Ping.
On Wed, Mar 09, 2016 at 04:55:23PM +0100, Marek Polacek wrote:
> On Wed, Mar 09, 2016 at 04:31:37PM +0100, Jakub Jelinek wrote:
> > No, I meant:
> > switch (n)
> > {
> > struct S x;
> > case 1:
> > fn ();
> > break;
> > case 2:
> > fn2 ();
> > break;
> > case 3:
> > x = fn ();
> > if (x.a[0] != 42)
> > __builtin_abort ();
> > break;
> > case 4:
> > if (fn ().a[0] != 42)
> > __builtin_abort ();
> > break;
> > ...
> >
> > The reason is that anything after a noreturn call can be optimized away
> > shortly afterwards. Perhaps you want __attribute__((noinline, noclone)) on
> > the function too just in case (I know you haven't included -O*).
>
> Aha. I couldn't do exactly this because of
> error: switch jumps into scope of identifier with variably modified type
> so I moved the decl out of the switch.
>
> > Otherwise LGTM.
>
> Thanks.
>
> Bootstrapped/regtested on x86_64-linux.
>
> 2016-03-09 Marek Polacek <pola...@redhat.com>
>
> PR c/70093
> * c-typeck.c (build_function_call_vec): Create a TARGET_EXPR for
> nested functions returning VM types.
>
> * cgraphunit.c (cgraph_node::expand_thunk): Also build call to the
> function being thunked if the result type doesn't have fixed size.
> * gimplify.c (gimplify_modify_expr): Also set LHS if the result type
> doesn't have fixed size.
>
> * gcc.dg/nested-func-10.c: New test.
> * gcc.dg/nested-func-9.c: New test.
>
> diff --git gcc/c/c-typeck.c gcc/c/c-typeck.c
> index 6aa0f03..de9d465 100644
> --- gcc/c/c-typeck.c
> +++ gcc/c/c-typeck.c
> @@ -3068,6 +3068,16 @@ build_function_call_vec (location_t loc,
> vec<location_t> arg_loc,
> result = build_call_array_loc (loc, TREE_TYPE (fntype),
> function, nargs, argarray);
>
> + /* In this improbable scenario, a nested function returns a VM type.
> + Create a TARGET_EXPR so that the call always has a LHS, much as
> + what the C++ FE does for functions returning non-PODs. */
> + if (variably_modified_type_p (TREE_TYPE (fntype), NULL_TREE))
> + {
> + tree tmp = create_tmp_var_raw (TREE_TYPE (fntype));
> + result = build4 (TARGET_EXPR, TREE_TYPE (fntype), tmp, result,
> + NULL_TREE, NULL_TREE);
> + }
> +
> if (VOID_TYPE_P (TREE_TYPE (result)))
> {
> if (TYPE_QUALS (TREE_TYPE (result)) != TYPE_UNQUALIFIED)
> diff --git gcc/cgraphunit.c gcc/cgraphunit.c
> index 8b3fddc..4351ae4 100644
> --- gcc/cgraphunit.c
> +++ gcc/cgraphunit.c
> @@ -1708,7 +1708,9 @@ cgraph_node::expand_thunk (bool output_asm_thunks, bool
> force_gimple_thunk)
>
> /* Build call to the function being thunked. */
> if (!VOID_TYPE_P (restype)
> - && (!alias_is_noreturn || TREE_ADDRESSABLE (restype)))
> + && (!alias_is_noreturn
> + || TREE_ADDRESSABLE (restype)
> + || TREE_CODE (TYPE_SIZE_UNIT (restype)) != INTEGER_CST))
> {
> if (DECL_BY_REFERENCE (resdecl))
> {
> diff --git gcc/gimplify.c gcc/gimplify.c
> index b331e41..692d168 100644
> --- gcc/gimplify.c
> +++ gcc/gimplify.c
> @@ -4838,7 +4838,8 @@ gimplify_modify_expr (tree *expr_p, gimple_seq *pre_p,
> gimple_seq *post_p,
> }
> notice_special_calls (call_stmt);
> if (!gimple_call_noreturn_p (call_stmt)
> - || TREE_ADDRESSABLE (TREE_TYPE (*to_p)))
> + || TREE_ADDRESSABLE (TREE_TYPE (*to_p))
> + || TREE_CODE (TYPE_SIZE_UNIT (TREE_TYPE (*to_p))) != INTEGER_CST)
> gimple_call_set_lhs (call_stmt, *to_p);
> assign = call_stmt;
> }
> diff --git gcc/testsuite/gcc.dg/nested-func-10.c
> gcc/testsuite/gcc.dg/nested-func-10.c
> index e69de29..ac6f76f 100644
> --- gcc/testsuite/gcc.dg/nested-func-10.c
> +++ gcc/testsuite/gcc.dg/nested-func-10.c
> @@ -0,0 +1,56 @@
> +/* PR c/70093 */
> +/* { dg-do compile } */
> +/* { dg-options "" } */
> +
> +void __attribute__((noinline, noclone))
> +foo (int n)
> +{
> + struct S { int a[n]; };
> +
> + struct S __attribute__((noreturn))
> + fn (void)
> + {
> + __builtin_abort ();
> + }
> +
> + auto struct S __attribute__((noreturn))
> + fn2 (void)
> + {
> + __builtin_abort ();
> + }
> +
> + struct S x;
> + __typeof__ (fn ()) *p = &x;
> + switch (n)
> + {
> + case 1:
> + fn ();
> + break;
> + case 2:
> + fn2 ();
> + break;
> + case 3:
> + x = fn ();
> + if (x.a[0] != 42)
> + __builtin_abort ();
> + break;
> + case 4:
> + if (fn ().a[0] != 42)
> + __builtin_abort ();
> + break;
> + case 5:
> + if (p->a[0] != 42)
> + __builtin_abort ();
> + break;
> + case 6:
> + if (fn2 ().a[0] != 42)
> + __builtin_abort ();
> + break;
> + }
> +}
> +
> +int
> +main (void)
> +{
> + foo (1);
> +}
> diff --git gcc/testsuite/gcc.dg/nested-func-9.c
> gcc/testsuite/gcc.dg/nested-func-9.c
> index e69de29..902c258 100644
> --- gcc/testsuite/gcc.dg/nested-func-9.c
> +++ gcc/testsuite/gcc.dg/nested-func-9.c
> @@ -0,0 +1,47 @@
> +/* PR c/70093 */
> +/* { dg-do run } */
> +/* { dg-options "" } */
> +
> +void
> +foo (int n)
> +{
> + struct S { int a[n]; };
> +
> + struct S
> + fn (void)
> + {
> + struct S s;
> + s.a[0] = 42;
> + return s;
> + }
> +
> + auto struct S
> + fn2 (void)
> + {
> + return fn ();
> + }
> +
> + struct S x;
> + fn ();
> + fn2 ();
> + x = fn ();
> +
> + if (x.a[0] != 42)
> + __builtin_abort ();
> +
> + if (fn ().a[0] != 42)
> + __builtin_abort ();
> +
> + __typeof__ (fn ()) *p = &x;
> + if (p->a[0] != 42)
> + __builtin_abort ();
> +
> + if (fn2 ().a[0] != 42)
> + __builtin_abort ();
> +}
> +
> +int
> +main (void)
> +{
> + foo (1);
> +}
>
> Marek
Marek
