Add AArch64 SVE to NEWS and GDB manual

gdb/
	* NEWS: Add SVE to 8.2 section.

gdb/doc/
	* doc/gdb.texinfo (AArch64 SVE): New subsubsection.

gdb/ChangeLog

@@ -1,3 +1,7 @@
+2018-08-21  Alan Hayward  <alan.hayward@arm.com>
+
+	* NEWS: Add SVE to 8.2 section.
+
 2018-08-16  Tom Tromey  <tom@tromey.com>
 
 	* top.c (read_command_file): Update.

gdb/NEWS

@@ -34,6 +34,9 @@
 * C expressions can now use _Alignof, and C++ expressions can now use
   alignof.
 
+* Support for SVE on AArch64 Linux.  Note that GDB does not detect changes to
+  the vector length while the process is running.
+
 * New commands
 
 set debug fbsd-nat

gdb/doc/ChangeLog

@@ -1,3 +1,7 @@
+2018-08-21  Alan Hayward  <alan.hayward@arm.com>
+
+	* gdb.texinfo (AArch64 SVE): New subsubsection.
+
 2018-07-02  Maciej W. Rozycki  <macro@mips.com>
 
 	PR tdep/8282

gdb/doc/gdb.texinfo

@@ -23190,6 +23190,22 @@ Show whether AArch64 debugging messages are displayed.
 
 @end table
 
+@subsubsection AArch64 SVE.
+@cindex AArch64 SVE.
+
+When @value{GDBN} is debugging the AArch64 architecture, if the Scalable Vector
+Extension (SVE) is present, then @value{GDBN} will provide the vector registers
+@code{$z0} through @code{$z31}, vector predicate registers @code{$p0} through
+@code{$p15}, and the @code{$ffr} register.  In addition, the pseudo register
+@code{$vg} will be provided.  This is the vector granule for the current thread
+and represents the number of 64-bit chunks in an SVE @code{z} register.
+
+If the vector length changes, then the @code{$vg} register will be updated,
+but the lengths of the @code{z} and @code{p} registers will not change.  This
+is a known limitation of @value{GDBN} and does not affect the execution of the
+target process.
+
+
 @node i386
 @subsection x86 Architecture-specific Issues