Index: combine.c
===================================================================
--- combine.c	(revision 191681)
+++ combine.c	(working copy)
@@ -5314,6 +5314,26 @@ combine_simplify_rtx (rtx x, enum machine_mode op0
       break;
     case RTX_COMM_ARITH:
     case RTX_BIN_ARITH:
+      if ((code == PLUS || code == MINUS)
+	  && GET_MODE_CLASS (mode) == MODE_INT
+	  && HWI_COMPUTABLE_MODE_P (mode))
+	{
+	  /* Adjust operands in the form of (subreg:M (op:N A C) 0)
+	     to (op:M (subreg:N (A 0)) C).  This transformation 
+	     generates canonical (plus:M (plus:M (subreg:N (A 0) C1) C2))
+	     RTXes that can be recognized and further optimized by
+	     simplify_plus_minus.  */
+	  if (GET_CODE (XEXP (x, 0)) == SUBREG
+	      && plus_minus_operand_p (SUBREG_REG (XEXP (x, 0))))
+	    SUBST (XEXP (x, 0),
+		   force_to_mode (XEXP (x, 0), mode,
+				  ~(unsigned HOST_WIDE_INT) 0, 0));
+	  if (GET_CODE (XEXP (x, 1)) == SUBREG
+	      && plus_minus_operand_p (SUBREG_REG (XEXP (x, 1))))
+	    SUBST (XEXP (x, 1),
+		   force_to_mode (XEXP (x, 1), mode,
+				  ~(unsigned HOST_WIDE_INT) 0, 0));
+	}
       temp = simplify_binary_operation (code, mode, XEXP (x, 0), XEXP (x, 1));
       break;
     case RTX_BITFIELD_OPS:
Index: rtl.h
===================================================================
--- rtl.h	(revision 191681)
+++ rtl.h	(working copy)
@@ -1895,6 +1895,7 @@ extern bool val_signbit_known_set_p (enum machine_
 				     unsigned HOST_WIDE_INT);
 extern bool val_signbit_known_clear_p (enum machine_mode,
 				       unsigned HOST_WIDE_INT);
+extern bool plus_minus_operand_p (const_rtx);
 
 /* In reginfo.c  */
 extern enum machine_mode choose_hard_reg_mode (unsigned int, unsigned int,
Index: simplify-rtx.c
===================================================================
--- simplify-rtx.c	(revision 191681)
+++ simplify-rtx.c	(working copy)
@@ -48,7 +48,6 @@ along with GCC; see the file COPYING3.  If not see
  ((((HOST_WIDE_INT) low) < 0) ? ((HOST_WIDE_INT) -1) : ((HOST_WIDE_INT) 0))
 
 static rtx neg_const_int (enum machine_mode, const_rtx);
-static bool plus_minus_operand_p (const_rtx);
 static bool simplify_plus_minus_op_data_cmp (rtx, rtx);
 static rtx simplify_plus_minus (enum rtx_code, enum machine_mode, rtx, rtx);
 static rtx simplify_immed_subreg (enum machine_mode, rtx, enum machine_mode,
@@ -4186,7 +4185,7 @@ simplify_plus_minus (enum rtx_code code, enum mach
 }
 
 /* Check whether an operand is suitable for calling simplify_plus_minus.  */
-static bool
+bool
 plus_minus_operand_p (const_rtx x)
 {
   return GET_CODE (x) == PLUS