Re: [PATCH] Fix ICE with __atomic_{always,is}_lock_free (PR middle-end/77624)

[Richard Biener <rguenther at suse dot de>]

On Tue, 20 Sep 2016, Jakub Jelinek wrote:

> Hi!
> 
> fold_builtin_atomic_always_lock_free has an assertion that if the 2nd
> argument isn't INTEGER_CST, it has POINTER_TYPE_P, but additionally for
> casts to void * it looks through the cast.  That means though for invalid
> code if an integral expression etc. is converted to pointer, we violate the
> assertion.  This patch instead doesn't look through such casts, so
> type_align is effectively alignment of void and thus it considers objects
> insufficiently aligned, but doesn't ICE.
> 
> Another approach (incomplete) is what I've attached to the PR - instead of
> prototyping __atomic_{always,is}_lock_free it uses ... and only checks that
> it has 2 arguments and that the last one is a pointer - that way we don't
> have to try to undo implicit cast to void * and know the conversion in there
> is the user conversion.  Unfortunately the C++ FE isn't prepared for the
> check_builtin_function_arguments to change the arguments (unlike C).
> 
> I've bootstrapped/regtested on x86_64-linux and i686-linux the following
> fix, ok for trunk, or should I invest more time into the other approach?

Ok for trunk.  I think the other solution would be to somehow mark the
builtin to not get the (void *) cast applied in the first place ...
(make it varargs?)

Thanks,
Richard.

> 2016-09-19  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/77624
> 	* builtins.c (fold_builtin_atomic_always_lock_free): Only look through
> 	cast to void * if the cast is from some other pointer type.
> 
> 	* c-c++-common/pr77624-1.c: New test.
> 	* c-c++-common/pr77624-2.c: New test.
> 
> --- gcc/builtins.c.jj	2016-09-16 22:19:38.000000000 +0200
> +++ gcc/builtins.c	2016-09-19 15:28:41.100412521 +0200
> @@ -5575,8 +5575,10 @@ fold_builtin_atomic_always_lock_free (tr
>  	 end before anything else has a chance to look at it.  The pointer
>  	 parameter at this point is usually cast to a void *, so check for that
>  	 and look past the cast.  */
> -      if (CONVERT_EXPR_P (arg1) && POINTER_TYPE_P (ttype)
> -	  && VOID_TYPE_P (TREE_TYPE (ttype)))
> +      if (CONVERT_EXPR_P (arg1)
> +	  && POINTER_TYPE_P (ttype)
> +	  && VOID_TYPE_P (TREE_TYPE (ttype))
> +	  && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (arg1, 0))))
>  	arg1 = TREE_OPERAND (arg1, 0);
>  
>        ttype = TREE_TYPE (arg1);
> --- gcc/testsuite/c-c++-common/pr77624-1.c.jj	2016-09-19 15:18:09.049394093 +0200
> +++ gcc/testsuite/c-c++-common/pr77624-1.c	2016-09-19 15:41:09.972949880 +0200
> @@ -0,0 +1,14 @@
> +/* PR middle-end/77624 */
> +/* { dg-do compile } */
> +
> +int
> +foo (int a)
> +{
> +  return __atomic_is_lock_free (2, a);		/* { dg-warning "pointer from integer" "" { target c } } */
> +}						/* { dg-error "invalid conversion" "" { target c++ } 7 } */
> +
> +int
> +bar (int a)
> +{
> +  return __atomic_always_lock_free (2, a);	/* { dg-warning "pointer from integer" "" { target c } } */
> +}						/* { dg-error "invalid conversion" "" { target c++ } 13 } */
> --- gcc/testsuite/c-c++-common/pr77624-2.c.jj	2016-09-19 15:18:12.280353292 +0200
> +++ gcc/testsuite/c-c++-common/pr77624-2.c	2016-09-19 15:42:37.441844581 +0200
> @@ -0,0 +1,26 @@
> +/* PR middle-end/77624 */
> +/* { dg-do compile } */
> +
> +void
> +foo (int *a)
> +{
> +  double b = 0;
> +  __atomic_is_lock_free (2, a, 2);	/* { dg-error "too many arguments" } */
> +  __atomic_is_lock_free (2);		/* { dg-error "too few arguments" } */
> +  __atomic_is_lock_free (2, b);		/* { dg-error "incompatible type" "" { target c } } */
> +					/* { dg-message "expected" "" { target c } 10 } */
> +					/* { dg-error "convert" "" { target c++ } 10 } */
> +  __atomic_is_lock_free (2, 0);
> +}
> +
> +void
> +bar (int *a)
> +{
> +  double b = 0;
> +  __atomic_always_lock_free (2, a, 2);	/* { dg-error "too many arguments" } */
> +  __atomic_always_lock_free (2);	/* { dg-error "too few arguments" } */
> +  __atomic_always_lock_free (2, b);	/* { dg-error "incompatible type" "" { target c } } */
> +					/* { dg-message "expected" "" { target c } 22 } */
> +					/* { dg-error "convert" "" { target c++ } 22 } */
> +  __atomic_always_lock_free (2, 0);
> +}
> 
> 	Jakub
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nuernberg)