Re: [PATCH] builtins: Fix fold_builtin_query clzg/ctzg side-effects handling [PR112639]

[Richard Biener <rguenther@suse.de>]

On Tue, 21 Nov 2023, Jakub Jelinek wrote:

> Hi!
> 
> As the testcase shows, I've missed one spot where initially the code thinks
> it could use 2 argument IFN_CLZ/IFN_CTZ form, but then verifies it can't
> because it doesn't have the right target value and turns it into the
> arg0 ? arg1 : .C[LT]Z (arg0)
> form.  That form evaluates the argument twice though and so needs save_expr,
> which I've missed to call in that case.  In other cases where it is known
> from the beginning that it will be needed (e.g. the __builtin_clzg case
> on types smaller than unsigned int where we'll need to add an addend
> to the clz value) or the unsigned __int128 expansion called save_expr
> before.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

> 2023-11-21  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/112639
> 	* builtins.cc (fold_builtin_bit_query): If arg0 has side-effects, arg1
> 	is specified but cleared, call save_expr on arg0.
> 
> 	* gcc.dg/torture/pr112639.c: New test.
> 
> --- gcc/builtins.cc.jj	2023-11-20 10:36:18.642625716 +0100
> +++ gcc/builtins.cc	2023-11-20 15:25:59.665718971 +0100
> @@ -9819,6 +9819,8 @@ fold_builtin_bit_query (location_t loc,
>  	  if (!direct_internal_fn_supported_p (ifn, arg0_type,
>  					       OPTIMIZE_FOR_BOTH))
>  	    arg2 = NULL_TREE;
> +	  if (arg2 == NULL_TREE)
> +	    arg0 = save_expr (arg0);
>  	}
>        if (fcodei == END_BUILTINS || arg2)
>  	call = build_call_expr_internal_loc (loc, ifn, integer_type_node,
> --- gcc/testsuite/gcc.dg/torture/pr112639.c.jj	2023-11-20 15:32:24.994391656 +0100
> +++ gcc/testsuite/gcc.dg/torture/pr112639.c	2023-11-20 15:34:14.395882993 +0100
> @@ -0,0 +1,34 @@
> +/* PR middle-end/112639 */
> +/* { dg-do run } */
> +
> +unsigned long long b = 0;
> +
> +int
> +foo (void)
> +{
> +  return __builtin_clzg (b++, __SIZEOF_LONG_LONG__ * __CHAR_BIT__);
> +}
> +
> +int
> +bar (void)
> +{
> +  return __builtin_ctzg (b++, __SIZEOF_LONG_LONG__ * __CHAR_BIT__);
> +}
> +
> +int
> +main ()
> +{
> +  if (foo () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ || b != 1)
> +    __builtin_abort ();
> +  if (foo () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ - 1 || b != 2)
> +    __builtin_abort ();
> +  if (foo () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ - 2 || b != 3)
> +    __builtin_abort ();
> +  b = 0;
> +  if (bar () != __SIZEOF_LONG_LONG__ * __CHAR_BIT__ || b != 1)
> +    __builtin_abort ();
> +  if (bar () != 0 || b != 2)
> +    __builtin_abort ();
> +  if (bar () != 1 || b != 3)
> +    __builtin_abort ();
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE Software Solutions Germany GmbH,
Frankenstrasse 146, 90461 Nuernberg, Germany;
GF: Ivo Totev, Andrew McDonald, Werner Knoblich; (HRB 36809, AG Nuernberg)