[clang] [Clang] Don't give up on an unsuccessful function instantiation (PR #126723)
Younan Zhang via cfe-commits
cfe-commits at lists.llvm.org
Tue Feb 11 17:47:06 PST 2025
https://github.com/zyn0217 updated https://github.com/llvm/llvm-project/pull/126723
>From 21ca76a13ca62715ce98fb2c8b0361df727769b0 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Tue, 11 Feb 2025 17:13:34 +0800
Subject: [PATCH 1/2] [Clang] Don't give up on an unsuccessful function
instantiation
For constexpr function templates, we immediately instantiate them
upon reference. However, if the function isn't defined at the
point of instantiation, even though it might be defined later,
the instantiation would simply fail.
This patch corrects the behavior by popping up failed instantiations
through PendingInstantiations, so that we are able to instantiate
them again in the future (e.g. at the end of TU.)
---
clang/include/clang/Sema/Sema.h | 23 ++++++---
clang/lib/Interpreter/IncrementalParser.cpp | 5 +-
.../lib/Sema/SemaTemplateInstantiateDecl.cpp | 47 ++++++++++++-------
.../function-template-specialization.cpp | 19 +++++++-
4 files changed, 67 insertions(+), 27 deletions(-)
diff --git a/clang/include/clang/Sema/Sema.h b/clang/include/clang/Sema/Sema.h
index 472a0e25adc97..2083a2c2ca40d 100644
--- a/clang/include/clang/Sema/Sema.h
+++ b/clang/include/clang/Sema/Sema.h
@@ -13588,12 +13588,16 @@ class Sema final : public SemaBase {
class LocalEagerInstantiationScope {
public:
- LocalEagerInstantiationScope(Sema &S) : S(S) {
+ LocalEagerInstantiationScope(Sema &S, bool AtEndOfTU)
+ : S(S), AtEndOfTU(AtEndOfTU) {
SavedPendingLocalImplicitInstantiations.swap(
S.PendingLocalImplicitInstantiations);
}
- void perform() { S.PerformPendingInstantiations(/*LocalOnly=*/true); }
+ void perform() {
+ S.PerformPendingInstantiations(/*LocalOnly=*/true,
+ /*AtEndOfTU=*/AtEndOfTU);
+ }
~LocalEagerInstantiationScope() {
assert(S.PendingLocalImplicitInstantiations.empty() &&
@@ -13604,6 +13608,7 @@ class Sema final : public SemaBase {
private:
Sema &S;
+ bool AtEndOfTU;
std::deque<PendingImplicitInstantiation>
SavedPendingLocalImplicitInstantiations;
};
@@ -13626,8 +13631,8 @@ class Sema final : public SemaBase {
class GlobalEagerInstantiationScope {
public:
- GlobalEagerInstantiationScope(Sema &S, bool Enabled)
- : S(S), Enabled(Enabled) {
+ GlobalEagerInstantiationScope(Sema &S, bool Enabled, bool AtEndOfTU)
+ : S(S), Enabled(Enabled), AtEndOfTU(AtEndOfTU) {
if (!Enabled)
return;
@@ -13641,7 +13646,8 @@ class Sema final : public SemaBase {
void perform() {
if (Enabled) {
S.DefineUsedVTables();
- S.PerformPendingInstantiations();
+ S.PerformPendingInstantiations(/*LocalOnly=*/false,
+ /*AtEndOfTU=*/AtEndOfTU);
}
}
@@ -13656,7 +13662,8 @@ class Sema final : public SemaBase {
S.SavedVTableUses.pop_back();
// Restore the set of pending implicit instantiations.
- if (S.TUKind != TU_Prefix || !S.LangOpts.PCHInstantiateTemplates) {
+ if ((S.TUKind != TU_Prefix || !S.LangOpts.PCHInstantiateTemplates) &&
+ AtEndOfTU) {
assert(S.PendingInstantiations.empty() &&
"PendingInstantiations should be empty before it is discarded.");
S.PendingInstantiations.swap(S.SavedPendingInstantiations.back());
@@ -13675,6 +13682,7 @@ class Sema final : public SemaBase {
private:
Sema &S;
bool Enabled;
+ bool AtEndOfTU;
};
ExplicitSpecifier instantiateExplicitSpecifier(
@@ -13860,7 +13868,8 @@ class Sema final : public SemaBase {
/// Performs template instantiation for all implicit template
/// instantiations we have seen until this point.
- void PerformPendingInstantiations(bool LocalOnly = false);
+ void PerformPendingInstantiations(bool LocalOnly = false,
+ bool AtEndOfTU = true);
TemplateParameterList *
SubstTemplateParams(TemplateParameterList *Params, DeclContext *Owner,
diff --git a/clang/lib/Interpreter/IncrementalParser.cpp b/clang/lib/Interpreter/IncrementalParser.cpp
index e43cea1baf43a..41d6304bd5f65 100644
--- a/clang/lib/Interpreter/IncrementalParser.cpp
+++ b/clang/lib/Interpreter/IncrementalParser.cpp
@@ -41,8 +41,9 @@ llvm::Expected<TranslationUnitDecl *>
IncrementalParser::ParseOrWrapTopLevelDecl() {
// Recover resources if we crash before exiting this method.
llvm::CrashRecoveryContextCleanupRegistrar<Sema> CleanupSema(&S);
- Sema::GlobalEagerInstantiationScope GlobalInstantiations(S, /*Enabled=*/true);
- Sema::LocalEagerInstantiationScope LocalInstantiations(S);
+ Sema::GlobalEagerInstantiationScope GlobalInstantiations(S, /*Enabled=*/true,
+ /*AtEndOfTU=*/true);
+ Sema::LocalEagerInstantiationScope LocalInstantiations(S, /*AtEndOfTU=*/true);
// Add a new PTU.
ASTContext &C = S.getASTContext();
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index d530ed0847ae8..13d157e2a48d1 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -2139,7 +2139,8 @@ Decl *TemplateDeclInstantiator::VisitCXXRecordDecl(CXXRecordDecl *D) {
// DR1484 clarifies that the members of a local class are instantiated as part
// of the instantiation of their enclosing entity.
if (D->isCompleteDefinition() && D->isLocalClass()) {
- Sema::LocalEagerInstantiationScope LocalInstantiations(SemaRef);
+ Sema::LocalEagerInstantiationScope LocalInstantiations(SemaRef,
+ /*AtEndOfTU=*/false);
SemaRef.InstantiateClass(D->getLocation(), Record, D, TemplateArgs,
TSK_ImplicitInstantiation,
@@ -5121,8 +5122,10 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
// This has to happen before LateTemplateParser below is called, so that
// it marks vtables used in late parsed templates as used.
GlobalEagerInstantiationScope GlobalInstantiations(*this,
- /*Enabled=*/Recursive);
- LocalEagerInstantiationScope LocalInstantiations(*this);
+ /*Enabled=*/Recursive,
+ /*AtEndOfTU=*/AtEndOfTU);
+ LocalEagerInstantiationScope LocalInstantiations(*this,
+ /*AtEndOfTU=*/AtEndOfTU);
// Call the LateTemplateParser callback if there is a need to late parse
// a templated function definition.
@@ -5691,10 +5694,12 @@ void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
// If we're performing recursive template instantiation, create our own
// queue of pending implicit instantiations that we will instantiate
// later, while we're still within our own instantiation context.
- GlobalEagerInstantiationScope GlobalInstantiations(*this,
- /*Enabled=*/Recursive);
+ GlobalEagerInstantiationScope GlobalInstantiations(
+ *this,
+ /*Enabled=*/Recursive, /*AtEndOfTU=*/AtEndOfTU);
LocalInstantiationScope Local(*this);
- LocalEagerInstantiationScope LocalInstantiations(*this);
+ LocalEagerInstantiationScope LocalInstantiations(*this,
+ /*AtEndOfTU=*/AtEndOfTU);
// Enter the scope of this instantiation. We don't use
// PushDeclContext because we don't have a scope.
@@ -5791,14 +5796,16 @@ void Sema::InstantiateVariableDefinition(SourceLocation PointOfInstantiation,
// queue of pending implicit instantiations that we will instantiate later,
// while we're still within our own instantiation context.
GlobalEagerInstantiationScope GlobalInstantiations(*this,
- /*Enabled=*/Recursive);
+ /*Enabled=*/Recursive,
+ /*AtEndOfTU=*/AtEndOfTU);
// Enter the scope of this instantiation. We don't use
// PushDeclContext because we don't have a scope.
ContextRAII PreviousContext(*this, Var->getDeclContext());
LocalInstantiationScope Local(*this);
- LocalEagerInstantiationScope LocalInstantiations(*this);
+ LocalEagerInstantiationScope LocalInstantiations(*this,
+ /*AtEndOfTU=*/AtEndOfTU);
VarDecl *OldVar = Var;
if (Def->isStaticDataMember() && !Def->isOutOfLine()) {
@@ -6548,18 +6555,20 @@ NamedDecl *Sema::FindInstantiatedDecl(SourceLocation Loc, NamedDecl *D,
return D;
}
-void Sema::PerformPendingInstantiations(bool LocalOnly) {
- std::deque<PendingImplicitInstantiation> delayedPCHInstantiations;
+void Sema::PerformPendingInstantiations(bool LocalOnly, bool AtEndOfTU) {
+ std::deque<PendingImplicitInstantiation> DelayedImplicitInstantiations;
while (!PendingLocalImplicitInstantiations.empty() ||
(!LocalOnly && !PendingInstantiations.empty())) {
PendingImplicitInstantiation Inst;
+ bool LocalInstantiation = false;
if (PendingLocalImplicitInstantiations.empty()) {
Inst = PendingInstantiations.front();
PendingInstantiations.pop_front();
} else {
Inst = PendingLocalImplicitInstantiations.front();
PendingLocalImplicitInstantiations.pop_front();
+ LocalInstantiation = true;
}
// Instantiate function definitions
@@ -6568,22 +6577,26 @@ void Sema::PerformPendingInstantiations(bool LocalOnly) {
TSK_ExplicitInstantiationDefinition;
if (Function->isMultiVersion()) {
getASTContext().forEachMultiversionedFunctionVersion(
- Function, [this, Inst, DefinitionRequired](FunctionDecl *CurFD) {
+ Function,
+ [this, Inst, DefinitionRequired, AtEndOfTU](FunctionDecl *CurFD) {
InstantiateFunctionDefinition(/*FIXME:*/ Inst.second, CurFD, true,
- DefinitionRequired, true);
+ DefinitionRequired, AtEndOfTU);
if (CurFD->isDefined())
CurFD->setInstantiationIsPending(false);
});
} else {
InstantiateFunctionDefinition(/*FIXME:*/ Inst.second, Function, true,
- DefinitionRequired, true);
+ DefinitionRequired, AtEndOfTU);
if (Function->isDefined())
Function->setInstantiationIsPending(false);
}
// Definition of a PCH-ed template declaration may be available only in the TU.
if (!LocalOnly && LangOpts.PCHInstantiateTemplates &&
TUKind == TU_Prefix && Function->instantiationIsPending())
- delayedPCHInstantiations.push_back(Inst);
+ DelayedImplicitInstantiations.push_back(Inst);
+ else if (!AtEndOfTU && Function->instantiationIsPending() &&
+ !LocalInstantiation)
+ DelayedImplicitInstantiations.push_back(Inst);
continue;
}
@@ -6627,11 +6640,11 @@ void Sema::PerformPendingInstantiations(bool LocalOnly) {
// Instantiate static data member definitions or variable template
// specializations.
InstantiateVariableDefinition(/*FIXME:*/ Inst.second, Var, true,
- DefinitionRequired, true);
+ DefinitionRequired, AtEndOfTU);
}
- if (!LocalOnly && LangOpts.PCHInstantiateTemplates)
- PendingInstantiations.swap(delayedPCHInstantiations);
+ if (!DelayedImplicitInstantiations.empty())
+ PendingInstantiations.swap(DelayedImplicitInstantiations);
}
void Sema::PerformDependentDiagnostics(const DeclContext *Pattern,
diff --git a/clang/test/CodeGenCXX/function-template-specialization.cpp b/clang/test/CodeGenCXX/function-template-specialization.cpp
index 7728f3dc74624..d41de64c42d0a 100644
--- a/clang/test/CodeGenCXX/function-template-specialization.cpp
+++ b/clang/test/CodeGenCXX/function-template-specialization.cpp
@@ -1,4 +1,5 @@
-// RUN: %clang_cc1 -emit-llvm -triple %itanium_abi_triple %s -o - | FileCheck %s
+// RUN: %clang_cc1 -emit-llvm -Wundefined-func-template -verify -triple %itanium_abi_triple %s -o - | FileCheck %s
+// expected-no-diagnostics
// CHECK-DAG: _ZZN7PR219047GetDataIiEERKibE1i = internal global i32 4
// CHECK-DAG: _ZZN7PR219047GetDataIiEERKibE1i_0 = internal global i32 2
@@ -43,3 +44,19 @@ const int &GetData<int>(bool b) {
return i;
}
}
+
+namespace GH125747 {
+
+template<typename F> constexpr int visit(F f) { return f(0); }
+
+template <class T> int G(T t);
+
+int main() { return visit([](auto s) -> int { return G(s); }); }
+
+template <class T> int G(T t) {
+ return 0;
+}
+
+// CHECK: define linkonce_odr noundef i32 @_ZN8GH1257471GIiEEiT_(i32 noundef %t)
+
+}
>From 242d1d57fa19696797932340509b8aae46937826 Mon Sep 17 00:00:00 2001
From: Younan Zhang <zyn7109 at gmail.com>
Date: Wed, 12 Feb 2025 09:46:48 +0800
Subject: [PATCH 2/2] Fix windows CI
---
clang/test/CodeGenCXX/function-template-specialization.cpp | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/clang/test/CodeGenCXX/function-template-specialization.cpp b/clang/test/CodeGenCXX/function-template-specialization.cpp
index d41de64c42d0a..31c78358d014c 100644
--- a/clang/test/CodeGenCXX/function-template-specialization.cpp
+++ b/clang/test/CodeGenCXX/function-template-specialization.cpp
@@ -57,6 +57,6 @@ template <class T> int G(T t) {
return 0;
}
-// CHECK: define linkonce_odr noundef i32 @_ZN8GH1257471GIiEEiT_(i32 noundef %t)
+// CHECK: define {{.*}} @_ZN8GH1257471GIiEEiT_
}
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