re PR target/25128 ([m68k] Suboptimal comparisons against 65536)

	PR target/25128
	* config/m68k/predicates.md (swap_peephole_relational_operator): New
	predicate.
	* config/m68k/m68k.md (relational tests against 65535/65536): New
	peephole2.

	PR target/25128
	* gcc.target/m68k/pr25128.c: New test.

From-SVN: r242676

gcc/ChangeLog

+2016-11-20  Jeff Law  <law@redhat.com>
+
+	PR target/25128
+	* config/m68k/predicates.md (swap_peephole_relational_operator): New
+	predicate.
+	* config/m68k/m68k.md (relational tests against 65535/65536): New
+	peephole2.
+
 2016-11-21  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* tree-ssa-loop-prefetch.c: Delete FIXME after the includes.

gcc/config/m68k/m68k.md

@@ -7786,7 +7786,6 @@
   operands[6] = GEN_INT (exact_log2 (INTVAL (operands[1]) + 1));
   operands[7] = operands[2];
 }")
-
 (define_peephole2
   [(set (cc0) (compare (match_operand:SI 0 "register_operand" "")
 		       (match_operand:SI 1 "pow2_m1_operand" "")))
@@ -7804,3 +7803,23 @@
 			   (match_dup 2) (match_dup 3)))]
   "{ operands[4] = GEN_INT (exact_log2 (INTVAL (operands[1]) + 1)); }")
 
+;; When optimizing for size or for the original 68000 or 68010, we can
+;; improve some relational tests against 65536 (which get canonicalized
+;; internally against 65535).
+;; The rotate in the output pattern will turn into a swap.
+(define_peephole2
+  [(set (cc0) (compare (match_operand:SI 0 "register_operand" "")
+		       (const_int 65535)))
+   (set (pc) (if_then_else (match_operator 1 "swap_peephole_relational_operator"
+			     [(cc0) (const_int 0)])
+			   (match_operand 2 "pc_or_label_operand")
+			   (match_operand 3 "pc_or_label_operand")))]
+  "peep2_reg_dead_p (1, operands[0])
+   && (operands[2] == pc_rtx || operands[3] == pc_rtx)
+   && (optimize_size || TUNE_68000_10)
+   && DATA_REG_P (operands[0])"
+  [(set (match_dup 0) (rotate:SI (match_dup 0) (const_int 16)))
+   (set (cc0) (compare (subreg:HI (match_dup 0) 2) (const_int 0)))
+   (set (pc) (if_then_else (match_op_dup 1 [(cc0) (const_int 0)])
+			   (match_dup 2) (match_dup 3)))]
+  "")

gcc/config/m68k/predicates.md

@@ -279,3 +279,6 @@
 ;; Used to detect (pc) or (label_ref) in some jumping patterns to cut down
 (define_predicate "pc_or_label_operand"
   (match_code "pc,label_ref"))
+
+(define_predicate "swap_peephole_relational_operator"
+  (match_code "gtu,leu,gt,le"))

gcc/testsuite/ChangeLog

+2016-11-20  Jeff Law  <law@redhat.com>
+
+	PR target/25128
+	* gcc.target/m68k/pr25128.c: New test.
+
 2016-11-21  Richard Sandiford  <richard.sandiford@arm.com>
 
 	* gcc.dg/tree-ssa/tailcall-7.c: New test.

gcc/testsuite/gcc.target/m68k/pr25128.c

+/* { dg-do compile } */
+/* { dg-options "-Os" } */
+
+/* { dg-final { scan-assembler-times "swap" 4 } } */
+/* { dg-final { scan-assembler-times "tst.w" 4 } } */
+/* { dg-final { scan-assembler-not "cmp.l" } } */
+
+
+unsigned int bar (void);
+void
+foo1 (void)
+{
+  unsigned int a = bar ();
+  if (0x10000 <= a)
+    bar ();
+}
+
+
+void
+foo2 (void)
+{
+  unsigned int a = bar ();
+  if (0x10000 > a)
+    bar ();
+}
+
+
+void
+foo3 (void)
+{
+  int a = bar ();
+  if (0x10000 <= a)
+    bar ();
+}
+
+
+void
+foo4 (void)
+{
+  int a = bar ();
+  if (0x10000 > a)
+    bar ();
+}
+
+
+
+
+