modocache created this revision.
modocache added reviewers: GorNishanov, rsmith, lewissbaker.
Herald added subscribers: cfe-commits, EricWF.
Herald added a project: clang.
modocache edited the summary of this revision.
In the case of a coroutine that takes no arguments,
`Sema::buildCoroutinePromise` constructs a list-initialization
(`clang::InitializationKind::InitKind::IK_DirectList`) of the
promise variable, using a list of empty arguments. So, if one were to
dump the promise `VarDecl` immediately after `Sema::ActOnCoroutineBodyStart`
calls `checkCoroutineContext`, for a coroutine function that takes no
arguments, they'd see the following:
VarDecl 0xb514490 <test.cpp:26:3> col:3 __promise '<dependent type>' callinit
`-ParenListExpr 0xb514510 <col:3> 'NULL TYPE'
But after this patch, the `ParenListExpr` is no longer constructed, and
the promise variable uses default initialization
(`clang::InitializationKind::InitKind::IK_Default`):
VarDecl 0x63100012dae0 <test.cpp:26:3> col:3 __promise '<dependent type>'
As far as I know, there's no case in which list-initialization with no
arguments differs from default initialization, but if I'm wrong please
let me know (and I'll add a test case that demonstrates the change --
but as-is I can't think of a functional test case for this). I think both
comply with the wording of C++20 `[dcl.fct.def.coroutine]p5`:
> _promise-constructor-arguments_ is determined as follows: overload
> resolution is performed on a promise constructor call created by
> assembling an argument list with lvalues `p1 ... pn`. If a viable
> constructor is found (12.4.2), then _promise-constructor-arguments_
> is `(p1, ... , pn)`, otherwise _promise-constructor-arguments_ is
> empty.
Still, I think this patch is an improvement regardless, because it
reduces the size of the AST.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D70555
Files:
clang/lib/Sema/SemaCoroutine.cpp
Index: clang/lib/Sema/SemaCoroutine.cpp
===================================================================
--- clang/lib/Sema/SemaCoroutine.cpp
+++ clang/lib/Sema/SemaCoroutine.cpp
@@ -502,8 +502,9 @@
return nullptr;
auto *ScopeInfo = getCurFunction();
- // Build a list of arguments, based on the coroutine functions arguments,
- // that will be passed to the promise type's constructor.
+
+ // Build a list of arguments, based on the coroutine function's arguments,
+ // that if present will be passed to the promise type's constructor.
llvm::SmallVector<Expr *, 4> CtorArgExprs;
// Add implicit object parameter.
@@ -519,6 +520,7 @@
}
}
+ // Add the coroutine function's parameters.
auto &Moves = ScopeInfo->CoroutineParameterMoves;
for (auto *PD : FD->parameters()) {
if (PD->getType()->isDependentType())
@@ -540,28 +542,33 @@
CtorArgExprs.push_back(RefExpr.get());
}
- // Create an initialization sequence for the promise type using the
- // constructor arguments, wrapped in a parenthesized list expression.
- Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
- CtorArgExprs, FD->getLocation());
- InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
- InitializationKind Kind = InitializationKind::CreateForInit(
- VD->getLocation(), /*DirectInit=*/true, PLE);
- InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
- /*TopLevelOfInitList=*/false,
- /*TreatUnavailableAsInvalid=*/false);
-
- // Attempt to initialize the promise type with the arguments.
- // If that fails, fall back to the promise type's default constructor.
- if (InitSeq) {
- ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
- if (Result.isInvalid()) {
- VD->setInvalidDecl();
- } else if (Result.get()) {
- VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
- VD->setInitStyle(VarDecl::CallInit);
- CheckCompleteVariableDeclaration(VD);
- }
+ // If we have a non-zero number of constructor arguments, try to use them.
+ // Otherwise, fall back to the promise type's default constructor.
+ if (!CtorArgExprs.empty()) {
+ // Create an initialization sequence for the promise type using the
+ // constructor arguments, wrapped in a parenthesized list expression.
+ Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
+ CtorArgExprs, FD->getLocation());
+ InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
+ InitializationKind Kind = InitializationKind::CreateForInit(
+ VD->getLocation(), /*DirectInit=*/true, PLE);
+ InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
+ /*TopLevelOfInitList=*/false,
+ /*TreatUnavailableAsInvalid=*/false);
+
+ // Attempt to initialize the promise type with the arguments.
+ // If that fails, fall back to the promise type's default constructor.
+ if (InitSeq) {
+ ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
+ if (Result.isInvalid()) {
+ VD->setInvalidDecl();
+ } else if (Result.get()) {
+ VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
+ VD->setInitStyle(VarDecl::CallInit);
+ CheckCompleteVariableDeclaration(VD);
+ }
+ } else
+ ActOnUninitializedDecl(VD);
} else
ActOnUninitializedDecl(VD);
Index: clang/lib/Sema/SemaCoroutine.cpp
===================================================================
--- clang/lib/Sema/SemaCoroutine.cpp
+++ clang/lib/Sema/SemaCoroutine.cpp
@@ -502,8 +502,9 @@
return nullptr;
auto *ScopeInfo = getCurFunction();
- // Build a list of arguments, based on the coroutine functions arguments,
- // that will be passed to the promise type's constructor.
+
+ // Build a list of arguments, based on the coroutine function's arguments,
+ // that if present will be passed to the promise type's constructor.
llvm::SmallVector<Expr *, 4> CtorArgExprs;
// Add implicit object parameter.
@@ -519,6 +520,7 @@
}
}
+ // Add the coroutine function's parameters.
auto &Moves = ScopeInfo->CoroutineParameterMoves;
for (auto *PD : FD->parameters()) {
if (PD->getType()->isDependentType())
@@ -540,28 +542,33 @@
CtorArgExprs.push_back(RefExpr.get());
}
- // Create an initialization sequence for the promise type using the
- // constructor arguments, wrapped in a parenthesized list expression.
- Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
- CtorArgExprs, FD->getLocation());
- InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
- InitializationKind Kind = InitializationKind::CreateForInit(
- VD->getLocation(), /*DirectInit=*/true, PLE);
- InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
- /*TopLevelOfInitList=*/false,
- /*TreatUnavailableAsInvalid=*/false);
-
- // Attempt to initialize the promise type with the arguments.
- // If that fails, fall back to the promise type's default constructor.
- if (InitSeq) {
- ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
- if (Result.isInvalid()) {
- VD->setInvalidDecl();
- } else if (Result.get()) {
- VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
- VD->setInitStyle(VarDecl::CallInit);
- CheckCompleteVariableDeclaration(VD);
- }
+ // If we have a non-zero number of constructor arguments, try to use them.
+ // Otherwise, fall back to the promise type's default constructor.
+ if (!CtorArgExprs.empty()) {
+ // Create an initialization sequence for the promise type using the
+ // constructor arguments, wrapped in a parenthesized list expression.
+ Expr *PLE = ParenListExpr::Create(Context, FD->getLocation(),
+ CtorArgExprs, FD->getLocation());
+ InitializedEntity Entity = InitializedEntity::InitializeVariable(VD);
+ InitializationKind Kind = InitializationKind::CreateForInit(
+ VD->getLocation(), /*DirectInit=*/true, PLE);
+ InitializationSequence InitSeq(*this, Entity, Kind, CtorArgExprs,
+ /*TopLevelOfInitList=*/false,
+ /*TreatUnavailableAsInvalid=*/false);
+
+ // Attempt to initialize the promise type with the arguments.
+ // If that fails, fall back to the promise type's default constructor.
+ if (InitSeq) {
+ ExprResult Result = InitSeq.Perform(*this, Entity, Kind, CtorArgExprs);
+ if (Result.isInvalid()) {
+ VD->setInvalidDecl();
+ } else if (Result.get()) {
+ VD->setInit(MaybeCreateExprWithCleanups(Result.get()));
+ VD->setInitStyle(VarDecl::CallInit);
+ CheckCompleteVariableDeclaration(VD);
+ }
+ } else
+ ActOnUninitializedDecl(VD);
} else
ActOnUninitializedDecl(VD);
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