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Re: 32 x 32 -> 64 bit widening multiply on x86_64

From: Mark Dickinson <dickinsm at gmail dot com>
To: gcc-help at gcc dot gnu dot org
Date: Tue, 11 Nov 2008 15:41:54 +0000 (UTC)
Subject: Re: 32 x 32 -> 64 bit widening multiply on x86_64
References: <5c6f2a5d0811110208u5161fa10s2e9bea92f117e8b3@mail.gmail.com> <m363mu471y.fsf@google.com>

Ian Lance Taylor <iant <at> google.com> writes:

> In order to use the 64-bit value, gcc would have
> to generate code to reassemble the two registers into one.  On balance
> it's normally preferable to simply use the 64 x 64 -> 64 multiply.

Ah.  That makes sense.  Thank you.

Mark

References:
- 32 x 32 -> 64 bit widening multiply on x86_64
  - From: Mark Dickinson
- Re: 32 x 32 -> 64 bit widening multiply on x86_64
  - From: Ian Lance Taylor

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