Avoid using rvalue references with trivially copyable types.
Summary:
When the dereference operator returns a value that is trivially
copyable (like a pointer), copy it. After this change, modernize-loop-convert
check can be applied to the whole llvm source code without breaking any build
or test.
Reviewers: alexfh, klimek
Subscribers: alexfh, cfe-commits
Differential Revision: http://reviews.llvm.org/D12675
llvm-svn: 246989
diff --git a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
index b6cb64f..9af7979 100644
--- a/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
+++ b/clang-tools-extra/clang-tidy/modernize/LoopConvertCheck.cpp
@@ -375,7 +375,7 @@
/// by reference.
static bool usagesReturnRValues(const UsageResult &Usages) {
for (const auto &U : Usages) {
- if (!U.Expression->isRValue())
+ if (U.Expression && !U.Expression->isRValue())
return false;
}
return true;
@@ -400,8 +400,7 @@
ASTContext *Context, const VarDecl *IndexVar, const VarDecl *MaybeContainer,
StringRef ContainerString, const UsageResult &Usages,
const DeclStmt *AliasDecl, bool AliasUseRequired, bool AliasFromForInit,
- const ForStmt *TheLoop, bool ContainerNeedsDereference, bool DerefByValue,
- bool DerefByConstRef) {
+ const ForStmt *TheLoop, RangeDescriptor Descriptor) {
auto Diag = diag(TheLoop->getForLoc(), "use range-based for loop instead");
std::string VarName;
@@ -457,16 +456,17 @@
// If an iterator's operator*() returns a 'T&' we can bind that to 'auto&'.
// If operator*() returns 'T' we can bind that to 'auto&&' which will deduce
// to 'T&&&'.
- if (DerefByValue) {
- AutoRefType = Context->getRValueReferenceType(AutoRefType);
+ if (Descriptor.DerefByValue) {
+ if (!Descriptor.IsTriviallyCopyable)
+ AutoRefType = Context->getRValueReferenceType(AutoRefType);
} else {
- if (DerefByConstRef)
+ if (Descriptor.DerefByConstRef)
AutoRefType = Context->getConstType(AutoRefType);
AutoRefType = Context->getLValueReferenceType(AutoRefType);
}
}
- StringRef MaybeDereference = ContainerNeedsDereference ? "*" : "";
+ StringRef MaybeDereference = Descriptor.ContainerNeedsDereference ? "*" : "";
std::string TypeString = AutoRefType.getAsString();
std::string Range = ("(" + TypeString + " " + VarName + " : " +
MaybeDereference + ContainerString + ")")
@@ -518,11 +518,11 @@
/// of the index variable and convert the loop if possible.
void LoopConvertCheck::findAndVerifyUsages(
ASTContext *Context, const VarDecl *LoopVar, const VarDecl *EndVar,
- const Expr *ContainerExpr, const Expr *BoundExpr,
- bool ContainerNeedsDereference, bool DerefByValue, bool DerefByConstRef,
- const ForStmt *TheLoop, LoopFixerKind FixerKind) {
+ const Expr *ContainerExpr, const Expr *BoundExpr, const ForStmt *TheLoop,
+ LoopFixerKind FixerKind, RangeDescriptor Descriptor) {
ForLoopIndexUseVisitor Finder(Context, LoopVar, EndVar, ContainerExpr,
- BoundExpr, ContainerNeedsDereference);
+ BoundExpr,
+ Descriptor.ContainerNeedsDereference);
if (ContainerExpr) {
ComponentFinderASTVisitor ComponentFinder;
@@ -544,15 +544,28 @@
!isDirectMemberExpr(ContainerExpr))
ConfidenceLevel.lowerTo(Confidence::CL_Risky);
} else if (FixerKind == LFK_PseudoArray) {
- if (!DerefByValue && !DerefByConstRef) {
+ if (!Descriptor.DerefByValue && !Descriptor.DerefByConstRef) {
const UsageResult &Usages = Finder.getUsages();
if (usagesAreConst(Usages)) {
- // FIXME: check if the type is trivially copiable.
- DerefByConstRef = true;
+ Descriptor.DerefByConstRef = true;
} else if (usagesReturnRValues(Usages)) {
// If the index usages (dereference, subscript, at) return RValues,
// then we should not use a non-const reference.
- DerefByValue = true;
+ Descriptor.DerefByValue = true;
+ // Try to find the type of the elements on the container from the
+ // usages.
+ for (const Usage &U : Usages) {
+ if (!U.Expression || U.Expression->getType().isNull())
+ continue;
+ QualType Type = U.Expression->getType().getCanonicalType();
+ if (U.IsArrow) {
+ if (!Type->isPointerType())
+ continue;
+ Type = Type->getPointeeType();
+ }
+ Descriptor.IsTriviallyCopyable =
+ Type.isTriviallyCopyableType(*Context);
+ }
}
}
}
@@ -565,7 +578,7 @@
doConversion(Context, LoopVar, getReferencedVariable(ContainerExpr),
ContainerString, Finder.getUsages(), Finder.getAliasDecl(),
Finder.aliasUseRequired(), Finder.aliasFromForInit(), TheLoop,
- ContainerNeedsDereference, DerefByValue, DerefByConstRef);
+ Descriptor);
}
void LoopConvertCheck::registerMatchers(MatchFinder *Finder) {
@@ -618,15 +631,13 @@
ConfidenceLevel.lowerTo(Confidence::CL_Reasonable);
const Expr *ContainerExpr = nullptr;
- bool DerefByValue = false;
- bool DerefByConstRef = false;
- bool ContainerNeedsDereference = false;
+ RangeDescriptor Descriptor{false, false, false, false};
// FIXME: Try to put most of this logic inside a matcher. Currently, matchers
// don't allow the ight-recursive checks in digThroughConstructors.
if (FixerKind == LFK_Iterator) {
ContainerExpr = findContainer(Context, LoopVar->getInit(),
EndVar ? EndVar->getInit() : EndCall,
- &ContainerNeedsDereference);
+ &Descriptor.ContainerNeedsDereference);
QualType InitVarType = InitVar->getType();
QualType CanonicalInitVarType = InitVarType.getCanonicalType();
@@ -643,6 +654,8 @@
// un-qualified pointee types match otherwise we don't use auto.
if (!Context->hasSameUnqualifiedType(InitPointeeType, BeginPointeeType))
return;
+ Descriptor.IsTriviallyCopyable =
+ BeginPointeeType.isTriviallyCopyableType(*Context);
} else {
// Check for qualified types to avoid conversions from non-const to const
// iterator types.
@@ -650,17 +663,19 @@
return;
}
- DerefByValue = Nodes.getNodeAs<QualType>(DerefByValueResultName) != nullptr;
- if (!DerefByValue) {
+ const auto *DerefByValueType =
+ Nodes.getNodeAs<QualType>(DerefByValueResultName);
+ Descriptor.DerefByValue = DerefByValueType;
+ if (!Descriptor.DerefByValue) {
if (const auto *DerefType =
Nodes.getNodeAs<QualType>(DerefByRefResultName)) {
// A node will only be bound with DerefByRefResultName if we're dealing
// with a user-defined iterator type. Test the const qualification of
// the reference type.
- DerefByConstRef = (*DerefType)
- ->getAs<ReferenceType>()
- ->getPointeeType()
- .isConstQualified();
+ Descriptor.DerefByConstRef = (*DerefType)
+ ->getAs<ReferenceType>()
+ ->getPointeeType()
+ .isConstQualified();
} else {
// By nature of the matcher this case is triggered only for built-in
// iterator types (i.e. pointers).
@@ -671,12 +686,14 @@
// If the initializer and variable have both the same type just use auto
// otherwise we test for const qualification of the pointed-at type.
if (!Context->hasSameType(InitPointeeType, BeginPointeeType))
- DerefByConstRef = InitPointeeType.isConstQualified();
+ Descriptor.DerefByConstRef = InitPointeeType.isConstQualified();
}
} else {
// If the dereference operator returns by value then test for the
// canonical const qualification of the init variable type.
- DerefByConstRef = CanonicalInitVarType.isConstQualified();
+ Descriptor.DerefByConstRef = CanonicalInitVarType.isConstQualified();
+ Descriptor.IsTriviallyCopyable =
+ DerefByValueType->isTriviallyCopyableType(*Context);
}
} else if (FixerKind == LFK_PseudoArray) {
if (!EndCall)
@@ -685,7 +702,7 @@
const auto *Member = dyn_cast<MemberExpr>(EndCall->getCallee());
if (!Member)
return;
- ContainerNeedsDereference = Member->isArrow();
+ Descriptor.ContainerNeedsDereference = Member->isArrow();
}
// We must know the container or an array length bound.
@@ -696,8 +713,7 @@
return;
findAndVerifyUsages(Context, LoopVar, EndVar, ContainerExpr, BoundExpr,
- ContainerNeedsDereference, DerefByValue, DerefByConstRef,
- TheLoop, FixerKind);
+ TheLoop, FixerKind, Descriptor);
}
} // namespace modernize