[PATCH 2/6] ifcvt: Allow constants operands in noce_convert_multiple_sets.

[Robin Dapp <rdapp at linux dot ibm dot com>]

This patch checks whether the current target supports conditional moves
with immediate then/else operands and allows noce_convert_multiple_sets
to deal with constants subsequently.
Also, minor refactoring is performed.

--

gcc/ChangeLog:

2018-11-14  Robin Dapp  <rdapp@linux.ibm.com>

	* ifcvt.c (have_const_cmov): New function.
	(noce_convert_multiple_sets): Allow constants if supported.
	(bb_ok_for_noce_convert_multiple_sets): Likewise.
	(check_cond_move_block): Refactor.
---
 gcc/ifcvt.c | 46 ++++++++++++++++++++++++++++++++++++----------
 1 file changed, 36 insertions(+), 10 deletions(-)

diff --git a/gcc/ifcvt.c b/gcc/ifcvt.c
index ddf077fa051..660bb46eb1c 100644
--- a/gcc/ifcvt.c
+++ b/gcc/ifcvt.c
@@ -3077,6 +3077,27 @@ bb_valid_for_noce_process_p (basic_block test_bb, rtx cond,
   return false;
 }
 
+/* Check if we have a movcc pattern that accepts constants as then/else
+   operand (op 2/3).  */
+static bool
+have_const_cmov (machine_mode mode)
+{
+  enum insn_code icode;
+  if ((icode = direct_optab_handler (movcc_optab, mode))
+      != CODE_FOR_nothing)
+    {
+      if (insn_data[(int) icode].operand[2].predicate
+	  && (insn_data[(int) icode].operand[2].predicate
+	    (const1_rtx, insn_data[(int) icode].operand[2].mode)))
+	if (insn_data[(int) icode].operand[3].predicate
+	    && (insn_data[(int) icode].operand[3].predicate
+	      (const1_rtx, insn_data[(int) icode].operand[3].mode)))
+	  return true;
+    }
+
+  return false;
+}
+
 /* We have something like:
 
      if (x > y)
@@ -3194,7 +3215,12 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
 	 we'll end up trying to emit r4:HI = cond ? (r1:SI) : (r3:HI).
 	 Wrap the two cmove operands into subregs if appropriate to prevent
 	 that.  */
-      if (GET_MODE (new_val) != GET_MODE (temp))
+
+      /* Check if we can emit a cmove with constant operands.  */
+      bool allow_constants = have_const_cmov (GET_MODE (target));
+
+      if (!(allow_constants && CONST_INT_P (new_val))
+         && GET_MODE (new_val) != GET_MODE (temp))
 	{
 	  machine_mode src_mode = GET_MODE (new_val);
 	  machine_mode dst_mode = GET_MODE (temp);
@@ -3205,7 +3231,8 @@ noce_convert_multiple_sets (struct noce_if_info *if_info)
 	    }
 	  new_val = lowpart_subreg (dst_mode, new_val, src_mode);
 	}
-      if (GET_MODE (old_val) != GET_MODE (temp))
+      if (!(allow_constants && CONST_INT_P (old_val))
+         && GET_MODE (old_val) != GET_MODE (temp))
 	{
 	  machine_mode src_mode = GET_MODE (old_val);
 	  machine_mode dst_mode = GET_MODE (temp);
@@ -3339,9 +3366,10 @@ bb_ok_for_noce_convert_multiple_sets (basic_block test_bb)
       if (!REG_P (dest))
 	return false;
 
-      if (!(REG_P (src)
-	   || (GET_CODE (src) == SUBREG && REG_P (SUBREG_REG (src))
-	       && subreg_lowpart_p (src))))
+      if (!((REG_P (src)
+	      || (have_const_cmov (GET_MODE (dest)) && CONST_INT_P (src)))
+	    || (GET_CODE (src) == SUBREG && REG_P (SUBREG_REG (src))
+	      && subreg_lowpart_p (src))))
 	return false;
 
       /* Destination must be appropriate for a conditional write.  */
@@ -3689,7 +3717,7 @@ check_cond_move_block (basic_block bb,
     {
       rtx set, dest, src;
 
-      if (!NONDEBUG_INSN_P (insn) || JUMP_P (insn))
+      if (!active_insn_p (insn))
 	continue;
       set = single_set (insn);
       if (!set)
@@ -3705,10 +3733,8 @@ check_cond_move_block (basic_block bb,
       if (!CONSTANT_P (src) && !register_operand (src, VOIDmode))
 	return FALSE;
 
-      if (side_effects_p (src) || side_effects_p (dest))
-	return FALSE;
-
-      if (may_trap_p (src) || may_trap_p (dest))
+      /* Check for side effects and trapping.  */
+      if (!noce_operand_ok (src) || !noce_operand_ok (dest))
 	return FALSE;
 
       /* Don't try to handle this if the source register was
-- 
2.17.0