[PATCH, WIP] NEON quadword vectors in big-endian mode (#10061, #7306)

[Joseph S. Myers]

On Tue, 30 Nov 2010, Julian Brown wrote:

>     * defaults.h (VECTOR_ELEMENTS_BIG_ENDIAN): Define.

Apart from the point that new target macros should be hooks, the *very 
first* thing to do with any new macro or hook is to write the .texi 
documentation, which appears to be missing from this patch.  This is best 
done before making any consequent code changes.  That documentation needs 
to make clear:

* What the effects are on the semantics of GNU C code (that uses generic 
vector extensions - which in 4.6 include subscripting), if any.

* What the effects are on the semantics of GENERIC and GIMPLE using vector 
types, if any.  If the semantics of memory references to such types are 
affected, or the semantics of any other existing GENERIC or GIMPLE 
operation (most likely any operations that may exist involving lane 
numbers) then you need to make clear how, and ensure that any 
documentation / comments for that operation are updated as well; the patch 
submission needs to make clear how you have audited all existing code for 
correctness given such a change - any code mentioning a GENERIC or GIMPLE 
code may do transformations assuming particular semantics.

* Likewise, for all machine-independent RTL operations.

* For UNSPECs the documentation issue doesn't arise, but the audit is 
still relevant.

-- 
Joseph S. Myers
joseph at codesourcery.com