middle-end: Small __builtin_clear_padding improvements

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.


	Jakub

On Fri, 11 Feb 2022, Jakub Jelinek wrote:

> 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?

OK.

Thanks,
Richard.

> 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
> 
>