re PR tree-optimization/79390 (10% performance drop in SciMark2 LU after r242550)

	PR tree-optimization/79390
	* optabs.c (emit_conditional_move): If the preferred op2/op3 operand
	order does not result in usable sequence, retry with reversed operand
	order.

	* gcc.target/i386/pr70465-2.c: Xfail the scan-assembler-not test.

From-SVN: r246882

gcc/ChangeLog

 2017-04-12  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/79390
+	* optabs.c (emit_conditional_move): If the preferred op2/op3 operand
+	order does not result in usable sequence, retry with reversed operand
+	order.
+
 	PR sanitizer/80403
 	PR sanitizer/80404
 	PR sanitizer/80405

gcc/optabs.c

@@ -4258,12 +4258,15 @@ emit_conditional_move (rtx target, enum rtx_code code, rtx op0, rtx op1,
   if (cmode == VOIDmode)
     cmode = GET_MODE (op0);
 
+  enum rtx_code orig_code = code;
+  bool swapped = false;
   if (swap_commutative_operands_p (op2, op3)
       && ((reversed = reversed_comparison_code_parts (code, op0, op1, NULL))
           != UNKNOWN))
     {
       std::swap (op2, op3);
       code = reversed;
+      swapped = true;
     }
 
   if (mode == VOIDmode)
@@ -4272,27 +4275,28 @@ emit_conditional_move (rtx target, enum rtx_code code, rtx op0, rtx op1,
   icode = direct_optab_handler (movcc_optab, mode);
 
   if (icode == CODE_FOR_nothing)
-    return 0;
+    return NULL_RTX;
 
   if (!target)
     target = gen_reg_rtx (mode);
 
+  for (int pass = 0; ; pass++)
+    {
       code = unsignedp ? unsigned_condition (code) : code;
       comparison = simplify_gen_relational (code, VOIDmode, cmode, op0, op1);
 
       /* We can get const0_rtx or const_true_rtx in some circumstances.  Just
-     return NULL and let the caller figure out how best to deal with this
+	 punt and let the caller figure out how best to deal with this
 	 situation.  */
-  if (!COMPARISON_P (comparison))
-    return NULL_RTX;
-
+      if (COMPARISON_P (comparison))
+	{
 	  saved_pending_stack_adjust save;
 	  save_pending_stack_adjust (&save);
 	  last = get_last_insn ();
 	  do_pending_stack_adjust ();
 	  prepare_cmp_insn (XEXP (comparison, 0), XEXP (comparison, 1),
-		    GET_CODE (comparison), NULL_RTX, unsignedp, OPTAB_WIDEN,
-		    &comparison, &cmode);
+			    GET_CODE (comparison), NULL_RTX, unsignedp,
+			    OPTAB_WIDEN, &comparison, &cmode);
 	  if (comparison)
 	    {
 	      struct expand_operand ops[4];
@@ -4310,7 +4314,23 @@ emit_conditional_move (rtx target, enum rtx_code code, rtx op0, rtx op1,
 	    }
 	  delete_insns_since (last);
 	  restore_pending_stack_adjust (&save);
+	}
+
+      if (pass == 1)
+	return NULL_RTX;
+
+      /* If the preferred op2/op3 order is not usable, retry with other
+	 operand order, perhaps it will expand successfully.  */
+      if (swapped)
+	code = orig_code;
+      else if ((reversed = reversed_comparison_code_parts (orig_code, op0, op1,
+							   NULL))
+	       != UNKNOWN)
+	code = reversed;
+      else
 	return NULL_RTX;
+      std::swap (op2, op3);
+    }
 }
 
 

gcc/testsuite/ChangeLog

 2017-04-12  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/79390
+	* gcc.target/i386/pr70465-2.c: Xfail the scan-assembler-not test.
+
 	PR sanitizer/80403
 	PR sanitizer/80404
 	PR sanitizer/80405

gcc/testsuite/gcc.target/i386/pr70465-2.c

 /* PR target/70465 */
 /* { dg-do compile } */
 /* { dg-options "-Ofast -mfpmath=387 -fomit-frame-pointer" } */
-/* { dg-final { scan-assembler-not "fxch\t%st.1" } } */
+/* { dg-final { scan-assembler-not "fxch\t%st.1" { xfail *-*-* } } } */
 
 extern float d[1024];