On Wed, 10 Feb 2016, Jakub Jelinek wrote:
> Hi!
>
> Markus has pointed out to a reduced testcase which still ICEs even with the
> PR69241 fix. In that case the function with TREE_ADDRESSABLE return type
> does not return at all (and -Wreturn-type properly diagnoses it).
> For that case the following patch just forces the lhs on the *.part.*
> call, so that we don't ICE in assign_temp.
>
> Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
Um... I wonder if it wouldn't be better to force such functions to
be noreturn by say, placing a __builtin_unreachable () at the missing
return and maybe even adjust the return type.
In the frontend I mean.
After all, what would the code below do at runtime? Unhelpfully
write to a random memory location. So if then I'd rather
dereference literal zero here (well, not sure what to do for
-fno-delete-null-pointer targets). Otherwise this becomes a bigger
security issue than not initializing the not used return value?
The other option is to simply not split the function in this case.
Richard.
> 2016-02-10 Jakub Jelinek <ja...@redhat.com>
>
> PR ipa/69241
> * ipa-split.c (split_function): If split part returns TREE_ADDRESSABLE
> type by reference, force lhs on the call.
>
> * g++.dg/ipa/pr69241-4.C: New test.
>
> --- gcc/ipa-split.c.jj 2016-02-10 16:05:37.000000000 +0100
> +++ gcc/ipa-split.c 2016-02-10 17:18:12.553061670 +0100
> @@ -1589,7 +1589,20 @@ split_function (basic_block return_bb, s
> }
> }
> else
> - gsi_insert_after (&gsi, call, GSI_NEW_STMT);
> + {
> + /* Force a lhs if the split part has to return a value. */
> + if (split_point->split_part_set_retval
> + && DECL_BY_REFERENCE (DECL_RESULT (current_function_decl)))
> + {
> + retval = DECL_RESULT (current_function_decl);
> + if (TREE_ADDRESSABLE (TREE_TYPE (TREE_TYPE (retval))))
> + {
> + retval = get_or_create_ssa_default_def (cfun, retval);
> + gimple_call_set_lhs (call, build_simple_mem_ref (retval));
> + }
> + }
> + gsi_insert_after (&gsi, call, GSI_NEW_STMT);
> + }
> if (tsan_func_exit_call)
> gsi_insert_after (&gsi, tsan_func_exit_call, GSI_NEW_STMT);
> }
> --- gcc/testsuite/g++.dg/ipa/pr69241-4.C.jj 2016-02-10 17:22:03.977866326
> +0100
> +++ gcc/testsuite/g++.dg/ipa/pr69241-4.C 2016-02-10 17:22:00.073920229
> +0100
> @@ -0,0 +1,55 @@
> +// PR ipa/69241
> +// { dg-do compile { target c++11 } }
> +// { dg-options "-O2 -Wno-return-type" }
> +
> +template <typename> class A;
> +struct B {
> + using pointer = int *;
> +};
> +template <typename _CharT, typename = A<_CharT>> class basic_string {
> + long _M_string_length;
> + enum { _S_local_capacity = 15 } _M_local_buf[_S_local_capacity];
> + B::pointer _M_local_data;
> +
> +public:
> + ~basic_string();
> +};
> +template <typename _CharT, typename _Traits, typename _Alloc>
> +int operator<<(_Traits, basic_string<_CharT, _Alloc>);
> +class C {
> + basic_string<A<char>> _M_string;
> +};
> +class D {
> + C _M_stringbuf;
> +};
> +class F {
> + int stream;
> + D stream_;
> +};
> +class G {
> +public:
> + void operator&(int);
> +};
> +class H {
> +public:
> + H(unsigned);
> + H(H &&);
> + bool m_fn1();
> +};
> +class I {
> + void m_fn2(const int &&);
> + static H m_fn3(const int &);
> +};
> +template <typename Functor> void Bind(Functor);
> +class J {
> +public:
> + static basic_string<char> m_fn4();
> +};
> +int a;
> +void I::m_fn2(const int &&) { Bind(m_fn3); }
> +H I::m_fn3(const int &) {
> + !false ? (void)0 : G() & F() << J::m_fn4();
> + H b(a);
> + if (b.m_fn1())
> + F();
> +}
>
> Jakub
>
>
--
Richard Biener <rguent...@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Graham Norton, HRB
21284 (AG Nuernberg)
