So like this? I also added an assert that 'out' never exceeds 'len', > and
simplified the test
orig_arg
&& (PACK_EXPANSION_P (orig_arg) || ARGUMENT_PACK_P (orig_arg))
&& TREE_CODE (elts[i]) == TREE_VEC
to just
orig_arg
&& PACK_EXPANSION_P (orig_arg)
&& TREE_CODE (elts[i]) == TREE_VEC
since substitution into an ARGUMENT_PACK will never yield a TREE_VEC.
-- >8 --
Subject: [PATCH] c++: generic targs and identity substitution [PR105956]
PR c++/105956
gcc/cp/ChangeLog:
* pt.cc (tsubst_template_args): Move variable declarations
closer to their first use. Replace 'orig_t' with 'r'. Rename
'need_new' to 'const_subst_p'. Heuristically detect if the
substituted elements are identical to that of a level from
'args' and avoid allocating a new TREE_VEC if so. Assert that
'out' doesn't exceed 'len', and remove useless ARGUMENT_PACK_P
test.
(tsubst_decl) <case TYPE_DECL, case VAR_DECL>: Revert
r13-1045-gcb7fd1ea85feea change for avoiding substitution into
DECL_TI_ARGS, but still avoid coercion in this case.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/variadic183.C: New test.
---
gcc/cp/pt.cc | 128 +++++++++++++++--------
gcc/testsuite/g++.dg/cpp0x/variadic183.C | 14 +++
2 files changed, 99 insertions(+), 43 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/variadic183.C
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index 8672da123f4..c290174a390 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -27,6 +27,7 @@ along with GCC; see the file COPYING3. If not see
Fixed by: C++20 modules. */
#include "config.h"
+#define INCLUDE_ALGORITHM // for std::equal
#include "system.h"
#include "coretypes.h"
#include "cp-tree.h"
@@ -13544,17 +13545,22 @@ tsubst_argument_pack (tree orig_arg, tree args,
tsubst_flags_t complain,
tree
tsubst_template_args (tree t, tree args, tsubst_flags_t complain, tree
in_decl)
{
- tree orig_t = t;
- int len, need_new = 0, i, expanded_len_adjust = 0, out;
- tree *elts;
-
if (t == error_mark_node)
return error_mark_node;
- len = TREE_VEC_LENGTH (t);
- elts = XALLOCAVEC (tree, len);
+ const int len = TREE_VEC_LENGTH (t);
+ tree *elts = XALLOCAVEC (tree, len);
+ int expanded_len_adjust = 0;
- for (i = 0; i < len; i++)
+ /* True iff the substituted result is identical to T. */
+ bool const_subst_p = true;
+
+ /* If MAYBE_REUSE is a TREE_VEC, as an optimization we'll try to reuse and
+ return this TREE_VEC instead of allocating a new one if possible. This
+ will either be ARGS or a level from ARGS. */
+ tree maybe_reuse = NULL_TREE;
+
+ for (int i = 0; i < len; i++)
{
tree orig_arg = TREE_VEC_ELT (t, i);
tree new_arg;
@@ -13580,56 +13586,103 @@ tsubst_template_args (tree t, tree args,
tsubst_flags_t complain, tree in_decl)
else if (ARGUMENT_PACK_P (orig_arg))
new_arg = tsubst_argument_pack (orig_arg, args, complain, in_decl);
else
+ {
new_arg = tsubst_template_arg (orig_arg, args, complain, in_decl);
+ /* If T heuristically appears to be a set of generic template
+ arguments, set MAYBE_REUSE to the corresponding level from ARGS.
+ Otherwise set it to error_mark_node. (Note that this doesn't
+ handle variadic template parameters, which are represented as a
+ generic arg by an ARGUMENT_PACK around a one-element TREE_VEC
+ containing a PACK_EXPANSION. We partially handle that case
+ later.) */
+ if (maybe_reuse == NULL_TREE && orig_arg != NULL_TREE)
+ {
+ if (TEMPLATE_PARM_P (orig_arg))
+ {
+ int level, index;
+ template_parm_level_and_index (orig_arg, &level, &index);
+ if (index == i && TMPL_ARGS_DEPTH (args) >= level)
+ maybe_reuse = TMPL_ARGS_LEVEL (args, level);
+ else
+ maybe_reuse = error_mark_node;
+ }
+ else
+ maybe_reuse = error_mark_node;
+ }
+ }
+
if (new_arg == error_mark_node)
return error_mark_node;
elts[i] = new_arg;
if (new_arg != orig_arg)
- need_new = 1;
+ const_subst_p = false;
}
- if (!need_new)
+ if (const_subst_p)
return t;
+ /* If ARGS and T are both multi-level, the substituted result may be
+ identical to ARGS (if each level was pairwise identical). */
+ if (maybe_reuse == NULL_TREE
+ && TMPL_ARGS_HAVE_MULTIPLE_LEVELS (t)
+ && TMPL_ARGS_HAVE_MULTIPLE_LEVELS (args))
+ maybe_reuse = args;
+
+ /* Return MAYBE_REUSE and avoid allocating a new TREE_VEC if the substituted
+ result is identical to it. */
+ if (NON_ERROR (maybe_reuse) != NULL_TREE
+ && TREE_VEC_LENGTH (maybe_reuse) == len
+ && std::equal (elts, elts+len, TREE_VEC_BEGIN (maybe_reuse)))
+ return maybe_reuse;
+
+ /* If T consists of only a pack expansion for which substitution resulted
+ in a TREE_VEC of the expanded elements, then reuse that TREE_VEC instead
+ of effectively making a copy. */
+ if (len == 1
+ && PACK_EXPANSION_P (TREE_VEC_ELT (t, 0))
+ && TREE_CODE (elts[0]) == TREE_VEC)
+ return elts[0];
+
/* Make space for the expanded arguments coming from template
argument packs. */
- t = make_tree_vec (len + expanded_len_adjust);
- /* ORIG_T can contain TREE_VECs. That happens if ORIG_T contains the
+ tree r = make_tree_vec (len + expanded_len_adjust);
+ /* T can contain TREE_VECs. That happens if T contains the
arguments for a member template.
- In that case each TREE_VEC in ORIG_T represents a level of template
- arguments, and ORIG_T won't carry any non defaulted argument count.
+ In that case each TREE_VEC in T represents a level of template
+ arguments, and T won't carry any non defaulted argument count.
It will rather be the nested TREE_VECs that will carry one.
- In other words, ORIG_T carries a non defaulted argument count only
+ In other words, T carries a non defaulted argument count only
if it doesn't contain any nested TREE_VEC. */
- if (NON_DEFAULT_TEMPLATE_ARGS_COUNT (orig_t))
+ if (NON_DEFAULT_TEMPLATE_ARGS_COUNT (t))
{
- int count = GET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (orig_t);
+ int count = GET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (t);
count += expanded_len_adjust;
- SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (t, count);
+ SET_NON_DEFAULT_TEMPLATE_ARGS_COUNT (r, count);
}
- for (i = 0, out = 0; i < len; i++)
+
+ int out = 0;
+ for (int i = 0; i < len; i++)
{
- tree orig_arg = TREE_VEC_ELT (orig_t, i);
+ tree orig_arg = TREE_VEC_ELT (t, i);
if (orig_arg
- && (PACK_EXPANSION_P (orig_arg) || ARGUMENT_PACK_P (orig_arg))
+ && PACK_EXPANSION_P (orig_arg)
&& TREE_CODE (elts[i]) == TREE_VEC)
{
- int idx;
-
/* Now expand the template argument pack "in place". */
- for (idx = 0; idx < TREE_VEC_LENGTH (elts[i]); idx++, out++)
- TREE_VEC_ELT (t, out) = TREE_VEC_ELT (elts[i], idx);
+ for (int idx = 0; idx < TREE_VEC_LENGTH (elts[i]); idx++, out++)
+ TREE_VEC_ELT (r, out) = TREE_VEC_ELT (elts[i], idx);
}
else
{
- TREE_VEC_ELT (t, out) = elts[i];
+ TREE_VEC_ELT (r, out) = elts[i];
out++;
}
}
+ gcc_assert (out <= TREE_VEC_LENGTH (r));
- return t;
+ return r;
}
/* Substitute ARGS into one level PARMS of template parameters. */
@@ -14965,32 +15018,21 @@ tsubst_decl (tree t, tree args, tsubst_flags_t
complain)
if (!spec)
{
- int args_depth = TMPL_ARGS_DEPTH (args);
- int parms_depth = TMPL_ARGS_DEPTH (DECL_TI_ARGS (t));
tmpl = DECL_TI_TEMPLATE (t);
gen_tmpl = most_general_template (tmpl);
- if (args_depth == parms_depth
- && !PRIMARY_TEMPLATE_P (gen_tmpl))
- /* The DECL_TI_ARGS in this case are the generic template
- arguments for the enclosing class template, so we can
- shortcut substitution (which would just be the identity
- mapping). */
- argvec = args;
- else
- {
argvec = tsubst (DECL_TI_ARGS (t), args, complain, in_decl);
- /* Coerce the innermost arguments again if necessary. If
- there's fewer levels of args than of parms, then the
- substitution could not have changed the innermost args
- (modulo level lowering). */
- if (args_depth >= parms_depth && argvec != error_mark_node)
+ if (argvec != error_mark_node
+ && PRIMARY_TEMPLATE_P (gen_tmpl)
+ && TMPL_ARGS_DEPTH (args) >= TMPL_ARGS_DEPTH (argvec))
+ /* We're fully specializing a template declaration, so
+ we need to coerce the innermost arguments corresponding to
+ the template. */
argvec = (coerce_innermost_template_parms
(DECL_TEMPLATE_PARMS (gen_tmpl),
argvec, t, complain,
/*all*/true, /*defarg*/true));
if (argvec == error_mark_node)
RETURN (error_mark_node);
- }
hash = spec_hasher::hash (gen_tmpl, argvec);
spec = retrieve_specialization (gen_tmpl, argvec, hash);
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic183.C
b/gcc/testsuite/g++.dg/cpp0x/variadic183.C
new file mode 100644
index 00000000000..27444ebb594
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic183.C
@@ -0,0 +1,14 @@
+// PR c++/105956
+// { dg-do compile { target c++11 } }
+
+template<int...> struct list;
+
+template<int... Ns> struct impl {
+ static const int idx = 0;
+ using type = list<(idx + Ns)...>;
+
+ static constexpr const int* a[2] = {(Ns, &idx)...};
+ static_assert(a[0] == &idx && a[1] == &idx, "");
+};
+
+template struct impl<0, 1>;
