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Re: sizeof(long double) vs. std::numeric_limits and x86-64 vs x86

From: Michael Veksler <mveksler at tx dot technion dot ac dot il>
To: Ian Lance Taylor <iant at google dot com>
Cc: Michael Veksler <mveksler at techunix dot technion dot ac dot il>, gcc-help at gcc dot gnu dot org
Date: Tue, 27 Sep 2011 14:29:17 +0300
Subject: Re: sizeof(long double) vs. std::numeric_limits and x86-64 vs x86
References: <4E80F88F.2050608@tx.technion.ac.il> <mcrmxdqgbvq.fsf@coign.corp.google.com>

On 09/27/2011 01:46 AM, Ian Lance Taylor wrote:

Alas, no. On x86_64 long double is an 80-bit floating point number,
just as on 32-bit x86.  The size is 16 bytes because the x86_64 prefers
to align large values to 8-byte boundaries.

gcc works this way because the 80-bit floating point format is supported
directly in hardware, unlike the 128-bit format.

I suspected that this is the case, but hoped for the better.

Thanks

--

Michael

References:
- sizeof(long double) vs. std::numeric_limits and x86-64 vs x86
  - From: Michael Veksler
- Re: sizeof(long double) vs. std::numeric_limits and x86-64 vs x86
  - From: Ian Lance Taylor

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