_MODE_PRECISION) of the mode (of the value being shifted).
> > If that applies, the relevant number of bits is the precision of the mo=
de
> > minus the number of bits of the shift.  For an extension, just take the
> > number of bits in the inner mode.  Add the two numbers of bits; if the
> > result does not exceed the number of bits in the mode (of the operands =
and
> > the multiplication) then the multiplication won't overflow.
>=20
> I believe the attached should implement what you describe.
>=20
> Is the patch OK now?
>=20
> Andrew

OK.

R.