r305862 - Prevent devirtualization of calls to un-instantiated functions.
Sunil Srivastava via cfe-commits
cfe-commits at lists.llvm.org
Tue Jun 20 15:08:45 PDT 2017
Author: ssrivastava
Date: Tue Jun 20 17:08:44 2017
New Revision: 305862
URL: http://llvm.org/viewvc/llvm-project?rev=305862&view=rev
Log:
Prevent devirtualization of calls to un-instantiated functions.
PR 27895
Differential Revision: https://reviews.llvm.org/D22057
Added:
cfe/trunk/test/CodeGen/no-devirt.cpp
Modified:
cfe/trunk/include/clang/AST/Decl.h
cfe/trunk/lib/CodeGen/CGClass.cpp
cfe/trunk/lib/Sema/Sema.cpp
cfe/trunk/lib/Sema/SemaExpr.cpp
cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
Modified: cfe/trunk/include/clang/AST/Decl.h
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/AST/Decl.h?rev=305862&r1=305861&r2=305862&view=diff
==============================================================================
--- cfe/trunk/include/clang/AST/Decl.h (original)
+++ cfe/trunk/include/clang/AST/Decl.h Tue Jun 20 17:08:44 2017
@@ -1656,6 +1656,7 @@ private:
unsigned HasImplicitReturnZero : 1;
unsigned IsLateTemplateParsed : 1;
unsigned IsConstexpr : 1;
+ unsigned InstantiationIsPending:1;
/// \brief Indicates if the function uses __try.
unsigned UsesSEHTry : 1;
@@ -1751,6 +1752,7 @@ protected:
IsDeleted(false), IsTrivial(false), IsDefaulted(false),
IsExplicitlyDefaulted(false), HasImplicitReturnZero(false),
IsLateTemplateParsed(false), IsConstexpr(isConstexprSpecified),
+ InstantiationIsPending(false),
UsesSEHTry(false), HasSkippedBody(false), WillHaveBody(false),
EndRangeLoc(NameInfo.getEndLoc()), TemplateOrSpecialization(),
DNLoc(NameInfo.getInfo()) {}
@@ -1943,6 +1945,15 @@ public:
bool isConstexpr() const { return IsConstexpr; }
void setConstexpr(bool IC) { IsConstexpr = IC; }
+ /// \brief Whether the instantiation of this function is pending.
+ /// This bit is set when the decision to instantiate this function is made
+ /// and unset if and when the function body is created. That leaves out
+ /// cases where instantiation did not happen because the template definition
+ /// was not seen in this TU. This bit remains set in those cases, under the
+ /// assumption that the instantiation will happen in some other TU.
+ bool instantiationIsPending() const { return InstantiationIsPending; }
+ void setInstantiationIsPending(bool IC) { InstantiationIsPending = IC; }
+
/// \brief Indicates the function uses __try.
bool usesSEHTry() const { return UsesSEHTry; }
void setUsesSEHTry(bool UST) { UsesSEHTry = UST; }
Modified: cfe/trunk/lib/CodeGen/CGClass.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGClass.cpp?rev=305862&r1=305861&r2=305862&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGClass.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGClass.cpp Tue Jun 20 17:08:44 2017
@@ -2770,10 +2770,19 @@ CodeGenFunction::CanDevirtualizeMemberFu
// We can devirtualize calls on an object accessed by a class member access
// expression, since by C++11 [basic.life]p6 we know that it can't refer to
- // a derived class object constructed in the same location.
+ // a derived class object constructed in the same location. However, we avoid
+ // devirtualizing a call to a template function that we could instantiate
+ // implicitly, but have not decided to do so. This is needed because if this
+ // function does not get instantiated, the devirtualization will create a
+ // direct call to a function whose body may not exist. In contrast, calls to
+ // template functions that are not defined in this TU are allowed to be
+ // devirtualized under assumption that it is user responsibility to
+ // instantiate them in some other TU.
if (const MemberExpr *ME = dyn_cast<MemberExpr>(Base))
if (const ValueDecl *VD = dyn_cast<ValueDecl>(ME->getMemberDecl()))
- return VD->getType()->isRecordType();
+ return VD->getType()->isRecordType() &&
+ (MD->instantiationIsPending() || MD->isDefined() ||
+ !MD->isImplicitlyInstantiable());
// Likewise for calls on an object accessed by a (non-reference) pointer to
// member access.
Modified: cfe/trunk/lib/Sema/Sema.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/Sema.cpp?rev=305862&r1=305861&r2=305862&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/Sema.cpp (original)
+++ cfe/trunk/lib/Sema/Sema.cpp Tue Jun 20 17:08:44 2017
@@ -740,6 +740,9 @@ void Sema::ActOnEndOfTranslationUnit() {
// Load pending instantiations from the external source.
SmallVector<PendingImplicitInstantiation, 4> Pending;
ExternalSource->ReadPendingInstantiations(Pending);
+ for (auto PII : Pending)
+ if (auto Func = dyn_cast<FunctionDecl>(PII.first))
+ Func->setInstantiationIsPending(true);
PendingInstantiations.insert(PendingInstantiations.begin(),
Pending.begin(), Pending.end());
}
Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=305862&r1=305861&r2=305862&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Tue Jun 20 17:08:44 2017
@@ -13732,6 +13732,7 @@ void Sema::MarkFunctionReferenced(Source
// call to such a function.
InstantiateFunctionDefinition(PointOfInstantiation, Func);
else {
+ Func->setInstantiationIsPending(true);
PendingInstantiations.push_back(std::make_pair(Func,
PointOfInstantiation));
// Notify the consumer that a function was implicitly instantiated.
Modified: cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp?rev=305862&r1=305861&r2=305862&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp (original)
+++ cfe/trunk/lib/Sema/SemaTemplateInstantiateDecl.cpp Tue Jun 20 17:08:44 2017
@@ -3782,6 +3782,7 @@ void Sema::InstantiateFunctionDefinition
// Try again at the end of the translation unit (at which point a
// definition will be required).
assert(!Recursive);
+ Function->setInstantiationIsPending(true);
PendingInstantiations.push_back(
std::make_pair(Function, PointOfInstantiation));
} else if (TSK == TSK_ImplicitInstantiation) {
@@ -3801,6 +3802,7 @@ void Sema::InstantiateFunctionDefinition
// Postpone late parsed template instantiations.
if (PatternDecl->isLateTemplateParsed() &&
!LateTemplateParser) {
+ Function->setInstantiationIsPending(true);
PendingInstantiations.push_back(
std::make_pair(Function, PointOfInstantiation));
return;
@@ -5146,6 +5148,8 @@ void Sema::PerformPendingInstantiations(
TSK_ExplicitInstantiationDefinition;
InstantiateFunctionDefinition(/*FIXME:*/Inst.second, Function, true,
DefinitionRequired, true);
+ if (Function->isDefined())
+ Function->setInstantiationIsPending(false);
continue;
}
Added: cfe/trunk/test/CodeGen/no-devirt.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGen/no-devirt.cpp?rev=305862&view=auto
==============================================================================
--- cfe/trunk/test/CodeGen/no-devirt.cpp (added)
+++ cfe/trunk/test/CodeGen/no-devirt.cpp Tue Jun 20 17:08:44 2017
@@ -0,0 +1,59 @@
+// RUN: %clang_cc1 %s -DUSEIT -triple %itanium_abi_triple -emit-llvm -o - | FileCheck %s
+
+// Test with decls and template defs in pch, and just use in .cpp
+// RUN: %clang_cc1 %s -DTMPL_DEF_IN_HEADER -triple %itanium_abi_triple -emit-pch -o %t
+// RUN: %clang_cc1 %s -DTMPL_DEF_IN_HEADER -DUSEIT -triple %itanium_abi_triple -include-pch %t -emit-llvm -o - | FileCheck %s
+
+// Test with A in pch, and B and C in main
+// Test with just decls in pch, and template defs and use in .cpp
+// RUN: %clang_cc1 %s -triple %itanium_abi_triple -emit-pch -o %t
+// RUN: %clang_cc1 %s -DUSEIT -triple %itanium_abi_triple -include-pch %t -emit-llvm -o - | FileCheck %s
+
+#ifndef HEADER
+#define HEADER
+template < typename T, int N = 0 > class TmplWithArray {
+public:
+ virtual T& operator [] (int idx);
+ virtual T& func1 (int idx);
+ virtual T& func2 (int idx);
+ T ar[N+1];
+};
+struct Wrapper {
+ TmplWithArray<bool, 10> data;
+ bool indexIt(int a) {
+ if (a > 6) return data[a] ; // Should not devirtualize
+ if (a > 4) return data.func1(a); // Should devirtualize
+ return data.func2(a); // Should devirtualize
+ }
+};
+
+#ifdef TMPL_DEF_IN_HEADER
+template <typename T, int N> T& TmplWithArray<T, N >::operator[](int idx) {
+ return ar[idx];
+}
+template <typename T, int N> T& TmplWithArray<T, N >::func1(int idx) {
+ return ar[idx];
+}
+#endif // TMPL_DEF_IN_HEADER
+#endif // HEADER
+
+#ifdef USEIT
+#ifndef TMPL_DEF_IN_HEADER
+template <typename T, int N> T& TmplWithArray<T, N >::operator[](int idx) {
+ return ar[idx];
+}
+template <typename T, int N> T& TmplWithArray<T, N >::func1(int idx) {
+ return ar[idx];
+}
+#endif // !TMPL_DEF_IN_HEADER
+extern Wrapper ew;
+bool stuff(int p)
+{
+ return ew.indexIt(p);
+}
+#endif
+
+// CHECK-NOT: call {{.*}} @_ZN13TmplWithArrayIbLi10EEixEi
+// CHECK-DAG: call {{.*}} @_ZN13TmplWithArrayIbLi10EE5func1Ei
+// CHECK-DAG: call {{.*}} @_ZN13TmplWithArrayIbLi10EE5func2Ei
+
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