When substituting a class template specialization, tsubst_aggr_type substitutes the TYPE_CONTEXT before passing it to lookup_template_class. This appears to be unnecessary, however, because the the initial value of lookup_template_class's context parameter is unused outside of the IDENTIFIER_NODE case, and l_t_c performs its own substitution of the context, anyway. So this patch removes the redundant substitution in tsubst_aggr_type. Doing so causes us to ICE on template/nested5.C because during lookup_template_class for A<T>::C::D<S> with T=E and S=S, we substitute and complete the context A<T>::C with T=E, which in turn registers the desired dependent specialization of D for us and we end up trying to register it again. This patch fixes this by checking the specializations table again after completion of the context.
This patch also implements a couple of other optimizations: * In lookup_template_class, if the context of the partially instantiated template is already non-dependent, then we could reuse that instead of substituting the context of the most general template. * When substituting the TYPE_DECL for an injected-class-name in tsubst_decl, we can avoid substituting its TREE_TYPE and DECL_TI_ARGS. Together these optimizations improve memory usage for the range-v3 testcase test/view/split.cc by about 5%. The improvement is probably more significant when dealing with deeply nested class templates. Bootstrapped and regtested on x86_64-pc-linux-gnu, does this look OK for trunk? gcc/cp/ChangeLog: * pt.cc (lookup_template_class): Remove dead stores to context parameter. Don't substitute the context of the most general template if that of the partially instantiated template is non-dependent. Check the specializations table again after completing the context of a nested dependent specialization. (tsubst_aggr_type) <case RECORD_TYPE>: Don't substitute TYPE_CONTEXT or pass it to lookup_template_class. (tsubst_decl) <case TYPE_DECL>: Avoid substituting the TREE_TYPE and DECL_TI_ARGS when DECL_SELF_REFERENCE_P. --- gcc/cp/pt.cc | 69 +++++++++++++++++++++++++++++++--------------------- 1 file changed, 41 insertions(+), 28 deletions(-) diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc index 59b94317e88..28023d60684 100644 --- a/gcc/cp/pt.cc +++ b/gcc/cp/pt.cc @@ -9840,8 +9840,6 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context, if (context) pop_decl_namespace (); } - if (templ) - context = DECL_CONTEXT (templ); } else if (TREE_CODE (d1) == TYPE_DECL && MAYBE_CLASS_TYPE_P (TREE_TYPE (d1))) { @@ -9868,7 +9866,6 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context, { templ = d1; d1 = DECL_NAME (templ); - context = DECL_CONTEXT (templ); } else if (DECL_TEMPLATE_TEMPLATE_PARM_P (d1)) { @@ -10059,8 +10056,25 @@ lookup_template_class (tree d1, tree arglist, tree in_decl, tree context, context = DECL_CONTEXT (gen_tmpl); if (context && TYPE_P (context)) { - context = tsubst_aggr_type (context, arglist, complain, in_decl, true); - context = complete_type (context); + if (!uses_template_parms (DECL_CONTEXT (templ))) + /* If the context of the partially instantiated template is + already non-dependent, then we might as well use it. */ + context = DECL_CONTEXT (templ); + else + { + context = tsubst_aggr_type (context, arglist, complain, in_decl, true); + context = complete_type (context); + if (is_dependent_type && arg_depth > 1) + { + /* If this is a dependent nested specialization such as + A<int>::B<T>, then completion of A<int> might have + registered this specialization of B for us, so check + the table again (33959). */ + entry = type_specializations->find_with_hash (&elt, hash); + if (entry) + return entry->spec; + } + } } else context = tsubst (context, arglist, complain, in_decl); @@ -13711,25 +13725,12 @@ tsubst_aggr_type (tree t, if (TYPE_TEMPLATE_INFO (t) && uses_template_parms (t)) { tree argvec; - tree context; tree r; /* In "sizeof(X<I>)" we need to evaluate "I". */ cp_evaluated ev; - /* First, determine the context for the type we are looking - up. */ - context = TYPE_CONTEXT (t); - if (context && TYPE_P (context)) - { - context = tsubst_aggr_type (context, args, complain, - in_decl, /*entering_scope=*/1); - /* If context is a nested class inside a class template, - it may still need to be instantiated (c++/33959). */ - context = complete_type (context); - } - - /* Then, figure out what arguments are appropriate for the + /* Figure out what arguments are appropriate for the type we are trying to find. For example, given: template <class T> struct S; @@ -13744,7 +13745,7 @@ tsubst_aggr_type (tree t, r = error_mark_node; else { - r = lookup_template_class (t, argvec, in_decl, context, + r = lookup_template_class (t, argvec, in_decl, NULL_TREE, entering_scope, complain); r = cp_build_qualified_type (r, cp_type_quals (t), complain); } @@ -14880,6 +14881,10 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain) ctx = tsubst_aggr_type (ctx, args, complain, in_decl, /*entering_scope=*/1); + if (DECL_SELF_REFERENCE_P (t)) + /* The context and type of a injected-class-name are + the same, so we don't need to substitute both. */ + type = ctx; /* If CTX is unchanged, then T is in fact the specialization we want. That situation occurs when referencing a static data member within in its own @@ -14900,14 +14905,22 @@ tsubst_decl (tree t, tree args, tsubst_flags_t complain) { tmpl = DECL_TI_TEMPLATE (t); gen_tmpl = most_general_template (tmpl); - argvec = tsubst (DECL_TI_ARGS (t), args, complain, in_decl); - if (argvec != error_mark_node) - 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); + if (DECL_SELF_REFERENCE_P (t)) + /* The DECL_TI_ARGS for the injected-class-name are the + generic template arguments for the class template, so + substitution/coercion is just the identity mapping. */ + argvec = args; + else + { + argvec = tsubst (DECL_TI_ARGS (t), args, complain, in_decl); + if (argvec != error_mark_node) + 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 = hash_tmpl_and_args (gen_tmpl, argvec); spec = retrieve_specialization (gen_tmpl, argvec, hash); } -- 2.36.1.363.g9c897eef06