[combine][v2] Canonicalise (r + r) to (r << 1) to aid recognition

	PR rtl-optimization/68651
	* combine.c (combine_simplify_rtx): Canonicalize x + x into
	x << 1.

	* gcc.target/aarch64/pr68651_1.c: New test.

From-SVN: r232077

gcc/ChangeLog

+2016-01-05  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/68651
+	* combine.c (combine_simplify_rtx): Canonicalize x + x into
+	x << 1.
+
 2016-01-05  Nathan Sidwell  <nathan@acm.org>
 
 	* alias.c (compare_base_decls): Use symtab_node::get.

gcc/combine.c

@@ -5895,6 +5895,13 @@ combine_simplify_rtx (rtx x, machine_mode op0_mode, int in_dest,
 			  || XEXP (temp, 1) != XEXP (x, 0)))))
 	    return temp;
 	}
+
+      /* Canonicalize x + x into x << 1.  */
+      if (GET_MODE_CLASS (mode) == MODE_INT
+	  && rtx_equal_p (XEXP (x, 0), XEXP (x, 1))
+	  && !side_effects_p (XEXP (x, 0)))
+	return simplify_gen_binary (ASHIFT, mode, XEXP (x, 0), const1_rtx);
+
       break;
 
     case MINUS:

gcc/testsuite/ChangeLog

+2016-01-05  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	PR rtl-optimization/68651
+	* gcc.target/aarch64/pr68651_1.c: New test.
+
 2016-01-05  David Malcolm  <dmalcolm@redhat.com>
 
 	PR c/69122

gcc/testsuite/gcc.target/aarch64/pr68651_1.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -mcpu=cortex-a53" } */
+
+int
+foo (int x)
+{
+  return (x * 2) & 65535;
+}
+/* { dg-final { scan-assembler "ubfiz\tw\[0-9\]*, w\[0-9\]*.*\n" } } */
+
+int
+bar (int x, int y)
+{
+  return (x * 2) | y;
+}
+/* { dg-final { scan-assembler "orr\tw\[0-9\]*, w\[0-9\]*, w\[0-9\]*, lsl 1.*\n" } } */