[clang] d9308aa - [clang] don't mark as Elidable CXXConstruct expressions used in NRVO
Matheus Izvekov via cfe-commits
cfe-commits at lists.llvm.org
Tue Sep 21 12:41:28 PDT 2021
Author: Matheus Izvekov
Date: 2021-09-21T21:41:20+02:00
New Revision: d9308aa39b236064a680ca57178af3c731e13e49
URL: https://github.com/llvm/llvm-project/commit/d9308aa39b236064a680ca57178af3c731e13e49
DIFF: https://github.com/llvm/llvm-project/commit/d9308aa39b236064a680ca57178af3c731e13e49.diff
LOG: [clang] don't mark as Elidable CXXConstruct expressions used in NRVO
See PR51862.
The consumers of the Elidable flag in CXXConstructExpr assume that
an elidable construction just goes through a single copy/move construction,
so that the source object is immediately passed as an argument and is the same
type as the parameter itself.
With the implementation of P2266 and after some adjustments to the
implementation of P1825, we started (correctly, as per standard)
allowing more cases where the copy initialization goes through
user defined conversions.
With this patch we stop using this flag in NRVO contexts, to preserve code
that relies on that assumption.
This causes no known functional changes, we just stop firing some asserts
in a cople of included test cases.
Reviewed By: rsmith
Differential Revision: https://reviews.llvm.org/D109800
Added:
clang/test/CodeGenCXX/copy-elision.cpp
Modified:
clang/include/clang/Sema/Initialization.h
clang/lib/AST/ExprConstant.cpp
clang/lib/CodeGen/CGExprCXX.cpp
clang/lib/Sema/Sema.cpp
clang/lib/Sema/SemaCoroutine.cpp
clang/lib/Sema/SemaDeclCXX.cpp
clang/lib/Sema/SemaExpr.cpp
clang/lib/Sema/SemaExprCXX.cpp
clang/lib/Sema/SemaLambda.cpp
clang/lib/Sema/SemaObjCProperty.cpp
clang/lib/Sema/SemaStmt.cpp
clang/test/CodeGen/nrvo-tracking.cpp
Removed:
################################################################################
diff --git a/clang/include/clang/Sema/Initialization.h b/clang/include/clang/Sema/Initialization.h
index 4664861c4e32a..8c1856f208279 100644
--- a/clang/include/clang/Sema/Initialization.h
+++ b/clang/include/clang/Sema/Initialization.h
@@ -298,8 +298,8 @@ class alignas(8) InitializedEntity {
/// Create the initialization entity for the result of a function.
static InitializedEntity InitializeResult(SourceLocation ReturnLoc,
- QualType Type, bool NRVO) {
- return InitializedEntity(EK_Result, ReturnLoc, Type, NRVO);
+ QualType Type) {
+ return InitializedEntity(EK_Result, ReturnLoc, Type);
}
static InitializedEntity InitializeStmtExprResult(SourceLocation ReturnLoc,
@@ -308,20 +308,20 @@ class alignas(8) InitializedEntity {
}
static InitializedEntity InitializeBlock(SourceLocation BlockVarLoc,
- QualType Type, bool NRVO) {
- return InitializedEntity(EK_BlockElement, BlockVarLoc, Type, NRVO);
+ QualType Type) {
+ return InitializedEntity(EK_BlockElement, BlockVarLoc, Type);
}
static InitializedEntity InitializeLambdaToBlock(SourceLocation BlockVarLoc,
- QualType Type, bool NRVO) {
+ QualType Type) {
return InitializedEntity(EK_LambdaToBlockConversionBlockElement,
- BlockVarLoc, Type, NRVO);
+ BlockVarLoc, Type);
}
/// Create the initialization entity for an exception object.
static InitializedEntity InitializeException(SourceLocation ThrowLoc,
- QualType Type, bool NRVO) {
- return InitializedEntity(EK_Exception, ThrowLoc, Type, NRVO);
+ QualType Type) {
+ return InitializedEntity(EK_Exception, ThrowLoc, Type);
}
/// Create the initialization entity for an object allocated via new.
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 296e9e7e5995e..ea7818c43e321 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -9933,10 +9933,19 @@ bool RecordExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E,
return false;
// Avoid materializing a temporary for an elidable copy/move constructor.
- if (E->isElidable() && !ZeroInit)
- if (const MaterializeTemporaryExpr *ME
- = dyn_cast<MaterializeTemporaryExpr>(E->getArg(0)))
+ if (E->isElidable() && !ZeroInit) {
+ // FIXME: This only handles the simplest case, where the source object
+ // is passed directly as the first argument to the constructor.
+ // This should also handle stepping though implicit casts and
+ // and conversion sequences which involve two steps, with a
+ // conversion operator followed by a converting constructor.
+ const Expr *SrcObj = E->getArg(0);
+ assert(SrcObj->isTemporaryObject(Info.Ctx, FD->getParent()));
+ assert(Info.Ctx.hasSameUnqualifiedType(E->getType(), SrcObj->getType()));
+ if (const MaterializeTemporaryExpr *ME =
+ dyn_cast<MaterializeTemporaryExpr>(SrcObj))
return Visit(ME->getSubExpr());
+ }
if (ZeroInit && !ZeroInitialization(E, T))
return false;
diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index d86ae7ad17d68..cc838bf38c6ca 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -609,15 +609,18 @@ CodeGenFunction::EmitCXXConstructExpr(const CXXConstructExpr *E,
return;
// Elide the constructor if we're constructing from a temporary.
- // The temporary check is required because Sema sets this on NRVO
- // returns.
if (getLangOpts().ElideConstructors && E->isElidable()) {
- assert(getContext().hasSameUnqualifiedType(E->getType(),
- E->getArg(0)->getType()));
- if (E->getArg(0)->isTemporaryObject(getContext(), CD->getParent())) {
- EmitAggExpr(E->getArg(0), Dest);
- return;
- }
+ // FIXME: This only handles the simplest case, where the source object
+ // is passed directly as the first argument to the constructor.
+ // This should also handle stepping though implicit casts and
+ // conversion sequences which involve two steps, with a
+ // conversion operator followed by a converting constructor.
+ const Expr *SrcObj = E->getArg(0);
+ assert(SrcObj->isTemporaryObject(getContext(), CD->getParent()));
+ assert(
+ getContext().hasSameUnqualifiedType(E->getType(), SrcObj->getType()));
+ EmitAggExpr(SrcObj, Dest);
+ return;
}
if (const ArrayType *arrayType
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index c997c70d17cef..d260a45867e06 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -2022,7 +2022,7 @@ static void checkEscapingByref(VarDecl *VD, Sema &S) {
Expr *VarRef =
new (S.Context) DeclRefExpr(S.Context, VD, false, T, VK_LValue, Loc);
ExprResult Result;
- auto IE = InitializedEntity::InitializeBlock(Loc, T, false);
+ auto IE = InitializedEntity::InitializeBlock(Loc, T);
if (S.getLangOpts().CPlusPlus2b) {
auto *E = ImplicitCastExpr::Create(S.Context, T, CK_NoOp, VarRef, nullptr,
VK_XValue, FPOptionsOverride());
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index 94c728093e7c9..3d1899a57c72a 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -1533,7 +1533,7 @@ bool CoroutineStmtBuilder::makeGroDeclAndReturnStmt() {
if (GroType->isVoidType()) {
// Trigger a nice error message.
InitializedEntity Entity =
- InitializedEntity::InitializeResult(Loc, FnRetType, false);
+ InitializedEntity::InitializeResult(Loc, FnRetType);
S.PerformCopyInitialization(Entity, SourceLocation(), ReturnValue);
noteMemberDeclaredHere(S, ReturnValue, Fn);
return false;
diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp
index c3fbcc42fbfd3..4c5e5549e805d 100644
--- a/clang/lib/Sema/SemaDeclCXX.cpp
+++ b/clang/lib/Sema/SemaDeclCXX.cpp
@@ -15312,8 +15312,17 @@ Sema::BuildCXXConstructExpr(SourceLocation ConstructLoc, QualType DeclInitType,
// can be omitted by constructing the temporary object
// directly into the target of the omitted copy/move
if (ConstructKind == CXXConstructExpr::CK_Complete && Constructor &&
+ // FIXME: Converting constructors should also be accepted.
+ // But to fix this, the logic that digs down into a CXXConstructExpr
+ // to find the source object needs to handle it.
+ // Right now it assumes the source object is passed directly as the
+ // first argument.
Constructor->isCopyOrMoveConstructor() && hasOneRealArgument(ExprArgs)) {
Expr *SubExpr = ExprArgs[0];
+ // FIXME: Per above, this is also incorrect if we want to accept
+ // converting constructors, as isTemporaryObject will
+ // reject temporaries with
diff erent type from the
+ // CXXRecord itself.
Elidable = SubExpr->isTemporaryObject(
Context, cast<CXXRecordDecl>(FoundDecl->getDeclContext()));
}
diff --git a/clang/lib/Sema/SemaExpr.cpp b/clang/lib/Sema/SemaExpr.cpp
index 7991e4c5e8b0a..8eee366fbec67 100644
--- a/clang/lib/Sema/SemaExpr.cpp
+++ b/clang/lib/Sema/SemaExpr.cpp
@@ -15713,7 +15713,7 @@ ExprResult Sema::ActOnBlockStmtExpr(SourceLocation CaretLoc,
if (!Result.isInvalid()) {
Result = PerformCopyInitialization(
InitializedEntity::InitializeBlock(Var->getLocation(),
- Cap.getCaptureType(), false),
+ Cap.getCaptureType()),
Loc, Result.get());
}
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index e76c4509d7888..f4a27a00a2e2e 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -893,9 +893,8 @@ ExprResult Sema::BuildCXXThrow(SourceLocation OpLoc, Expr *Ex,
if (CheckCXXThrowOperand(OpLoc, ExceptionObjectTy, Ex))
return ExprError();
- InitializedEntity Entity = InitializedEntity::InitializeException(
- OpLoc, ExceptionObjectTy,
- /*NRVO=*/NRInfo.isCopyElidable());
+ InitializedEntity Entity =
+ InitializedEntity::InitializeException(OpLoc, ExceptionObjectTy);
ExprResult Res = PerformMoveOrCopyInitialization(Entity, NRInfo, Ex);
if (Res.isInvalid())
return ExprError();
diff --git a/clang/lib/Sema/SemaLambda.cpp b/clang/lib/Sema/SemaLambda.cpp
index 3784938847b05..286471997db78 100644
--- a/clang/lib/Sema/SemaLambda.cpp
+++ b/clang/lib/Sema/SemaLambda.cpp
@@ -1978,8 +1978,7 @@ ExprResult Sema::BuildBlockForLambdaConversion(SourceLocation CurrentLocation,
CallOperator->markUsed(Context);
ExprResult Init = PerformCopyInitialization(
- InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType(),
- /*NRVO=*/false),
+ InitializedEntity::InitializeLambdaToBlock(ConvLocation, Src->getType()),
CurrentLocation, Src);
if (!Init.isInvalid())
Init = ActOnFinishFullExpr(Init.get(), /*DiscardedValue*/ false);
diff --git a/clang/lib/Sema/SemaObjCProperty.cpp b/clang/lib/Sema/SemaObjCProperty.cpp
index a329d0f22b030..74c73ace3c5ff 100644
--- a/clang/lib/Sema/SemaObjCProperty.cpp
+++ b/clang/lib/Sema/SemaObjCProperty.cpp
@@ -1467,8 +1467,7 @@ Decl *Sema::ActOnPropertyImplDecl(Scope *S,
LoadSelfExpr, true, true);
ExprResult Res = PerformCopyInitialization(
InitializedEntity::InitializeResult(PropertyDiagLoc,
- getterMethod->getReturnType(),
- /*NRVO=*/false),
+ getterMethod->getReturnType()),
PropertyDiagLoc, IvarRefExpr);
if (!Res.isInvalid()) {
Expr *ResExpr = Res.getAs<Expr>();
diff --git a/clang/lib/Sema/SemaStmt.cpp b/clang/lib/Sema/SemaStmt.cpp
index fae2b143219b2..98e6275bfda07 100644
--- a/clang/lib/Sema/SemaStmt.cpp
+++ b/clang/lib/Sema/SemaStmt.cpp
@@ -3653,8 +3653,8 @@ StmtResult Sema::ActOnCapScopeReturnStmt(SourceLocation ReturnLoc,
// In C++ the return statement is handled via a copy initialization.
// the C version of which boils down to CheckSingleAssignmentConstraints.
- InitializedEntity Entity = InitializedEntity::InitializeResult(
- ReturnLoc, FnRetType, NRVOCandidate != nullptr);
+ InitializedEntity Entity =
+ InitializedEntity::InitializeResult(ReturnLoc, FnRetType);
ExprResult Res = PerformMoveOrCopyInitialization(
Entity, NRInfo, RetValExp, SupressSimplerImplicitMoves);
if (Res.isInvalid()) {
@@ -4085,8 +4085,8 @@ StmtResult Sema::BuildReturnStmt(SourceLocation ReturnLoc, Expr *RetValExp) {
// the C version of which boils down to CheckSingleAssignmentConstraints.
if (!HasDependentReturnType && !RetValExp->isTypeDependent()) {
// we have a non-void function with an expression, continue checking
- InitializedEntity Entity = InitializedEntity::InitializeResult(
- ReturnLoc, RetType, NRVOCandidate != nullptr);
+ InitializedEntity Entity =
+ InitializedEntity::InitializeResult(ReturnLoc, RetType);
ExprResult Res = PerformMoveOrCopyInitialization(
Entity, NRInfo, RetValExp, SupressSimplerImplicitMoves);
if (Res.isInvalid()) {
diff --git a/clang/test/CodeGen/nrvo-tracking.cpp b/clang/test/CodeGen/nrvo-tracking.cpp
index 2d6eb9efeca20..be405878f6f9b 100644
--- a/clang/test/CodeGen/nrvo-tracking.cpp
+++ b/clang/test/CodeGen/nrvo-tracking.cpp
@@ -282,3 +282,40 @@ X t5() {
}
} // namespace test_alignas
+
+namespace PR51862 {
+
+template <class T> T test() {
+ T a;
+ T b;
+ if (0)
+ return a;
+ return b;
+}
+
+struct A {
+ A();
+ A(A &);
+ A(int);
+ operator int();
+};
+
+// CHECK-LABEL: define{{.*}} void @_ZN7PR518624testINS_1AEEET_v
+// CHECK: call i32 @_ZN7PR518621AcviEv
+// CHECK-NEXT: call void @_ZN7PR518621AC1Ei
+// CHECK-NEXT: call void @llvm.lifetime.end
+template A test<A>();
+
+struct BSub {};
+struct B : BSub {
+ B();
+ B(B &);
+ B(const BSub &);
+};
+
+// CHECK-LABEL: define{{.*}} void @_ZN7PR518624testINS_1BEEET_v
+// CHECK: call void @_ZN7PR518621BC1ERKNS_4BSubE
+// CHECK-NEXT: call void @llvm.lifetime.end
+template B test<B>();
+
+} // namespace PR51862
diff --git a/clang/test/CodeGenCXX/copy-elision.cpp b/clang/test/CodeGenCXX/copy-elision.cpp
new file mode 100644
index 0000000000000..72b2a5e00264c
--- /dev/null
+++ b/clang/test/CodeGenCXX/copy-elision.cpp
@@ -0,0 +1,34 @@
+// RUN: %clang_cc1 -std=c++14 -triple x86_64-unknown-unknown-gnu -emit-llvm -O1 -fexperimental-new-pass-manager -o - %s | FileCheck %s
+
+template <class T> T test() {
+ return T();
+}
+
+struct A {
+ A();
+ A(A &);
+ A(int);
+ operator int();
+};
+
+// FIXME: There should be copy elision here.
+// CHECK-LABEL: define{{.*}} void @_Z4testI1AET_v
+// CHECK: call void @_ZN1AC1Ev
+// CHECK-NEXT: call i32 @_ZN1AcviEv
+// CHECK-NEXT: call void @_ZN1AC1Ei
+// CHECK-NEXT: call void @llvm.lifetime.end
+template A test<A>();
+
+struct BSub {};
+struct B : BSub {
+ B();
+ B(B &);
+ B(const BSub &);
+};
+
+// FIXME: There should be copy elision here.
+// CHECK-LABEL: define{{.*}} void @_Z4testI1BET_v
+// CHECK: call void @_ZN1BC1Ev
+// CHECK: call void @_ZN1BC1ERK4BSub
+// CHECK-NEXT: call void @llvm.lifetime.end
+template B test<B>();
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