[PATCH] middle-end: Small __builtin_clear_padding improvements

[Jakub Jelinek <jakub@redhat.com>]

Hi!

When looking at __builtin_clear_padding today, I've noticed that
it is quite wasteful to extend the original user one argument to 3,
2 is enough.  We need to encode the original type of the first argument
because pointer conversions are useless in GIMPLE, and we need to record
a boolean whether it is for -ftrivial-auto-var-init=* or not.
But for recording the type we don't need the value (we've always used
zero) and for recording the boolean we don't need the type (we've always
used integer_type_node).
So, this patch merges the two into one.

Ok for trunk if it passes full bootstrap/regtest?

2022-02-11  Jakub Jelinek  <jakub@redhat.com>

	* tree.cc (build_common_builtin_nodes): Fix up formatting in
	__builtin_clear_padding decl creation.
	* gimplify.cc (gimple_add_padding_init_for_auto_var): Encode
	for_auto_init in the value of 2nd BUILT_IN_CLEAR_PADDING
	argument rather than in 3rd argument.
	(gimplify_call_expr): Likewise.  Fix up comment formatting.
	* gimple-fold.cc (gimple_fold_builtin_clear_padding): Expect
	2 arguments instead of 3, take for_auto_init from the value
	of 2nd argument.

--- gcc/tree.cc.jj	2022-02-11 00:19:22.436063200 +0100
+++ gcc/tree.cc	2022-02-11 12:15:00.929134203 +0100
@@ -9520,7 +9520,7 @@ build_common_builtin_nodes (void)
       local_define_builtin ("__builtin_clear_padding", ftype,
 			    BUILT_IN_CLEAR_PADDING,
 			    "__builtin_clear_padding",
-			      ECF_LEAF | ECF_NOTHROW);
+			    ECF_LEAF | ECF_NOTHROW);
     }
 
   if (!builtin_decl_explicit_p (BUILT_IN_UNREACHABLE)
--- gcc/gimplify.cc.jj	2022-02-11 00:19:22.305064981 +0100
+++ gcc/gimplify.cc	2022-02-11 12:17:22.679180223 +0100
@@ -1804,7 +1804,6 @@ gimple_add_padding_init_for_auto_var (tr
 				      gimple_seq *seq_p)
 {
   tree addr_of_decl = NULL_TREE;
-  bool for_auto_init = true;
   tree fn = builtin_decl_explicit (BUILT_IN_CLEAR_PADDING);
 
   if (is_vla)
@@ -1821,11 +1820,8 @@ gimple_add_padding_init_for_auto_var (tr
       addr_of_decl = build_fold_addr_expr (decl);
     }
 
-  gimple *call = gimple_build_call (fn,
-				    3, addr_of_decl,
-				    build_zero_cst (TREE_TYPE (addr_of_decl)),
-				    build_int_cst (integer_type_node,
-						   (int) for_auto_init));
+  gimple *call = gimple_build_call (fn, 2, addr_of_decl,
+				    build_one_cst (TREE_TYPE (addr_of_decl)));
   gimplify_seq_add_stmt (seq_p, call);
 }
 
@@ -3536,15 +3532,12 @@ gimplify_call_expr (tree *expr_p, gimple
 	  {
 	    /* Remember the original type of the argument in an internal
 	       dummy second argument, as in GIMPLE pointer conversions are
-	       useless. also mark this call as not for automatic initialization
-	       in the internal dummy third argument.  */
+	       useless.  Also mark this call as not for automatic
+	       initialization in the internal dummy third argument.  */
 	    p = CALL_EXPR_ARG (*expr_p, 0);
-	    bool for_auto_init = false;
 	    *expr_p
-	      = build_call_expr_loc (EXPR_LOCATION (*expr_p), fndecl, 3, p,
-				     build_zero_cst (TREE_TYPE (p)),
-				     build_int_cst (integer_type_node,
-						    (int) for_auto_init));
+	      = build_call_expr_loc (EXPR_LOCATION (*expr_p), fndecl, 2, p,
+				     build_zero_cst (TREE_TYPE (p)));
 	    return GS_OK;
 	  }
 	break;
--- gcc/gimple-fold.cc.jj	2022-02-11 00:18:54.799439055 +0100
+++ gcc/gimple-fold.cc	2022-02-11 12:13:27.869417000 +0100
@@ -4879,10 +4879,10 @@ gimple_fold_builtin_clear_padding (gimpl
   gcc_assert (gimple_call_num_args (stmt) == 3);
   tree ptr = gimple_call_arg (stmt, 0);
   tree typearg = gimple_call_arg (stmt, 1);
-  /* the 3rd argument of __builtin_clear_padding is to distinguish whether
-     this call is made by the user or by the compiler for automatic variable
-     initialization.  */
-  bool for_auto_init = (bool) TREE_INT_CST_LOW (gimple_call_arg (stmt, 2));
+  /* The 2nd argument of __builtin_clear_padding's value is used to
+     distinguish whether this call is made by the user or by the compiler
+     for automatic variable initialization.  */
+  bool for_auto_init = (bool) TREE_INT_CST_LOW (typearg);
   tree type = TREE_TYPE (TREE_TYPE (typearg));
   location_t loc = gimple_location (stmt);
   clear_padding_struct buf;

	Jakub