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Re: recent troubles with float vectors & bitwise ops

From: Paolo Bonzini <bonzini at gnu dot org>
To: Ross Ridge <rridge at csclub dot uwaterloo dot ca>
Cc: gcc at gcc dot gnu dot org
Date: Thu, 23 Aug 2007 08:12:56 +0200
Subject: Re: recent troubles with float vectors & bitwise ops
References: <20070822180847.01B8674BB7@caffeine.csclub.uwaterloo.ca>

The IA-32 instruction set does distignuish between integer and
floating point bitiwse operations.  In addition to the single-precision
floating-point bitwise instructions that tbp mentioned (ORPS, ANDPS,
ANDNPS and XORPS) there are both distinct double-precision floating-point
bitwise instructions (ORPD, ANDPD, ANDNPD and XORPD) and integer bitwise
instructions (POR, PAND, PANDN and PXOR).  While these operations all do
the same thing, they can differ in performance depending on the context.

Oops, I only remembered PS vs. PD (I remembered POR as MMX instructions only). I believe that optimizing this should be a task for the x86 machine dependent reorg.

Paolo

References:
- Re: recent troubles with float vectors & bitwise ops
  - From: Ross Ridge

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