Revert r335019 "Update NRVO logic to support early return (Attempt 2)"
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@335022 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h
index 0a0b2c1..c10ca9e 100644
--- a/include/clang/AST/Decl.h
+++ b/include/clang/AST/Decl.h
@@ -879,12 +879,6 @@
DAK_Normal
};
- enum NRVOMode {
- NRVO_Candidate,
- NRVO_Disabled,
- NRVO_Enabled,
- };
-
class ParmVarDeclBitfields {
friend class ASTDeclReader;
friend class ParmVarDecl;
@@ -937,7 +931,7 @@
/// Whether this local variable could be allocated in the return
/// slot of its function, enabling the named return value optimization
/// (NRVO).
- unsigned NRVOMode : 2;
+ unsigned NRVOVariable : 1;
/// Whether this variable is the for-range-declaration in a C++0x
/// for-range statement.
@@ -1325,20 +1319,12 @@
/// return slot when returning from the function. Within the function body,
/// each return that returns the NRVO object will have this variable as its
/// NRVO candidate.
- NRVOMode getNRVOMode() const {
- if (isa<ParmVarDecl>(this))
- return NRVO_Disabled;
- return static_cast<NRVOMode>(NonParmVarDeclBits.NRVOMode);
- }
- bool isNRVOCandidate() const {
- return isa<ParmVarDecl>(this) ? false : NonParmVarDeclBits.NRVOMode == NRVO_Candidate;
- }
bool isNRVOVariable() const {
- return isa<ParmVarDecl>(this) ? false : NonParmVarDeclBits.NRVOMode == NRVO_Enabled;
+ return isa<ParmVarDecl>(this) ? false : NonParmVarDeclBits.NRVOVariable;
}
void setNRVOVariable(bool NRVO) {
assert(!isa<ParmVarDecl>(this));
- NonParmVarDeclBits.NRVOMode = NRVO ? NRVO_Enabled : NRVO_Disabled;
+ NonParmVarDeclBits.NRVOVariable = NRVO;
}
/// Determine whether this variable is the for-range-declaration in
diff --git a/include/clang/Sema/Scope.h b/include/clang/Sema/Scope.h
index 298c546..a3379ff 100644
--- a/include/clang/Sema/Scope.h
+++ b/include/clang/Sema/Scope.h
@@ -201,6 +201,10 @@
/// Used to determine if errors occurred in this scope.
DiagnosticErrorTrap ErrorTrap;
+ /// A lattice consisting of undefined, a single NRVO candidate variable in
+ /// this scope, or over-defined. The bit is true when over-defined.
+ llvm::PointerIntPair<VarDecl *, 1, bool> NRVO;
+
void setFlags(Scope *Parent, unsigned F);
public:
@@ -462,7 +466,23 @@
UsingDirectives.end());
}
- void setNRVOCandidate(VarDecl *Candidate);
+ void addNRVOCandidate(VarDecl *VD) {
+ if (NRVO.getInt())
+ return;
+ if (NRVO.getPointer() == nullptr) {
+ NRVO.setPointer(VD);
+ return;
+ }
+ if (NRVO.getPointer() != VD)
+ setNoNRVO();
+ }
+
+ void setNoNRVO() {
+ NRVO.setInt(true);
+ NRVO.setPointer(nullptr);
+ }
+
+ void mergeNRVOIntoParent();
/// Init - This is used by the parser to implement scope caching.
void Init(Scope *parent, unsigned flags);
diff --git a/lib/Sema/Scope.cpp b/lib/Sema/Scope.cpp
index 5a46ba2..eae5a32 100644
--- a/lib/Sema/Scope.cpp
+++ b/lib/Sema/Scope.cpp
@@ -92,6 +92,7 @@
UsingDirectives.clear();
Entity = nullptr;
ErrorTrap.reset();
+ NRVO.setPointerAndInt(nullptr, 0);
}
bool Scope::containedInPrototypeScope() const {
@@ -118,15 +119,19 @@
Flags |= FlagsToSet;
}
-void Scope::setNRVOCandidate(VarDecl *Candidate) {
- for (Decl *D : DeclsInScope) {
- VarDecl *VD = dyn_cast<VarDecl>(D);
- if (VD && VD != Candidate && VD->isNRVOCandidate())
- VD->setNRVOVariable(false);
+void Scope::mergeNRVOIntoParent() {
+ if (VarDecl *Candidate = NRVO.getPointer()) {
+ if (isDeclScope(Candidate))
+ Candidate->setNRVOVariable(true);
}
- if (Scope *parent = getParent())
- parent->setNRVOCandidate(Candidate);
+ if (getEntity())
+ return;
+
+ if (NRVO.getInt())
+ getParent()->setNoNRVO();
+ else if (NRVO.getPointer())
+ getParent()->addNRVOCandidate(NRVO.getPointer());
}
LLVM_DUMP_METHOD void Scope::dump() const { dumpImpl(llvm::errs()); }
@@ -186,4 +191,9 @@
OS << "MSCurManglingNumber: " << getMSCurManglingNumber() << '\n';
if (const DeclContext *DC = getEntity())
OS << "Entity : (clang::DeclContext*)" << DC << '\n';
+
+ if (NRVO.getInt())
+ OS << "NRVO not allowed\n";
+ else if (NRVO.getPointer())
+ OS << "NRVO candidate : (clang::VarDecl*)" << NRVO.getPointer() << '\n';
}
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index 4c98ffe..f6faf38 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -1798,6 +1798,8 @@
}
void Sema::ActOnPopScope(SourceLocation Loc, Scope *S) {
+ S->mergeNRVOIntoParent();
+
if (S->decl_empty()) return;
assert((S->getFlags() & (Scope::DeclScope | Scope::TemplateParamScope)) &&
"Scope shouldn't contain decls!");
@@ -12561,24 +12563,21 @@
/// optimization.
///
/// Each of the variables that is subject to the named return value
-/// optimization will be marked as NRVO variable candidates in the AST, and any
+/// optimization will be marked as NRVO variables in the AST, and any
/// return statement that has a marked NRVO variable as its NRVO candidate can
/// use the named return value optimization.
///
-/// This function applies a very simplistic algorithm for NRVO: if every
-/// reachable return statement in the scope of a variable has the same NRVO
-/// candidate, that candidate is an NRVO variable.
+/// This function applies a very simplistic algorithm for NRVO: if every return
+/// statement in the scope of a variable has the same NRVO candidate, that
+/// candidate is an NRVO variable.
void Sema::computeNRVO(Stmt *Body, FunctionScopeInfo *Scope) {
- for (ReturnStmt *Return : Scope->Returns) {
- const VarDecl *Candidate = Return->getNRVOCandidate();
- if (!Candidate)
- continue;
+ ReturnStmt **Returns = Scope->Returns.data();
- if (Candidate->isNRVOCandidate())
- const_cast<VarDecl*>(Candidate)->setNRVOVariable(true);
-
- if (!Candidate->isNRVOVariable())
- Return->setNRVOCandidate(nullptr);
+ for (unsigned I = 0, E = Scope->Returns.size(); I != E; ++I) {
+ if (const VarDecl *NRVOCandidate = Returns[I]->getNRVOCandidate()) {
+ if (!NRVOCandidate->isNRVOVariable())
+ Returns[I]->setNRVOCandidate(nullptr);
+ }
}
}
@@ -12713,8 +12712,12 @@
else if (CXXDestructorDecl *Destructor = dyn_cast<CXXDestructorDecl>(FD))
MarkVTableUsed(FD->getLocation(), Destructor->getParent());
- // Try to apply the named return value optimization.
- computeNRVO(Body, getCurFunction());
+ // Try to apply the named return value optimization. We have to check
+ // if we can do this here because lambdas keep return statements around
+ // to deduce an implicit return type.
+ if (FD->getReturnType()->isRecordType() &&
+ (!getLangOpts().CPlusPlus || !FD->isDependentContext()))
+ computeNRVO(Body, getCurFunction());
}
// GNU warning -Wmissing-prototypes:
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 220d690..aeedd6b 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -13385,9 +13385,13 @@
if (Body && getCurFunction()->HasPotentialAvailabilityViolations)
DiagnoseUnguardedAvailabilityViolations(BSI->TheDecl);
- // Try to apply the named return value optimization.
- computeNRVO(Body, BSI);
-
+ // Try to apply the named return value optimization. We have to check again
+ // if we can do this, though, because blocks keep return statements around
+ // to deduce an implicit return type.
+ if (getLangOpts().CPlusPlus && RetTy->isRecordType() &&
+ !BSI->TheDecl->isDependentContext())
+ computeNRVO(Body, BSI);
+
BlockExpr *Result = new (Context) BlockExpr(BSI->TheDecl, BlockTy);
AnalysisBasedWarnings::Policy WP = AnalysisWarnings.getDefaultPolicy();
PopFunctionScopeInfo(&WP, Result->getBlockDecl(), Result);
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 04f5114..ccf25ee 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -3455,9 +3455,12 @@
ExpressionEvaluationContext::DiscardedStatement)
return R;
- VarDecl *VD =
- const_cast<VarDecl*>(cast<ReturnStmt>(R.get())->getNRVOCandidate());
- CurScope->setNRVOCandidate(VD);
+ if (VarDecl *VD =
+ const_cast<VarDecl*>(cast<ReturnStmt>(R.get())->getNRVOCandidate())) {
+ CurScope->addNRVOCandidate(VD);
+ } else {
+ CurScope->setNoNRVO();
+ }
CheckJumpOutOfSEHFinally(*this, ReturnLoc, *CurScope->getFnParent());
diff --git a/lib/Sema/SemaTemplateInstantiateDecl.cpp b/lib/Sema/SemaTemplateInstantiateDecl.cpp
index 7e38dcc..68857d9 100644
--- a/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -740,13 +740,12 @@
SemaRef.BuildVariableInstantiation(Var, D, TemplateArgs, LateAttrs, Owner,
StartingScope, InstantiatingVarTemplate);
- bool NRVO = false;
if (D->isNRVOVariable()) {
QualType ReturnType = cast<FunctionDecl>(DC)->getReturnType();
if (SemaRef.isCopyElisionCandidate(ReturnType, Var, Sema::CES_Strict))
- NRVO = true;
+ Var->setNRVOVariable(true);
}
- Var->setNRVOVariable(NRVO);
+
Var->setImplicit(D->isImplicit());
return Var;
diff --git a/lib/Serialization/ASTReaderDecl.cpp b/lib/Serialization/ASTReaderDecl.cpp
index 699a98c..a1ce26d 100644
--- a/lib/Serialization/ASTReaderDecl.cpp
+++ b/lib/Serialization/ASTReaderDecl.cpp
@@ -1326,7 +1326,7 @@
VD->NonParmVarDeclBits.IsThisDeclarationADemotedDefinition =
Record.readInt();
VD->NonParmVarDeclBits.ExceptionVar = Record.readInt();
- VD->NonParmVarDeclBits.NRVOMode = Record.readInt();
+ VD->NonParmVarDeclBits.NRVOVariable = Record.readInt();
VD->NonParmVarDeclBits.CXXForRangeDecl = Record.readInt();
VD->NonParmVarDeclBits.ObjCForDecl = Record.readInt();
VD->NonParmVarDeclBits.ARCPseudoStrong = Record.readInt();
diff --git a/lib/Serialization/ASTWriterDecl.cpp b/lib/Serialization/ASTWriterDecl.cpp
index c1f983e..cf35a2b 100644
--- a/lib/Serialization/ASTWriterDecl.cpp
+++ b/lib/Serialization/ASTWriterDecl.cpp
@@ -918,7 +918,7 @@
if (!isa<ParmVarDecl>(D)) {
Record.push_back(D->isThisDeclarationADemotedDefinition());
Record.push_back(D->isExceptionVariable());
- Record.push_back(D->getNRVOMode());
+ Record.push_back(D->isNRVOVariable());
Record.push_back(D->isCXXForRangeDecl());
Record.push_back(D->isObjCForDecl());
Record.push_back(D->isARCPseudoStrong());
@@ -2031,7 +2031,7 @@
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // InitStyle
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // IsThisDeclarationADemotedDefinition
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isExceptionVariable
- Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 2)); // NRVOMode
+ Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isNRVOVariable
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isCXXForRangeDecl
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isObjCForDecl
Abv->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Fixed, 1)); // isARCPseudoStrong
diff --git a/test/CodeGenCXX/nrvo-noopt.cpp b/test/CodeGenCXX/nrvo-noopt.cpp
deleted file mode 100644
index 46da7cd..0000000
--- a/test/CodeGenCXX/nrvo-noopt.cpp
+++ /dev/null
@@ -1,58 +0,0 @@
-// RUN: %clang_cc1 -emit-llvm -o - %s | FileCheck %s
-
-struct X {
- X();
- X(X&&);
-};
-
-// CHECK-LABEL: define void @_Z7test_00b
-X test_00(bool b) {
- if (b) {
- // CHECK-NOT: call void @_ZN1XC1EOS_
- // CHECK: call void @_ZN1XC1Ev
- // CHECK-NEXT: br label %return
- X x;
- return x;
- } else {
- // CHECK-NOT: call void @_ZN1XC1EOS_
- // CHECK: call void @_ZN1XC1Ev
- // CHECK-NEXT: br label %return
- X x;
- return x;
- }
-}
-
-// CHECK-LABEL: define void @_Z7test_01b
-X test_01(bool b) {
- if (b) {
- // CHECK-NOT: call void @_ZN1XC1EOS_
- // CHECK: call void @_ZN1XC1Ev
- // CHECK-NEXT: br label %return
- X x;
- return x;
- }
- // CHECK-NOT: call void @_ZN1XC1EOS_
- // CHECK: call void @_ZN1XC1Ev
- // CHECK-NEXT: br label %return
- X x;
- return x;
-}
-
-// CHECK-LABEL: define void @_Z7test_02b
-X test_02(bool b) {
- // CHECK: call void @_ZN1XC1Ev
- X x;
-
- if (b) {
- // CHECK-NOT: call void @_ZN1XC1EOS_
- // CHECK: call void @_ZN1XC1Ev
- // CHECK-NEXT: br label %return
- X y;
- return y;
- }
-
- // CHECK-NOT: call void @_ZN1XC1Ev
- // CHECK: call void @_ZN1XC1EOS_
- // CHECK-NEXT: br label %return
- return x;
-}
diff --git a/test/CodeGenCXX/nrvo.cpp b/test/CodeGenCXX/nrvo.cpp
index 1da4308..0f359b9 100644
--- a/test/CodeGenCXX/nrvo.cpp
+++ b/test/CodeGenCXX/nrvo.cpp
@@ -130,13 +130,17 @@
}
// CHECK-LABEL: define void @_Z5test3b
-X test3(bool B, X x) {
+X test3(bool B) {
// CHECK: tail call {{.*}} @_ZN1XC1Ev
+ // CHECK-NOT: call {{.*}} @_ZN1XC1ERKS_
+ // CHECK: call {{.*}} @_ZN1XC1Ev
+ // CHECK: call {{.*}} @_ZN1XC1ERKS_
if (B) {
X y;
return y;
}
- // CHECK: tail call {{.*}} @_ZN1XC1ERKS_
+ // FIXME: we should NRVO this variable too.
+ X x;
return x;
}
@@ -187,13 +191,9 @@
}
// CHECK-LABEL: define void @_Z5test7b
-// CHECK-EH-LABEL: define void @_Z5test7b
X test7(bool b) {
// CHECK: tail call {{.*}} @_ZN1XC1Ev
// CHECK-NEXT: ret
-
- // CHECK-EH: tail call {{.*}} @_ZN1XC1Ev
- // CHECK-EH-NEXT: ret
if (b) {
X x;
return x;
@@ -202,14 +202,10 @@
}
// CHECK-LABEL: define void @_Z5test8b
-// CHECK-EH-LABEL: define void @_Z5test8b
X test8(bool b) {
// CHECK: tail call {{.*}} @_ZN1XC1Ev
// CHECK-NEXT: ret
-
- // CHECK-EH: tail call {{.*}} @_ZN1XC1Ev
- // CHECK-EH-NEXT: ret
-if (b) {
+ if (b) {
X x;
return x;
} else {
@@ -225,37 +221,4 @@
// CHECK-LABEL: define linkonce_odr void @_ZN1YIiE1fEv
// CHECK: tail call {{.*}} @_ZN1YIiEC1Ev
-// CHECK-LABEL: define void @_Z6test10b
-X test10(bool B, X x) {
- if (B) {
- // CHECK: tail call {{.*}} @_ZN1XC1ERKS_
- // CHECK-EH: tail call {{.*}} @_ZN1XC1ERKS_
- return x;
- }
- // CHECK: tail call {{.*}} @_ZN1XC1Ev
- // CHECK-NOT: call {{.*}} @_ZN1XC1ERKS_
-
- // CHECK-EH: tail call {{.*}} @_ZN1XC1Ev
- // CHECK-EH-NOT: call {{.*}} @_ZN1XC1ERKS_
- X y;
- return y;
-}
-
-// CHECK-LABEL: define {{.*}} void @_Z6test11I1XET_v
-// CHECK-EH-LABEL: define {{.*}} void @_Z6test11I1XET_v
-template <typename T>
-T test11() {
- // CHECK: tail call {{.*}} @_ZN1XC1Ev
- // CHECK-NEXT: ret void
-
- // CHECK-EH: tail call {{.*}} @_ZN1XC1Ev
- // CHECK-EH-NEXT: ret void
- T t;
- return t;
-}
-
-void test12() {
- test11<X>();
-}
-
// CHECK-EH-03: attributes [[NR_NUW]] = { noreturn nounwind }
diff --git a/test/SemaCXX/nrvo-ast.cpp b/test/SemaCXX/nrvo-ast.cpp
deleted file mode 100644
index 63fac00..0000000
--- a/test/SemaCXX/nrvo-ast.cpp
+++ /dev/null
@@ -1,153 +0,0 @@
-// RUN: %clang_cc1 -fcxx-exceptions -fsyntax-only -ast-dump -o - %s | FileCheck %s
-
-struct X {
- X();
- X(const X&);
- X(X&&);
-};
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_00
-X test_00() {
- // CHECK: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- return x;
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_01
-X test_01(bool b) {
- // CHECK: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- if (b)
- return x;
- return x;
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_02
-X test_02(bool b) {
- // CHECK-NOT: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- // CHECK-NOT: VarDecl {{.*}} y {{.*}} nrvo
- X y;
- if (b)
- return y;
- return x;
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_03
-X test_03(bool b) {
- if (b) {
- // CHECK: VarDecl {{.*}} y {{.*}} nrvo
- X y;
- return y;
- }
- // CHECK: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- return x;
-}
-
-extern "C" _Noreturn void exit(int) throw();
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_04
-X test_04(bool b) {
- {
- // CHECK: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- if (b)
- return x;
- }
- exit(1);
-}
-
-void may_throw();
-// CHECK-LABEL: FunctionDecl {{.*}} test_05
-X test_05() {
- try {
- may_throw();
- return X();
- } catch (X x) {
- // CHECK-NOT: VarDecl {{.*}} x {{.*}} nrvo
- return x;
- }
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_06
-X test_06() {
- // CHECK-NOT: VarDecl {{.*}} x {{.*}} nrvo
- X x __attribute__((aligned(8)));
- return x;
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_07
-X test_07(bool b) {
- if (b) {
- // CHECK: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- return x;
- }
- return X();
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_08
-X test_08(bool b) {
- if (b) {
- // CHECK: VarDecl {{.*}} x {{.*}} nrvo
- X x;
- return x;
- } else {
- // CHECK: VarDecl {{.*}} y {{.*}} nrvo
- X y;
- return y;
- }
-}
-
-template <typename T>
-struct Y {
- Y();
- // CHECK-LABEL: CXXMethodDecl {{.*}} test_09 'Y<T> ()'
- // CHECK: VarDecl {{.*}} y 'Y<T>' nrvo
-
- // CHECK-LABEL: CXXMethodDecl {{.*}} test_09 'Y<int> ()'
- // CHECK: VarDecl {{.*}} y 'Y<int>' nrvo
- static Y test_09() {
- Y y;
- return y;
- }
-};
-
-struct Z {
- Z(const X&);
-};
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_10 'A ()'
-// CHECK: VarDecl {{.*}} b 'B' nrvo
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_10 'X ()'
-// CHECK: VarDecl {{.*}} b {{.*}} nrvo
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_10 'Z ()'
-// CHECK-NOT: VarDecl {{.*}} b {{.*}} nrvo
-template <typename A, typename B>
-A test_10() {
- B b;
- return b;
-}
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_11 'A (bool)'
-// CHECK-NOT: VarDecl {{.*}} a {{.*}} nrvo
-
-// CHECK-LABEL: FunctionDecl {{.*}} test_11 'X (bool)'
-// CHECK-NOT: VarDecl {{.*}} a {{.*}} nrvo
-template <typename A>
-A test_11(bool b) {
- A a;
- if (b)
- return A();
- return a;
-}
-
-void instantiate() {
- Y<int>::test_09();
- test_10<X, X>();
- test_10<Z, X>();
- test_11<X>(true);
-}
