[Bug c++/59759] internal compiler error: in unify, using std::enable_if on classes

["trippels at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59759

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-09-26
                 CC|                            |trippels at gcc dot gnu.org
   Target Milestone|---                         |4.8.4
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.3, 4.9.1, 5.0

--- Comment #7 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
markus@x4 tmp % cat test3.ii
namespace std {
template <typename _Tp>
struct B {
  static constexpr _Tp value = 0;
};
typedef B<int> false_type;
struct C : false_type {};
template <typename>
struct is_integral : C {};
template <int, typename _Tp>
struct enable_if {
  typedef _Tp type;
};
}
enum class enabled;
constexpr enabled dummy{};
template <typename T, typename std::enable_if<std::is_integral<T>::value,
                                              enabled>::type = dummy>
class A;
template <typename T>
void f(A<T>*) {
  A<int>* map;
  f(map);
}

markus@x4 tmp % g++ -c -std=c++11 test3.ii
test3.ii: In substitution of ‘template<class T> void f(A<T>*) [with T =
<missing>]’:
test3.ii:23:8:   required from here
test3.ii:23:8: internal compiler error: in unify, at cp/pt.c:18392
   f(map);
        ^
0x606105 unify
        ../../gcc/gcc/cp/pt.c:18392
0x6067a4 unify
        ../../gcc/gcc/cp/pt.c:18234
0x51d9b8 try_class_unification
        ../../gcc/gcc/cp/pt.c:17248
0x605b77 unify
        ../../gcc/gcc/cp/pt.c:18271
0x605d5c unify
        ../../gcc/gcc/cp/pt.c:18138
0x6093f4 unify_one_argument
        ../../gcc/gcc/cp/pt.c:16657
0x60baea type_unification_real
        ../../gcc/gcc/cp/pt.c:16728
0x614aac fn_type_unification(tree_node*, tree_node*, tree_node*, tree_node*
const*, unsigned int, tree_node*, unification_kind_t, int, bool, bool)
        ../../gcc/gcc/cp/pt.c:16164
0x5843e9 add_template_candidate_real
        ../../gcc/gcc/cp/call.c:3025
0x584e5c add_template_candidate
        ../../gcc/gcc/cp/call.c:3122
0x584e5c add_candidates
        ../../gcc/gcc/cp/call.c:5253
0x587413 perform_overload_resolution
        ../../gcc/gcc/cp/call.c:3971
0x5897da build_new_function_call(tree_node*, vec<tree_node*, va_gc,
vl_embed>**, bool, int)
        ../../gcc/gcc/cp/call.c:4048
0x7032ac finish_call_expr(tree_node*, vec<tree_node*, va_gc, vl_embed>**, bool,
bool, int)
        ../../gcc/gcc/cp/semantics.c:2366
0x688c55 cp_parser_postfix_expression
        ../../gcc/gcc/cp/parser.c:6232
0x68bb09 cp_parser_unary_expression
        ../../gcc/gcc/cp/parser.c:7293
0x68c744 cp_parser_binary_expression
        ../../gcc/gcc/cp/parser.c:8035
0x68ccd9 cp_parser_assignment_expression
        ../../gcc/gcc/cp/parser.c:8278
0x68f4c4 cp_parser_expression
        ../../gcc/gcc/cp/parser.c:8440
0x68fcfc cp_parser_expression_statement
        ../../gcc/gcc/cp/parser.c:9828
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.
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From: "jamborm at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/63375] [4.8/4.9/5 Regression] reordering of reads across fences
Date: Fri, 26 Sep 2014 15:27:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc375

--- Comment #4 from Martin Jambor <jamborm at gcc dot gnu.org> ---
SRA is indeed quite guilty, the following patch fixes it:

diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index 8259dba..fb24114 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -1064,6 +1064,11 @@ build_access_from_expr_1 (tree expr, gimple stmt, bool
write)
                               "component.");
       return NULL;
     }
+  if (TREE_THIS_VOLATILE (expr))
+    {
+      disqualify_base_of_expr (expr, "part of a volatile reference.");
+      return NULL;
+    }

   switch (TREE_CODE (expr))
     {

Nevertheless, it is apparently not the only culprit.  Even on trunk
with -fno-tree-sra we produce exactly the same assembly output.  From
a brief look at the dumps it seems that RTL fwprop1 is the pass moving
the load, however I have not had a look if it is its fault or if
expansion looses the volatility information somehow.