* doc/invoke.texi (PowerPC Options): Document 'native' cpu type.

From-SVN: r257063

gcc/ChangeLog

+2018-01-25  David Edelsohn  <dje.gcc@gmail.com>
+
+	* doc/invoke.texi (PowerPC Options): Document 'native' cpu type.
+
 2018-01-25  Jan Hubicka  <hubicka@ucw.cz>
 
 	PR middle-end/83055

gcc/doc/invoke.texi

@@ -22333,7 +22333,7 @@ Supported values for @var{cpu_type} are @samp{401}, @samp{403},
 @samp{titan}, @samp{power3}, @samp{power4}, @samp{power5}, @samp{power5+},
 @samp{power6}, @samp{power6x}, @samp{power7}, @samp{power8},
 @samp{power9}, @samp{powerpc}, @samp{powerpc64}, @samp{powerpc64le},
-and @samp{rs64}.
+@samp{rs64}, and @samp{native}.
 
 @option{-mcpu=powerpc}, @option{-mcpu=powerpc64}, and
 @option{-mcpu=powerpc64le} specify pure 32-bit PowerPC (either
@@ -22341,6 +22341,12 @@ endian), 64-bit big endian PowerPC and 64-bit little endian PowerPC
 architecture machine types, with an appropriate, generic processor
 model assumed for scheduling purposes.
 
+Specifying @samp{native} as cpu type detects and selects the
+architecture option that corresponds to the host processor of the
+system performing the compilation.
+@option{-march=native} has no effect if GCC does not recognize the
+processor.
+
 The other options specify a specific processor.  Code generated under
 those options runs best on that processor, and may not run at all on
 others.