simplify-rtx.c (simplify_binary_operation_1): Handle (xor (and A B) C) case when…

simplify-rtx.c (simplify_binary_operation_1): Handle (xor (and A B) C) case when B and C are both constants.

2011-03-21  Chung-Lin Tang  <cltang@codesourcery.com>

	* simplify-rtx.c (simplify_binary_operation_1): Handle
	(xor (and A B) C) case when B and C are both constants.

	testsuite/
	* gcc.target/arm/xor-and.c: New.

From-SVN: r171208

gcc/ChangeLog

+2011-03-21  Chung-Lin Tang  <cltang@codesourcery.com>
+
+	* simplify-rtx.c (simplify_binary_operation_1): Handle
+	(xor (and A B) C) case when B and C are both constants.
+
 2011-03-21  Mingjie Xing  <mingjie.xing@gmail.com>
 
 	* tree-dfa.c (add_referenced_var): Fix typo in comment.

gcc/simplify-rtx.c

@@ -2480,6 +2480,46 @@ simplify_binary_operation_1 (enum rtx_code code, enum machine_mode mode,
 							XEXP (op0, 1), mode),
 				    op1);
 
+      /* Given (xor (and A B) C), using P^Q == (~P&Q) | (~Q&P),
+	 we can transform like this:
+            (A&B)^C == ~(A&B)&C | ~C&(A&B)
+                    == (~A|~B)&C | ~C&(A&B)    * DeMorgan's Law
+                    == ~A&C | ~B&C | A&(~C&B)  * Distribute and re-order
+	 Attempt a few simplifications when B and C are both constants.  */
+      if (GET_CODE (op0) == AND
+	  && CONST_INT_P (op1)
+	  && CONST_INT_P (XEXP (op0, 1)))
+	{
+	  rtx a = XEXP (op0, 0);
+	  rtx b = XEXP (op0, 1);
+	  rtx c = op1;
+	  HOST_WIDE_INT bval = INTVAL (b);
+	  HOST_WIDE_INT cval = INTVAL (c);
+
+	  rtx na_c
+	    = simplify_binary_operation (AND, mode,
+					 simplify_gen_unary (NOT, mode, a, mode),
+					 c);
+	  if ((~cval & bval) == 0)
+	    {
+	      /* Try to simplify ~A&C | ~B&C.  */
+	      if (na_c != NULL_RTX)
+		return simplify_gen_binary (IOR, mode, na_c,
+					    GEN_INT (~bval & cval));
+	    }
+	  else
+	    {
+	      /* If ~A&C is zero, simplify A&(~C&B) | ~B&C.  */
+	      if (na_c == const0_rtx)
+		{
+		  rtx a_nc_b = simplify_gen_binary (AND, mode, a,
+						    GEN_INT (~cval & bval));
+		  return simplify_gen_binary (IOR, mode, a_nc_b,
+					      GEN_INT (~bval & cval));
+		}
+	    }
+	}
+
       /* (xor (comparison foo bar) (const_int 1)) can become the reversed
 	 comparison if STORE_FLAG_VALUE is 1.  */
       if (STORE_FLAG_VALUE == 1

gcc/testsuite/ChangeLog

+2011-03-21  Chung-Lin Tang  <cltang@codesourcery.com>
+
+	* gcc.target/arm/xor-and.c: New.
+
 2010-03-21  Thomas Koenig  <tkoenig@gcc.gnu.org>
 
 	PR fortran/22572

gcc/testsuite/gcc.target/arm/xor-and.c

+/* { dg-do compile } */
+/* { dg-options "-O -march=armv6" } */
+
+unsigned short foo (unsigned short x)
+{
+  x ^= 0x4002;
+  x >>= 1;
+  x |= 0x8000;
+  return x;
+}
+
+/* { dg-final { scan-assembler "orr" } } */
+/* { dg-final { scan-assembler-not "mvn" } } */
+/* { dg-final { scan-assembler-not "uxth" } } */