pr64818-combine-user-specified-register-4.9-2015q1.patch

--- gcc-arm-none-eabi-4_9-2015q1-20150306/src/gcc/gcc/combine.c.old 2015-01-13 18:14:51.000000000 +0100
+++ gcc-arm-none-eabi-4_9-2015q1-20150306/src/gcc/gcc/combine.c 2015-03-25 11:29:04.869039426 +0100
@@ -1835,6 +1835,14 @@
   set = expand_field_assignment (set);
   src = SET_SRC (set), dest = SET_DEST (set);

+  /* Use REG_USERVAR_P and HARD_REGISTER_P to check whether DEST is a user
+     specified register, and do not eliminate such register if it is in an
+     asm input.  Otherwise if allow such elimination, we may break the
+     register asm usage defined in GCC manual.  */
+  if (REG_P (dest) && REG_USERVAR_P (dest) && HARD_REGISTER_P (dest)
+      && extract_asm_operands (PATTERN (i3)))
+    return 0;
+
   /* Don't eliminate a store in the stack pointer.  */
   if (dest == stack_pointer_rtx
       /* Don't combine with an insn that sets a register to itself if it has