[PATCH, aarch64] Correctly wire up --with-cpu and --with-arch (PR61714)

[Richard Earnshaw]

I noticed that although configure on aarch64 handles --with-arch and
--with-cpu, they aren't passed on to the compilation -- instead you just
get whatever the internal default is in the compiler back-end.  This
patch fixes that by wiring up the missing logic.

2014-07-04  Richard Earnshaw  <rearnsha@arm.com>

	PR target/61714
	* aarch64.h (OPTION_DEFAULT_SPECS): Define.

Applied to trunk.  It's trivial enough that I'll probably back-port it
to 4.9 as well.

R.
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diff --git a/gcc/config/aarch64/aarch64.h b/gcc/config/aarch64/aarch64.h
index b95365a..080b23f 100644
--- a/gcc/config/aarch64/aarch64.h
+++ b/gcc/config/aarch64/aarch64.h
@@ -879,6 +879,13 @@ extern enum aarch64_code_model aarch64_cmodel;
 #define ENDIAN_LANE_N(mode, n)  \
   (BYTES_BIG_ENDIAN ? GET_MODE_NUNITS (mode) - 1 - n : n)
 
+/* Support for a configure-time default CPU, etc.  We currently support
+   --with-arch and --with-cpu.  Both are ignored if either is specified
+   explicitly on the command line at run time.  */
+#define OPTION_DEFAULT_SPECS				\
+  {"arch", "%{!march=*:%{!mcpu=*:-march=%(VALUE)}}" },	\
+  {"cpu",  "%{!march=*:%{!mcpu=*:-mcpu=%(VALUE)}}" },
+
 #define BIG_LITTLE_SPEC \
    " %{mcpu=*:-mcpu=%:rewrite_mcpu(%{mcpu=*:%*})}"