[simplify-rtx] (GTU (PLUS a C) (C - 1)) --> (LTU a -C)

	* simplify-rtx.c (simplify_relational_operation_1): Add transformation
	(GTU (PLUS a C) (C - 1)) --> (LTU a -C).

	* gcc.target/aarch64/gtu_to_ltu_cmp_1.c: New test.
	* gcc.target/aarch64/gtu_to_ltu_cmp_2.c: New test.

From-SVN: r240238

gcc/ChangeLog

+2016-09-19  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	* simplify-rtx.c (simplify_relational_operation_1): Add transformation
+	(GTU (PLUS a C) (C - 1)) --> (LTU a -C).
+
 2016-09-19  Segher Boessenkool  <segher@kernel.crashing.org>
 
 	* target.def (lra_p): Wordsmithing.

gcc/simplify-rtx.c

@@ -4650,6 +4650,19 @@ simplify_relational_operation_1 (enum rtx_code code, machine_mode mode,
 				      cmp_mode, XEXP (op0, 0), new_cmp);
     }
 
+  /* (GTU (PLUS a C) (C - 1)) where C is a non-zero constant can be
+     transformed into (LTU a -C).  */
+  if (code == GTU && GET_CODE (op0) == PLUS && CONST_INT_P (op1)
+      && CONST_INT_P (XEXP (op0, 1))
+      && (UINTVAL (op1) == UINTVAL (XEXP (op0, 1)) - 1)
+      && XEXP (op0, 1) != const0_rtx)
+    {
+      rtx new_cmp
+	= simplify_gen_unary (NEG, cmp_mode, XEXP (op0, 1), cmp_mode);
+      return simplify_gen_relational (LTU, mode, cmp_mode,
+				       XEXP (op0, 0), new_cmp);
+    }
+
   /* Canonicalize (LTU/GEU (PLUS a b) b) as (LTU/GEU (PLUS a b) a).  */
   if ((code == LTU || code == GEU)
       && GET_CODE (op0) == PLUS

gcc/testsuite/ChangeLog

+2016-09-19  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
+
+	* gcc.target/aarch64/gtu_to_ltu_cmp_1.c: New test.
+	* gcc.target/aarch64/gtu_to_ltu_cmp_2.c: New test.
+
 2016-09-19  Jakub Jelinek  <jakub@redhat.com>
 	    Jan Hubicka  <jh@suse.cz>
 

gcc/testsuite/gcc.target/aarch64/gtu_to_ltu_cmp_1.c

+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+int
+f1 (int x, int t)
+{
+  if (x == -1 || x == -2)
+    t = 1;
+
+  return t;
+}
+
+/* { dg-final { scan-assembler-times "cmn\\tw\[0-9\]+, #2" 1 } } */

gcc/testsuite/gcc.target/aarch64/gtu_to_ltu_cmp_2.c

+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+unsigned int
+foo (unsigned int a, unsigned int b)
+{
+  return (a + 10) > 9;
+}
+
+/* { dg-final { scan-assembler-times "cmn\\tw\[0-9\]+" 1 } } */
+/* { dg-final { scan-assembler-not "add\\tw\[0-9\]+" } } */