bitint: Fix up lowering of bitfield loads/stores [PR114313]

Hi!

The following testcase ICEs, because for large/huge _BitInt bitfield
loads/stores we use the DECL_BIT_FIELD_REPRESENTATIVE as the underlying
"var" and indexes into it can be larger than the precision of the
bitfield might normally allow.

The following patch fixes that by passing NULL_TREE type in that case
to limb_access, so that we always return m_limb_type type and don't
do the extra assertions, after all, the callers expect that too.
I had to add the first hunk to avoid ICE, it was using type in one place
even when it was NULL.  But TYPE_SIZE (TREE_TYPE (var)) seems like the
right size to use anyway because the code uses VIEW_CONVERT_EXPR on it.

Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

2024-03-13  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/114313
	* gimple-lower-bitint.cc (bitint_large_huge::limb_access): Use
	TYPE_SIZE of TREE_TYPE (var) rather than TYPE_SIZE of type.
	(bitint_large_huge::handle_load): Pass NULL_TREE rather than
	rhs_type to limb_access for the bitfield load cases.
	(bitint_large_huge::lower_mergeable_stmt): Pass NULL_TREE rather than
	lhs_type to limb_access if nlhs is non-NULL.

	* gcc.dg/torture/bitint-62.c: New test.


	Jakub

On Wed, 13 Mar 2024, Jakub Jelinek wrote:

> Hi!
> 
> The following testcase ICEs, because for large/huge _BitInt bitfield
> loads/stores we use the DECL_BIT_FIELD_REPRESENTATIVE as the underlying
> "var" and indexes into it can be larger than the precision of the
> bitfield might normally allow.
> 
> The following patch fixes that by passing NULL_TREE type in that case
> to limb_access, so that we always return m_limb_type type and don't
> do the extra assertions, after all, the callers expect that too.
> I had to add the first hunk to avoid ICE, it was using type in one place
> even when it was NULL.  But TYPE_SIZE (TREE_TYPE (var)) seems like the
> right size to use anyway because the code uses VIEW_CONVERT_EXPR on it.
> 
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?

OK.

Richard.
 
> 2024-03-13  Jakub Jelinek  <jakub@redhat.com>
> 
> 	PR middle-end/114313
> 	* gimple-lower-bitint.cc (bitint_large_huge::limb_access): Use
> 	TYPE_SIZE of TREE_TYPE (var) rather than TYPE_SIZE of type.
> 	(bitint_large_huge::handle_load): Pass NULL_TREE rather than
> 	rhs_type to limb_access for the bitfield load cases.
> 	(bitint_large_huge::lower_mergeable_stmt): Pass NULL_TREE rather than
> 	lhs_type to limb_access if nlhs is non-NULL.
> 
> 	* gcc.dg/torture/bitint-62.c: New test.
> 
> --- gcc/gimple-lower-bitint.cc.jj	2024-03-05 10:27:04.609415622 +0100
> +++ gcc/gimple-lower-bitint.cc	2024-03-12 16:45:50.152914901 +0100
> @@ -640,7 +640,7 @@ bitint_large_huge::limb_access (tree typ
>  					 TREE_TYPE (TREE_TYPE (var))))
>  	{
>  	  unsigned HOST_WIDE_INT nelts
> -	    = CEIL (tree_to_uhwi (TYPE_SIZE (type)), limb_prec);
> +	    = CEIL (tree_to_uhwi (TYPE_SIZE (TREE_TYPE (var))), limb_prec);
>  	  tree atype = build_array_type_nelts (ltype, nelts);
>  	  var = build1 (VIEW_CONVERT_EXPR, atype, var);
>  	}
> @@ -1854,7 +1854,7 @@ bitint_large_huge::handle_load (gimple *
>  		m_gsi = gsi_after_labels (gsi_bb (m_gsi));
>  	      else
>  		gsi_next (&m_gsi);
> -	      tree t = limb_access (rhs_type, nrhs1, size_int (bo_idx), true);
> +	      tree t = limb_access (NULL_TREE, nrhs1, size_int (bo_idx), true);
>  	      tree iv = make_ssa_name (m_limb_type);
>  	      g = gimple_build_assign (iv, t);
>  	      insert_before (g);
> @@ -1941,7 +1941,7 @@ bitint_large_huge::handle_load (gimple *
>        tree iv2 = NULL_TREE;
>        if (nidx0)
>  	{
> -	  tree t = limb_access (rhs_type, nrhs1, nidx0, true);
> +	  tree t = limb_access (NULL_TREE, nrhs1, nidx0, true);
>  	  iv = make_ssa_name (m_limb_type);
>  	  g = gimple_build_assign (iv, t);
>  	  insert_before (g);
> @@ -1966,7 +1966,7 @@ bitint_large_huge::handle_load (gimple *
>  	      if_then (g, profile_probability::likely (),
>  		       edge_true, edge_false);
>  	    }
> -	  tree t = limb_access (rhs_type, nrhs1, nidx1, true);
> +	  tree t = limb_access (NULL_TREE, nrhs1, nidx1, true);
>  	  if (m_upwards_2limb
>  	      && !m_first
>  	      && !m_bitfld_load
> @@ -2728,8 +2728,8 @@ bitint_large_huge::lower_mergeable_stmt
>  	      /* Otherwise, stores to any other lhs.  */
>  	      if (!done)
>  		{
> -		  tree l = limb_access (lhs_type, nlhs ? nlhs : lhs,
> -					nidx, true);
> +		  tree l = limb_access (nlhs ? NULL_TREE : lhs_type,
> +					nlhs ? nlhs : lhs, nidx, true);
>  		  g = gimple_build_assign (l, rhs1);
>  		}
>  	      insert_before (g);
> @@ -2873,7 +2873,8 @@ bitint_large_huge::lower_mergeable_stmt
>  	  /* Otherwise, stores to any other lhs.  */
>  	  if (!done)
>  	    {
> -	      tree l = limb_access (lhs_type, nlhs ? nlhs : lhs, nidx, true);
> +	      tree l = limb_access (nlhs ? NULL_TREE : lhs_type,
> +				    nlhs ? nlhs : lhs, nidx, true);
>  	      g = gimple_build_assign (l, rhs1);
>  	    }
>  	  insert_before (g);
> --- gcc/testsuite/gcc.dg/torture/bitint-62.c.jj	2024-03-12 16:40:38.400198787 +0100
> +++ gcc/testsuite/gcc.dg/torture/bitint-62.c	2024-03-12 16:41:43.988297525 +0100
> @@ -0,0 +1,28 @@
> +/* PR middle-end/114313 */
> +/* { dg-do run { target bitint } } */
> +/* { dg-options "-std=c23" } */
> +/* { dg-skip-if "" { ! run_expensive_tests }  { "*" } { "-O0" "-O2" } } */
> +/* { dg-skip-if "" { ! run_expensive_tests } { "-flto" } { "" } } */
> +
> +#if __BITINT_MAXWIDTH__ >= 256
> +struct S { _BitInt(257) : 257; _BitInt(256) b : 182; } s;
> +
> +__attribute__((noipa)) _BitInt(256)
> +foo (void)
> +{
> +  return s.b;
> +}
> +#endif
> +
> +int
> +main ()
> +{
> +#if __BITINT_MAXWIDTH__ >= 256
> +  s.b = 1414262180967678524960294186228886540125217087586381431wb;
> +  if (foo () != 1414262180967678524960294186228886540125217087586381431wb)
> +    __builtin_abort ();
> +  s.b = -581849792837428541666755934071828568425158644418477999wb;
> +  if (foo () != -581849792837428541666755934071828568425158644418477999wb)
> +    __builtin_abort ();
> +#endif
> +}
> 
> 	Jakub
> 
>