re PR target/92549 (Use x86 xchg instruction more)

	PR target/92549
	* config/i386/i386.md (peephole2 for *swap<mode>): New peephole2.

	* gcc.target/i386/pr92549.c: New test.

From-SVN: r278439

gcc/ChangeLog

 2019-11-19  Jakub Jelinek  <jakub@redhat.com>
 
+	PR target/92549
+	* config/i386/i386.md (peephole2 for *swap<mode>): New peephole2.
+
 	PR middle-end/91450
 	* internal-fn.c (expand_mul_overflow): For s1 * s2 -> ur, if one
 	operand is negative and one non-negative, compare the non-negative

gcc/config/i386/i386.md

@@ -2787,6 +2787,17 @@
    (set_attr "amdfam10_decode" "double")
    (set_attr "bdver1_decode" "double")])
 
+(define_peephole2
+  [(set (match_operand:SWI 0 "register_operand")
+	(match_operand:SWI 1 "register_operand"))
+   (set (match_dup 1)
+	(match_operand:SWI 2 "register_operand"))
+   (set (match_dup 2) (match_dup 0))]
+  "peep2_reg_dead_p (3, operands[0])
+   && optimize_insn_for_size_p ()"
+  [(parallel [(set (match_dup 1) (match_dup 2))
+	      (set (match_dup 2) (match_dup 1))])])
+
 (define_expand "movstrict<mode>"
   [(set (strict_low_part (match_operand:SWI12 0 "register_operand"))
 	(match_operand:SWI12 1 "general_operand"))]

gcc/testsuite/ChangeLog

 2019-11-19  Jakub Jelinek  <jakub@redhat.com>
 
+	PR target/92549
+	* gcc.target/i386/pr92549.c: New test.
+
 	PR middle-end/91450
 	* gcc.c-torture/execute/pr91450-1.c: New test.
 	* gcc.c-torture/execute/pr91450-2.c: New test.

gcc/testsuite/gcc.target/i386/pr92549.c

+/* PR target/92549 */
+/* { dg-do compile } */
+/* { dg-options "-Os -masm=att" } */
+/* { dg-additional-options "-mregparm=2" { target ia32 } } */
+/* { dg-final { scan-assembler "xchgl" } } */
+
+__attribute__((noipa)) int
+bar (int a, int b)
+{
+  return b - a + 5;
+}
+
+int
+foo (int a, int b)
+{
+  return 1 + bar (b, a);
+}