ARM: Make armv7 memcpy implementations SFI-friendly

ports/ChangeLog.arm

@@ -1,5 +1,13 @@
 2013-06-18  Roland McGrath  <roland@hack.frob.com>
 
+	* sysdeps/arm/arm-features.h (ARM_BX_NINSNS): New macro.
+	* sysdeps/arm/armv7/multiarch/memcpy_impl.S: Macroize the
+	computed-jump dispatch sections.  Use sfi_breg throughout.
+	[ARM_ALWAYS_BX]: Define a different version of the dispatch macros
+	that uses bx rather than add-to-pc, and respects ARM_BX_ALIGN_LOG2.
+	[!USE_NEON] (D_l, D_h): Use r10, r11 rather than r8, r9.
+	(tmp2): Use r8 rather than r10.
+
 	* sysdeps/arm/armv7/multiarch/ifunc-impl-list.c (__libc_ifunc_impl_list)
 	[__ARM_NEON__]: Do not refer to HWCAP_ARM_NEON.
 	[!__SOFTFP__]: Do not refer to HWCAP_ARM_VFP.

ports/sysdeps/arm/arm-features.h

@@ -53,6 +53,14 @@
 # define ARM_BX_ALIGN_LOG2	2
 #endif
 
+/* The number of instructions that 'bx' expands to.  A more-specific
+   arm-features.h that defines 'bx' as a macro should define this to the
+   number instructions it expands to.  This is used only in a context
+   where the 'bx' expansion won't cross an ARM_BX_ALIGN_LOG2 boundary.  */
+#ifndef ARM_BX_NINSNS
+# define ARM_BX_NINSNS		1
+#endif
+
 /* An OS-specific arm-features.h file may define ARM_NO_INDEX_REGISTER to
    indicate that the two-register addressing modes must never be used.  */