Re: [C++ PATCH] Fix vector_size handling in templates (PR c++/35758)

[Jakub Jelinek <jakub at redhat dot com>]

On Tue, Apr 01, 2008 at 09:43:49AM -0700, Mark Mitchell wrote:
> Andrew Pinski wrote:
> 
> >I will explain what happens here. First we mark the attribute as being 
> >expanded late so we have a type of float in the function agrument; then 
> >at overload time, we don't resolve the attribute. As shown by a 
> >different testcase in the bug report which I mention in this bug report, 
> >we should be resolving the attributes at overload time so I disagree 
> >with Jakub's patch.
> 
> That was my thinking too.  Overload resolution requires instantiation of 
> template arguments in the parameter types, and, for us, that includes 
> late attributes.

You're right, my patch doesn't cure e.g.:

// PR c++/35758
// { dg-do compile }

#define vector __attribute__((vector_size(16)))

template<typename T> vector signed int foo (vector T value) {}

template<typename T> void foo (T value) {}

int
main ()
{
  vector float v;
  float f;
  foo<float> (v);
  foo<float> (f);
}

fn_type_unification calls:

      processing_template_decl += incomplete;
      fntype = tsubst (fntype, converted_args, tf_none, NULL_TREE);
      processing_template_decl -= incomplete;

which doesn't apply late template attributes to either TREE_TYPE (fntype),
nor TYPE_ARG_TYPES (fntype), because the attributes aren't actually
TYPE_ATTRIBUTES on those types, but DECL_ATTRIBUTES on
DECL_TEMPLATE_RESULT (fn) for the return type resp. individual
DECL_ARGUMENTS (DECL_TEMPLATE_RESULT (fn)), and the attributes have
type_required set, so they apply to the PARM_DECL types resp. result
type.
So, to make fn_type_unification work, I'm afraid we need something like
-      fntype = tsubst (fntype, converted_args, tf_none, NULL_TREE);
+      parms = tsubst (DECL_ARGUMENTS (DECL_TEMPLATE_RESULT (fn), converted_args, tf_none, NULL_TREE);
+      fntype_args = recreate_type_arg_types_from_parm_decl_types (parms, TREE_TYPE_ARGS (fntype));
+      fntype_rettype = tsubst (TREE_TYPE (fntype), converted_args, tf_none, NULL_TREE);
+      apply_late_template_args (&fntype_rettype, DECL_ATTRIBUTES (DECL_TEMPLATE_RESULT (fn)), 0, converted_args, tf_none, NULL_TREE);
and then use fntype_args instead of TYPE_ARG_TYPES (fntype) and
fntype_rettype instead of TREE_TYPE (fntype) later on in the function.

Plus I think something like recreate_type_arg_types_from_parm_decl_types
would be needed for tsubst_decl as well, because from what
I can see ATM TYPE_ARG_TYPES aren't being updated.  Consider
#define vector __attribute__((vector_size(16)))

vector signed int p;

template<typename T>
struct S
{
  vector signed int foo (vector T *value) { vector float *f = value; return p; }
};

int
main ()
{
  S<float> s;
  s.foo (__null);
}

where middle-end sees:
 <function_decl 0x2aaaaea7a410 foo
    type <method_type 0x2aaaaea876c0
        type <vector_type 0x2aaaaea209c0 type <integer_type 0x2aaaae93b540 int>
            type_6 V4SI
            size <integer_cst 0x2aaaae928d80 constant invariant 128>
            unit size <integer_cst 0x2aaaae928db0 constant invariant 16>
            align 128 symtab 0 alias set -1 canonical type 0x2aaaaea209c0 nunits 4>
        QI
        size <integer_cst 0x2aaaae928780 constant invariant 8>
        unit size <integer_cst 0x2aaaae9287b0 constant invariant 1>
        align 8 symtab 0 alias set -1 canonical type 0x2aaaaea876c0 method basetype <record_type 0x2aaaaea83b40 S>
        arg-types <tree_list 0x2aaaaea84bd0 value <pointer_type 0x2aaaaea83d80>
            chain <tree_list 0x2aaaaea849f0 value <pointer_type 0x2aaaae94bd80>
                chain <tree_list 0x2aaaae9498a0 value <void_type 0x2aaaae94b840 void>>>>
        pointer_to_this <pointer_type 0x2aaaaea87840>>
    arguments <parm_decl 0x2aaaae92ec60 this
...
        chain <parm_decl 0x2aaaae92ecf0 value type <pointer_type 0x2aaaaea87300>
...

where 0x2aaaaea87300 used in
TREE_TYPE (TREE_CHAIN (DECL_ARGUMENTS (current_function_decl))) is:
 <pointer_type 0x2aaaaea87300
    type <vector_type 0x2aaaaea203c0
        type <real_type 0x2aaaae94bb40 float type_6 SF
while 0x2aaaae94bd80 used as
TREE_VALUE (TREE_CHAIN (TYPE_ARG_TYPES (TREE_TYPE (current_function_decl)))) is:
 <pointer_type 0x2aaaae94bd80
    type <real_type 0x2aaaae94bb40 float type_6 SF

	Jakub