From 094091958654bae07a9ad53a63fd69468efcd3e3 Mon Sep 17 00:00:00 2001
From: Patrick Palka <ppalka@redhat.com>
Date: Mon, 18 Sep 2023 14:27:18 -0400
Subject: [PATCH] c++: optimize tsubst_template_decl for function templates
r14-2655-g92d1425ca78040 made instantiate_template avoid redundantly
performing a specialization lookup when calling tsubst_decl. This patch
applies the same optimization to the analagous tsubst_template_decl when
(partially) instantiating a function template. This allows us to remove
an early exit test from register_specialization since we no longer try
to register the FUNCTION_DECL corresponding to a function template
partial instantiation.
gcc/cp/ChangeLog:
* pt.cc (register_specialization): Remove now-unnecessary
early exit for FUNCTION_DECL partial instantiation.
(tsubst_template_decl): Pass use_spec_table=false to
tsubst_function_decl. Set DECL_TI_ARGS of a non-lambda
FUNCTION_DECL specialization to the full set of arguments.
Simplify register_specialization call accordingly.
gcc/testsuite/ChangeLog:
* g++.dg/template/nontype12.C: Expect two instead of three
duplicate diagnostics for A<double>::bar() specialization.
---
gcc/cp/pt.cc | 29 +++++++----------------
gcc/testsuite/g++.dg/template/nontype12.C | 3 ++-
2 files changed, 11 insertions(+), 21 deletions(-)
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index b583c11eb995..a40b8953e629 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -1507,21 +1507,6 @@ register_specialization (tree spec, tree tmpl, tree args, bool is_friend,
|| (TREE_CODE (tmpl) == FIELD_DECL
&& TREE_CODE (spec) == NONTYPE_ARGUMENT_PACK));
- if (TREE_CODE (spec) == FUNCTION_DECL
- && uses_template_parms (DECL_TI_ARGS (spec)))
- /* This is the FUNCTION_DECL for a partial instantiation. Don't
- register it; we want the corresponding TEMPLATE_DECL instead.
- We use `uses_template_parms (DECL_TI_ARGS (spec))' rather than
- the more obvious `uses_template_parms (spec)' to avoid problems
- with default function arguments. In particular, given
- something like this:
-
- template <class T> void f(T t1, T t = T())
-
- the default argument expression is not substituted for in an
- instantiation unless and until it is actually needed. */
- return spec;
-
spec_entry elt;
elt.tmpl = tmpl;
elt.args = args;
@@ -14665,7 +14650,7 @@ tsubst_template_decl (tree t, tree args, tsubst_flags_t complain,
tree in_decl = t;
tree spec;
tree tmpl_args;
- tree full_args;
+ tree full_args = NULL_TREE;
tree r;
hashval_t hash = 0;
@@ -14756,7 +14741,8 @@ tsubst_template_decl (tree t, tree args, tsubst_flags_t complain,
tree inner = decl;
++processing_template_decl;
if (TREE_CODE (inner) == FUNCTION_DECL)
- inner = tsubst_function_decl (inner, args, complain, lambda_fntype);
+ inner = tsubst_function_decl (inner, args, complain, lambda_fntype,
+ /*use_spec_table=*/false);
else
{
if (TREE_CODE (inner) == TYPE_DECL && !TYPE_DECL_ALIAS_P (inner))
@@ -14794,6 +14780,11 @@ tsubst_template_decl (tree t, tree args, tsubst_flags_t complain,
}
else
{
+ if (TREE_CODE (inner) == FUNCTION_DECL)
+ /* Set DECL_TI_ARGS to the full set of template arguments, which
+ tsubst_function_decl didn't do due to use_spec_table=false. */
+ DECL_TI_ARGS (inner) = full_args;
+
DECL_TI_TEMPLATE (inner) = r;
DECL_TI_ARGS (r) = DECL_TI_ARGS (inner);
}
@@ -14824,9 +14815,7 @@ tsubst_template_decl (tree t, tree args, tsubst_flags_t complain,
if (TREE_CODE (decl) == FUNCTION_DECL && !lambda_fntype)
/* Record this non-type partial instantiation. */
- register_specialization (r, t,
- DECL_TI_ARGS (DECL_TEMPLATE_RESULT (r)),
- false, hash);
+ register_specialization (r, t, full_args, false, hash);
return r;
}
diff --git a/gcc/testsuite/g++.dg/template/nontype12.C b/gcc/testsuite/g++.dg/template/nontype12.C
index 9a9c3ac1e662..a0e701818629 100644
--- a/gcc/testsuite/g++.dg/template/nontype12.C
+++ b/gcc/testsuite/g++.dg/template/nontype12.C
@@ -5,7 +5,8 @@ template<typename T> struct A
{
template<T> int foo(); // { dg-error "double" "" { target c++17_down } }
template<template<T> class> int bar(); // { dg-bogus {double[^\n]*\n[^\n]*C:7:[^\n]*double} "" { xfail c++17_down } }
- // { dg-error "double" "" { target c++17_down } .-1 }
+ // The above xfailed dg-bogus test means that we issue two errors
+ // for the invalid 'double' NTTP, and preferably we'd issue just one.
template<T> struct X; // { dg-error "double" "" { target c++17_down } }
};
--
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