Canonicalize argument order for commutative functions

This patch uses information about internal functions to canonicalize
the argument order of calls.

gcc/
	* gimple-fold.c: Include internal-fn.h.
	(fold_stmt_1): If a function maps to an internal one, use
	first_commutative_argument to canonicalize the order of
	commutative arguments.
	* gimple-match-head.c (gimple_resimplify2, gimple_resimplify3)
	(gimple_resimplify4, gimple_resimplify5): Extend commutativity
	checks to functions.

gcc/testsuite/
	* gcc.dg/fmax-fmin-1.c: New test.

gcc/gimple-fold.c

@@ -69,6 +69,7 @@ along with GCC; see the file COPYING3.  If not see
 #include "varasm.h"
 #include "memmodel.h"
 #include "optabs.h"
+#include "internal-fn.h"
 
 enum strlen_range_kind {
   /* Compute the exact constant string length.  */
@@ -6109,18 +6110,36 @@ fold_stmt_1 (gimple_stmt_iterator *gsi, bool inplace, tree (*valueize) (tree))
       break;
     case GIMPLE_CALL:
       {
-	for (i = 0; i < gimple_call_num_args (stmt); ++i)
+	gcall *call = as_a<gcall *> (stmt);
+	for (i = 0; i < gimple_call_num_args (call); ++i)
 	  {
-	    tree *arg = gimple_call_arg_ptr (stmt, i);
+	    tree *arg = gimple_call_arg_ptr (call, i);
 	    if (REFERENCE_CLASS_P (*arg)
 		&& maybe_canonicalize_mem_ref_addr (arg))
 	      changed = true;
 	  }
-	tree *lhs = gimple_call_lhs_ptr (stmt);
+	tree *lhs = gimple_call_lhs_ptr (call);
 	if (*lhs
 	    && REFERENCE_CLASS_P (*lhs)
 	    && maybe_canonicalize_mem_ref_addr (lhs))
 	  changed = true;
+	if (*lhs)
+	  {
+	    combined_fn cfn = gimple_call_combined_fn (call);
+	    internal_fn ifn = associated_internal_fn (cfn, TREE_TYPE (*lhs));
+	    int opno = first_commutative_argument (ifn);
+	    if (opno >= 0)
+	      {
+		tree arg1 = gimple_call_arg (call, opno);
+		tree arg2 = gimple_call_arg (call, opno + 1);
+		if (tree_swap_operands_p (arg1, arg2))
+		  {
+		    gimple_call_set_arg (call, opno, arg2);
+		    gimple_call_set_arg (call, opno + 1, arg1);
+		    changed = true;
+		  }
+	      }
+	  }
 	break;
       }
     case GIMPLE_ASM:

gcc/gimple-match-head.c

@@ -294,18 +294,16 @@ gimple_resimplify2 (gimple_seq *seq, gimple_match_op *res_op,
 
   /* Canonicalize operand order.  */
   bool canonicalized = false;
-  if (res_op->code.is_tree_code ())
+  bool is_comparison
+    = (res_op->code.is_tree_code ()
+       && TREE_CODE_CLASS (tree_code (res_op->code)) == tcc_comparison);
+  if ((is_comparison || commutative_binary_op_p (res_op->code, res_op->type))
+      && tree_swap_operands_p (res_op->ops[0], res_op->ops[1]))
     {
-      auto code = tree_code (res_op->code);
-      if ((TREE_CODE_CLASS (code) == tcc_comparison
-	   || commutative_tree_code (code))
-	  && tree_swap_operands_p (res_op->ops[0], res_op->ops[1]))
-	{
-	  std::swap (res_op->ops[0], res_op->ops[1]);
-	  if (TREE_CODE_CLASS (code) == tcc_comparison)
-	    res_op->code = swap_tree_comparison (code);
-	  canonicalized = true;
-	}
+      std::swap (res_op->ops[0], res_op->ops[1]);
+      if (is_comparison)
+	res_op->code = swap_tree_comparison (tree_code (res_op->code));
+      canonicalized = true;
     }
 
   /* Limit recursion, see gimple_resimplify1.  */
@@ -376,11 +374,11 @@ gimple_resimplify3 (gimple_seq *seq, gimple_match_op *res_op,
 
   /* Canonicalize operand order.  */
   bool canonicalized = false;
-  if (res_op->code.is_tree_code ()
-      && commutative_ternary_tree_code (tree_code (res_op->code))
-      && tree_swap_operands_p (res_op->ops[0], res_op->ops[1]))
+  int argno = first_commutative_argument (res_op->code, res_op->type);
+  if (argno >= 0
+      && tree_swap_operands_p (res_op->ops[argno], res_op->ops[argno + 1]))
     {
-      std::swap (res_op->ops[0], res_op->ops[1]);
+      std::swap (res_op->ops[argno], res_op->ops[argno + 1]);
       canonicalized = true;
     }
 
@@ -424,6 +422,16 @@ gimple_resimplify4 (gimple_seq *seq, gimple_match_op *res_op,
 {
   /* No constant folding is defined for four-operand functions.  */
 
+  /* Canonicalize operand order.  */
+  bool canonicalized = false;
+  int argno = first_commutative_argument (res_op->code, res_op->type);
+  if (argno >= 0
+      && tree_swap_operands_p (res_op->ops[argno], res_op->ops[argno + 1]))
+    {
+      std::swap (res_op->ops[argno], res_op->ops[argno + 1]);
+      canonicalized = true;
+    }
+
   /* Limit recursion, see gimple_resimplify1.  */
   static unsigned depth;
   if (depth > 10)
@@ -450,7 +458,7 @@ gimple_resimplify4 (gimple_seq *seq, gimple_match_op *res_op,
   if (maybe_resimplify_conditional_op (seq, res_op, valueize))
     return true;
 
-  return false;
+  return canonicalized;
 }
 
 /* Helper that matches and simplifies the toplevel result from
@@ -465,6 +473,16 @@ gimple_resimplify5 (gimple_seq *seq, gimple_match_op *res_op,
 {
   /* No constant folding is defined for five-operand functions.  */
 
+  /* Canonicalize operand order.  */
+  bool canonicalized = false;
+  int argno = first_commutative_argument (res_op->code, res_op->type);
+  if (argno >= 0
+      && tree_swap_operands_p (res_op->ops[argno], res_op->ops[argno + 1]))
+    {
+      std::swap (res_op->ops[argno], res_op->ops[argno + 1]);
+      canonicalized = true;
+    }
+
   gimple_match_op res_op2 (*res_op);
   if (gimple_simplify (&res_op2, seq, valueize,
 		       res_op->code, res_op->type,
@@ -478,7 +496,7 @@ gimple_resimplify5 (gimple_seq *seq, gimple_match_op *res_op,
   if (maybe_resimplify_conditional_op (seq, res_op, valueize))
     return true;
 
-  return false;
+  return canonicalized;
 }
 
 /* Match and simplify the toplevel valueized operation THIS.

gcc/testsuite/gcc.dg/fmax-fmin-1.c

@@ -0,0 +1,18 @@
+/* { dg-options "-O -fdump-tree-optimized" } */
+
+void
+f1 (double *res, double x, double y)
+{
+  res[0] = __builtin_fmax (x, y);
+  res[1] = __builtin_fmax (y, x);
+}
+
+void
+f2 (double *res, double x, double y)
+{
+  res[0] = __builtin_fmin (x, y);
+  res[1] = __builtin_fmin (y, x);
+}
+
+/* { dg-final { scan-tree-dump-times {__builtin_fmax} 1 "optimized" } } */
+/* { dg-final { scan-tree-dump-times {__builtin_fmin} 1 "optimized" } } */