r326973 - When substituting previously-checked template arguments into a template
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Wed Mar 7 17:07:33 PST 2018
Author: rsmith
Date: Wed Mar 7 17:07:33 2018
New Revision: 326973
URL: http://llvm.org/viewvc/llvm-project?rev=326973&view=rev
Log:
When substituting previously-checked template arguments into a template
template parameter that is an expanded parameter pack, only substitute into the
current slice, not the entire pack.
This reduces the checking of N template template arguments for an expanded
parameter pack containing N parameters from quadratic time to linear time in
the length of the pack. This is important because one (and possibly the only?)
general technique for splitting a template parameter pack in linear time
depends on doing this.
Added:
cfe/trunk/test/SemaTemplate/temp-param-subst-linear.cpp
Modified:
cfe/trunk/include/clang/Sema/Sema.h
cfe/trunk/lib/Sema/SemaTemplate.cpp
cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
cfe/trunk/test/CXX/drs/dr10xx.cpp
Modified: cfe/trunk/include/clang/Sema/Sema.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Sema/Sema.h?rev=326973&r1=326972&r2=326973&view=diff
==============================================================================
--- cfe/trunk/include/clang/Sema/Sema.h (original)
+++ cfe/trunk/include/clang/Sema/Sema.h Wed Mar 7 17:07:33 2018
@@ -6362,9 +6362,8 @@ public:
QualType InstantiatedParamType, Expr *Arg,
TemplateArgument &Converted,
CheckTemplateArgumentKind CTAK = CTAK_Specified);
- bool CheckTemplateArgument(TemplateTemplateParmDecl *Param,
- TemplateArgumentLoc &Arg,
- unsigned ArgumentPackIndex);
+ bool CheckTemplateTemplateArgument(TemplateParameterList *Params,
+ TemplateArgumentLoc &Arg);
ExprResult
BuildExpressionFromDeclTemplateArgument(const TemplateArgument &Arg,
@@ -7700,6 +7699,10 @@ public:
StmtResult SubstStmt(Stmt *S,
const MultiLevelTemplateArgumentList &TemplateArgs);
+ TemplateParameterList *
+ SubstTemplateParams(TemplateParameterList *Params, DeclContext *Owner,
+ const MultiLevelTemplateArgumentList &TemplateArgs);
+
Decl *SubstDecl(Decl *D, DeclContext *Owner,
const MultiLevelTemplateArgumentList &TemplateArgs);
Modified: cfe/trunk/lib/Sema/SemaTemplate.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplate.cpp?rev=326973&r1=326972&r2=326973&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplate.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplate.cpp Wed Mar 7 17:07:33 2018
@@ -4617,6 +4617,8 @@ bool Sema::CheckTemplateArgument(NamedDe
if (NTTP->isParameterPack() && NTTP->isExpandedParameterPack())
NTTPType = NTTP->getExpansionType(ArgumentPackIndex);
+ // FIXME: Do we need to substitute into parameters here if they're
+ // instantiation-dependent but not dependent?
if (NTTPType->isDependentType() &&
!isa<TemplateTemplateParmDecl>(Template) &&
!Template->getDeclContext()->isDependentContext()) {
@@ -4756,9 +4758,15 @@ bool Sema::CheckTemplateArgument(NamedDe
// Check template template parameters.
TemplateTemplateParmDecl *TempParm = cast<TemplateTemplateParmDecl>(Param);
+ TemplateParameterList *Params = TempParm->getTemplateParameters();
+ if (TempParm->isExpandedParameterPack())
+ Params = TempParm->getExpansionTemplateParameters(ArgumentPackIndex);
+
// Substitute into the template parameter list of the template
// template parameter, since previously-supplied template arguments
// may appear within the template template parameter.
+ //
+ // FIXME: Skip this if the parameters aren't instantiation-dependent.
{
// Set up a template instantiation context.
LocalInstantiationScope Scope(*this);
@@ -4769,10 +4777,9 @@ bool Sema::CheckTemplateArgument(NamedDe
return true;
TemplateArgumentList TemplateArgs(TemplateArgumentList::OnStack, Converted);
- TempParm = cast_or_null<TemplateTemplateParmDecl>(
- SubstDecl(TempParm, CurContext,
- MultiLevelTemplateArgumentList(TemplateArgs)));
- if (!TempParm)
+ Params = SubstTemplateParams(Params, CurContext,
+ MultiLevelTemplateArgumentList(TemplateArgs));
+ if (!Params)
return true;
}
@@ -4793,7 +4800,7 @@ bool Sema::CheckTemplateArgument(NamedDe
case TemplateArgument::Template:
case TemplateArgument::TemplateExpansion:
- if (CheckTemplateArgument(TempParm, Arg, ArgumentPackIndex))
+ if (CheckTemplateTemplateArgument(Params, Arg))
return true;
Converted.push_back(Arg.getArgument());
@@ -6536,9 +6543,8 @@ static void DiagnoseTemplateParameterLis
///
/// This routine implements the semantics of C++ [temp.arg.template].
/// It returns true if an error occurred, and false otherwise.
-bool Sema::CheckTemplateArgument(TemplateTemplateParmDecl *Param,
- TemplateArgumentLoc &Arg,
- unsigned ArgumentPackIndex) {
+bool Sema::CheckTemplateTemplateArgument(TemplateParameterList *Params,
+ TemplateArgumentLoc &Arg) {
TemplateName Name = Arg.getArgument().getAsTemplateOrTemplatePattern();
TemplateDecl *Template = Name.getAsTemplateDecl();
if (!Template) {
@@ -6573,10 +6579,6 @@ bool Sema::CheckTemplateArgument(Templat
<< Template;
}
- TemplateParameterList *Params = Param->getTemplateParameters();
- if (Param->isExpandedParameterPack())
- Params = Param->getExpansionTemplateParameters(ArgumentPackIndex);
-
// C++1z [temp.arg.template]p3: (DR 150)
// A template-argument matches a template template-parameter P when P
// is at least as specialized as the template-argument A.
Modified: cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp?rev=326973&r1=326972&r2=326973&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp Wed Mar 7 17:07:33 2018
@@ -3118,6 +3118,13 @@ TemplateDeclInstantiator::SubstTemplateP
return InstL;
}
+TemplateParameterList *
+Sema::SubstTemplateParams(TemplateParameterList *Params, DeclContext *Owner,
+ const MultiLevelTemplateArgumentList &TemplateArgs) {
+ TemplateDeclInstantiator Instantiator(*this, Owner, TemplateArgs);
+ return Instantiator.SubstTemplateParams(Params);
+}
+
/// \brief Instantiate the declaration of a class template partial
/// specialization.
///
Modified: cfe/trunk/test/CXX/drs/dr10xx.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr10xx.cpp?rev=326973&r1=326972&r2=326973&view=diff
==============================================================================
--- cfe/trunk/test/CXX/drs/dr10xx.cpp (original)
+++ cfe/trunk/test/CXX/drs/dr10xx.cpp Wed Mar 7 17:07:33 2018
@@ -31,9 +31,8 @@ namespace dr1004 { // dr1004: 5
// This example (from the standard) is actually ill-formed, because
// name lookup of "T::template A" names the constructor.
- // FIXME: Only issue one diagnostic for this case.
- template<class T, template<class> class U = T::template A> struct Third { }; // expected-error 2{{is a constructor name}}
- Third<A<int> > t; // expected-note {{in instantiation of}} expected-note {{while substituting}} expected-note {{while checking}}
+ template<class T, template<class> class U = T::template A> struct Third { }; // expected-error {{is a constructor name}}
+ Third<A<int> > t; // expected-note {{in instantiation of default argument}}
}
namespace dr1048 { // dr1048: 3.6
Added: cfe/trunk/test/SemaTemplate/temp-param-subst-linear.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaTemplate/temp-param-subst-linear.cpp?rev=326973&view=auto
==============================================================================
--- cfe/trunk/test/SemaTemplate/temp-param-subst-linear.cpp (added)
+++ cfe/trunk/test/SemaTemplate/temp-param-subst-linear.cpp Wed Mar 7 17:07:33 2018
@@ -0,0 +1,56 @@
+// RUN: %clang_cc1 -std=c++17 %s -verify
+// expected-no-diagnostics
+
+// This test attempts to ensure that the below template parameter pack
+// splitting technique executes in linear time in the number of template
+// parameters. The size of the list below is selected so as to execute
+// relatively quickly on a "good" compiler and to time out otherwise.
+
+template<typename...> struct TypeList;
+
+namespace detail {
+template<unsigned> using Unsigned = unsigned;
+template<typename T, T ...N> using ListOfNUnsignedsImpl = TypeList<Unsigned<N>...>;
+template<unsigned N> using ListOfNUnsigneds =
+ __make_integer_seq<ListOfNUnsignedsImpl, unsigned, N>;
+
+template<typename T> struct TypeWrapper {
+ template<unsigned> using AsTemplate = T;
+};
+
+template<typename ...N> struct Splitter {
+ template<template<N> class ...L,
+ template<unsigned> class ...R> struct Split {
+ using Left = TypeList<L<0>...>;
+ using Right = TypeList<R<0>...>;
+ };
+};
+}
+
+template<typename TypeList, unsigned N, typename = detail::ListOfNUnsigneds<N>>
+struct SplitAtIndex;
+
+template<typename ...T, unsigned N, typename ...NUnsigneds>
+struct SplitAtIndex<TypeList<T...>, N, TypeList<NUnsigneds...>> :
+ detail::Splitter<NUnsigneds...>::
+ template Split<detail::TypeWrapper<T>::template AsTemplate...> {};
+
+template<typename T, int N> struct Rep : Rep<typename Rep<T, N-1>::type, 1> {};
+template<typename ...T> struct Rep<TypeList<T...>, 1> { typedef TypeList<T..., T...> type; };
+
+using Ints = Rep<TypeList<int>, 14>::type;
+
+template<typename T> extern int Size;
+template<typename ...T> constexpr int Size<TypeList<T...>> = sizeof...(T);
+
+using Left = SplitAtIndex<Ints, Size<Ints> / 2>::Left;
+using Right = SplitAtIndex<Ints, Size<Ints> / 2>::Right;
+static_assert(Size<Left> == 8192);
+static_assert(Size<Right> == 8192);
+
+template<typename L, typename R> struct Concat;
+template<typename ...L, typename ...R> struct Concat<TypeList<L...>, TypeList<R...>> {
+ using type = TypeList<L..., R...>;
+};
+
+using Ints = Concat<Left, Right>::type;
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