[Boost-bugs] [Boost C++ Libraries] #8574: Optimization for 64 bit loads and stores for 32 bit x86 on gcc

Subject: [Boost-bugs] [Boost C++ Libraries] #8574: Optimization for 64 bit loads and stores for 32 bit x86 on gcc
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2013-05-14 20:28:59

#8574: Optimization for 64 bit loads and stores for 32 bit x86 on gcc
-------------------------------------+--------------------------------------
 Reporter:  andysem                  |       Owner:  timblechmann
     Type:  Patches                  |      Status:  new         
Milestone:  To Be Determined         |   Component:  atomic      
  Version:  Boost Development Trunk  |    Severity:  Problem     
 Keywords:                           |  
-------------------------------------+--------------------------------------
 The attached patch contains some fixes and optimizations for 32 bit x86
 atomics support for gcc and its pretenders. In particular, the patch
 contains:

 1. Fix for BOOST_ATOMIC_LLONG_LOCK_FREE macro value on 32 bit x86. The
 macro should have value 2 when cmpxchg8b instruction is enabled in compile
 time and 0 otherwise (as long as Boost.Atomic doesn't perform run time
 detection).
 2. Fixed compile time cmpxchg8b presence check. The previous check only
 worked on compilers with __sync* intrinsics support or on i686 class CPUs
 (but not later or i586).
 3. Optimized 64 bit loads and stores in 32 bit x86. When the target/source
 memory is 8-byte aligned (which is the most common case) it is possible to
 avoid expensive "lock cmpxchg8b" and use regular loads and stores instead.
 4. Added a few missing noexcept specifications.

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/8574>
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