toolchain/gcc (linaro): fix extension elimination optimization

This applies Richard Sandiford's patch for Linaro GCC as an alternative to disabling the Linaro-specific extension elimination optimization altogether.

Original patch: https://bugs.launchpad.net/gcc-linaro/+bug/728315
Signed-off-by: Mark Mentovai <mark@moxienet.com>

git-svn-id: svn://svn.openwrt.org/openwrt/trunk@25871 3c298f89-4303-0410-b956-a3cf2f4a3e73

toolchain/gcc/patches/linaro/860-disable_extension_elimination.patch

@@ -1,11 +0,0 @@
---- a/gcc/opts.c
-+++ b/gcc/opts.c
-@@ -906,7 +906,7 @@ decode_options (unsigned int argc, const
-   flag_tree_if_to_switch_conversion = opt2;
-   flag_ipa_cp = opt2;
-   flag_ipa_sra = opt2;
--  flag_ee = opt2;
-+  flag_ee = 0;
- 
-   /* Track fields in field-sensitive alias analysis.  */
-   set_param_value ("max-fields-for-field-sensitive",

toolchain/gcc/patches/linaro/860-fix_extension_elimination.patch

@@ -0,0 +1,18 @@
+https://bugs.launchpad.net/gcc-linaro/+bug/728315
+https://lists.openwrt.org/pipermail/openwrt-devel/2011-March/009847.html
+
+--- a/gcc/ee.c
++++ b/gcc/ee.c
+@@ -209,7 +209,11 @@
+
+       *regno = REGNO (reg);
+
+-      if (paradoxical_subreg_p (use))
++      /* Non-paradoxical SUBREGs of promoted vars guarantee that the
++	 upper (elided) bits of the inner register have a particular value.
++	 For our purposes, such SUBREGs act as a full reference to the
++	 inner register.  */
++      if (paradoxical_subreg_p (use) || SUBREG_PROMOTED_VAR_P (use))
+         *size = GET_MODE_BITSIZE (GET_MODE (reg));
+       else
+         *size = subreg_lsb (use) + GET_MODE_BITSIZE (GET_MODE (use));