[PATCH, rs6000] Document location of ELF V2 ABI specification

[Bill Schmidt <wschmidt@linux.vnet.ibm.com>]

Hi,

There is finally a permanent link to the OpenPOWER ELF V2 ABI Specification
document.  This patch adds a paragraph to the PowerPC Built-Ins section of
the GCC documentation to describe its value and provide a link to it.

I've generated and verified the PDF, and it looks ok.  I am very open to
changes in wording.  Is this ok for trunk?

Thanks,
Bill


2017-03-29  Bill Schmidt  <wschmidt@linux.vnet.ibm.com>

	* doc/extend.texi (6.60.22 PowerPC AltiVec Built-in Functions):
	Add reference to the OpenPOWER 64-Bit ELF V2 ABI Specification.


Index: gcc/doc/extend.texi
===================================================================
--- gcc/doc/extend.texi	(revision 246566)
+++ gcc/doc/extend.texi	(working copy)
@@ -15539,6 +15539,15 @@ Internally, GCC uses built-in functions to achieve
 the aforementioned header file, but they are not supported and are
 subject to change without notice.
 
+GCC complies with the OpenPOWER 64-Bit ELF V2 ABI Specification,
+which may be found at
+@uref{http://openpowerfoundation.org/wp-content/uploads/resources/leabi-prd/content/index.html}.
+Appendix A of this document lists the vector API interfaces that must be
+provided by compliant compilers.  Programmers should preferentially use
+the interfaces described therein.  However, historically GCC has provided
+additional interfaces for access to vector instructions.  These are
+described briefly below.
+
 The following interfaces are supported for the generic and specific
 AltiVec operations and the AltiVec predicates.  In cases where there
 is a direct mapping between generic and specific operations, only the