r236075 - Add -Wpessimizing-move and -Wredundant-move warnings.
Richard Trieu
rtrieu at google.com
Tue Apr 28 18:52:18 PDT 2015
Author: rtrieu
Date: Tue Apr 28 20:52:17 2015
New Revision: 236075
URL: http://llvm.org/viewvc/llvm-project?rev=236075&view=rev
Log:
Add -Wpessimizing-move and -Wredundant-move warnings.
-Wpessimizing-move warns when a call to std::move would prevent copy elision
if the argument was not wrapped in a call. This happens when moving a local
variable in a return statement when the variable is the same type as the
return type or using a move to create a new object from a temporary object.
-Wredundant-move warns when an implicit move would already be made, so the
std::move call is not needed, such as when moving a local variable in a return
that is different from the return type.
Differential Revision: http://reviews.llvm.org/D7633
Added:
cfe/trunk/test/SemaCXX/warn-pessmizing-move.cpp
cfe/trunk/test/SemaCXX/warn-redundant-move.cpp
Modified:
cfe/trunk/include/clang/Basic/DiagnosticGroups.td
cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
cfe/trunk/lib/Sema/SemaInit.cpp
Modified: cfe/trunk/include/clang/Basic/DiagnosticGroups.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticGroups.td?rev=236075&r1=236074&r2=236075&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticGroups.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticGroups.td Tue Apr 28 20:52:17 2015
@@ -286,6 +286,7 @@ def DeprecatedObjCIsaUsage : DiagGroup<"
def ExplicitInitializeCall : DiagGroup<"explicit-initialize-call">;
def Packed : DiagGroup<"packed">;
def Padded : DiagGroup<"padded">;
+def PessimizingMove : DiagGroup<"pessimizing-move">;
def PointerArith : DiagGroup<"pointer-arith">;
def PoundWarning : DiagGroup<"#warnings">;
def PoundPragmaMessage : DiagGroup<"#pragma-messages">,
@@ -294,6 +295,7 @@ def : DiagGroup<"pointer-to-int-cast">;
def : DiagGroup<"redundant-decls">;
def RedeclaredClassMember : DiagGroup<"redeclared-class-member">;
def GNURedeclaredEnum : DiagGroup<"gnu-redeclared-enum">;
+def RedundantMove : DiagGroup<"redundant-move">;
def ReturnStackAddress : DiagGroup<"return-stack-address">;
def ReturnTypeCLinkage : DiagGroup<"return-type-c-linkage">;
def ReturnType : DiagGroup<"return-type", [ReturnTypeCLinkage]>;
Modified: cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td?rev=236075&r1=236074&r2=236075&view=diff
==============================================================================
--- cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td (original)
+++ cfe/trunk/include/clang/Basic/DiagnosticSemaKinds.td Tue Apr 28 20:52:17 2015
@@ -4777,6 +4777,17 @@ def warn_self_move : Warning<
"explicitly moving variable of type %0 to itself">,
InGroup<SelfMove>, DefaultIgnore;
+def warn_redundant_move_on_return : Warning<
+ "redundant move in return statement">,
+ InGroup<RedundantMove>, DefaultIgnore;
+def warn_pessimizing_move_on_return : Warning<
+ "moving a local object in a return statement prevents copy elision">,
+ InGroup<PessimizingMove>, DefaultIgnore;
+def warn_pessimizing_move_on_initialization : Warning<
+ "moving a temporary object prevents copy elision">,
+ InGroup<PessimizingMove>, DefaultIgnore;
+def note_remove_move : Note<"remove std::move call here">;
+
def warn_string_plus_int : Warning<
"adding %0 to a string does not append to the string">,
InGroup<StringPlusInt>;
Modified: cfe/trunk/lib/Sema/SemaInit.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=236075&r1=236074&r2=236075&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaInit.cpp (original)
+++ cfe/trunk/lib/Sema/SemaInit.cpp Tue Apr 28 20:52:17 2015
@@ -5768,6 +5768,112 @@ static void DiagnoseNarrowingInInitList(
QualType EntityType,
const Expr *PostInit);
+/// Provide warnings when std::move is used on construction.
+static void CheckMoveOnConstruction(Sema &S, const Expr *InitExpr,
+ bool IsReturnStmt) {
+ if (!InitExpr)
+ return;
+
+ QualType DestType = InitExpr->getType();
+ if (!DestType->isRecordType())
+ return;
+
+ unsigned DiagID = 0;
+ if (IsReturnStmt) {
+ const CXXConstructExpr *CCE =
+ dyn_cast<CXXConstructExpr>(InitExpr->IgnoreParens());
+ if (!CCE || CCE->getNumArgs() != 1)
+ return;
+
+ if (!CCE->getConstructor()->isCopyOrMoveConstructor())
+ return;
+
+ InitExpr = CCE->getArg(0)->IgnoreImpCasts();
+
+ // Remove implicit temporary and constructor nodes.
+ if (const MaterializeTemporaryExpr *MTE =
+ dyn_cast<MaterializeTemporaryExpr>(InitExpr)) {
+ InitExpr = MTE->GetTemporaryExpr()->IgnoreImpCasts();
+ while (const CXXConstructExpr *CCE =
+ dyn_cast<CXXConstructExpr>(InitExpr)) {
+ if (isa<CXXTemporaryObjectExpr>(CCE))
+ return;
+ if (CCE->getNumArgs() == 0)
+ return;
+ if (CCE->getNumArgs() > 1 && !isa<CXXDefaultArgExpr>(CCE->getArg(1)))
+ return;
+ InitExpr = CCE->getArg(0);
+ }
+ InitExpr = InitExpr->IgnoreImpCasts();
+ DiagID = diag::warn_redundant_move_on_return;
+ }
+ }
+
+ // Find the std::move call and get the argument.
+ const CallExpr *CE = dyn_cast<CallExpr>(InitExpr->IgnoreParens());
+ if (!CE || CE->getNumArgs() != 1)
+ return;
+
+ const FunctionDecl *MoveFunction = CE->getDirectCallee();
+ if (!MoveFunction || !MoveFunction->isInStdNamespace() ||
+ !MoveFunction->getIdentifier() ||
+ !MoveFunction->getIdentifier()->isStr("move"))
+ return;
+
+ const Expr *Arg = CE->getArg(0)->IgnoreImplicit();
+
+ if (IsReturnStmt) {
+ const DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(Arg->IgnoreParenImpCasts());
+ if (!DRE || DRE->refersToEnclosingVariableOrCapture())
+ return;
+
+ const VarDecl *VD = dyn_cast<VarDecl>(DRE->getDecl());
+ if (!VD || !VD->hasLocalStorage())
+ return;
+
+ if (DiagID == 0) {
+ DiagID = S.Context.hasSameUnqualifiedType(DestType, VD->getType())
+ ? diag::warn_pessimizing_move_on_return
+ : diag::warn_redundant_move_on_return;
+ }
+ } else {
+ DiagID = diag::warn_pessimizing_move_on_initialization;
+ const Expr *ArgStripped = Arg->IgnoreImplicit()->IgnoreParens();
+ if (!ArgStripped->isRValue() || !ArgStripped->getType()->isRecordType())
+ return;
+ }
+
+ S.Diag(CE->getLocStart(), DiagID);
+
+ // Get all the locations for a fix-it. Don't emit the fix-it if any location
+ // is within a macro.
+ SourceLocation CallBegin = CE->getCallee()->getLocStart();
+ if (CallBegin.isMacroID())
+ return;
+ SourceLocation RParen = CE->getRParenLoc();
+ if (RParen.isMacroID())
+ return;
+ SourceLocation LParen;
+ SourceLocation ArgLoc = Arg->getLocStart();
+
+ // Special testing for the argument location. Since the fix-it needs the
+ // location right before the argument, the argument location can be in a
+ // macro only if it is at the beginning of the macro.
+ while (ArgLoc.isMacroID() &&
+ S.getSourceManager().isAtStartOfImmediateMacroExpansion(ArgLoc)) {
+ ArgLoc = S.getSourceManager().getImmediateExpansionRange(ArgLoc).first;
+ }
+
+ if (LParen.isMacroID())
+ return;
+
+ LParen = ArgLoc.getLocWithOffset(-1);
+
+ S.Diag(CE->getLocStart(), diag::note_remove_move)
+ << FixItHint::CreateRemoval(SourceRange(CallBegin, LParen))
+ << FixItHint::CreateRemoval(SourceRange(RParen, RParen));
+}
+
ExprResult
InitializationSequence::Perform(Sema &S,
const InitializedEntity &Entity,
@@ -6497,6 +6603,12 @@ InitializationSequence::Perform(Sema &S,
cast<FieldDecl>(Entity.getDecl()),
CurInit.get());
+ // Check for std::move on construction.
+ if (const Expr *E = CurInit.get()) {
+ CheckMoveOnConstruction(S, E,
+ Entity.getKind() == InitializedEntity::EK_Result);
+ }
+
return CurInit;
}
Added: cfe/trunk/test/SemaCXX/warn-pessmizing-move.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-pessmizing-move.cpp?rev=236075&view=auto
==============================================================================
--- cfe/trunk/test/SemaCXX/warn-pessmizing-move.cpp (added)
+++ cfe/trunk/test/SemaCXX/warn-pessmizing-move.cpp Tue Apr 28 20:52:17 2015
@@ -0,0 +1,203 @@
+// RUN: %clang_cc1 -fsyntax-only -Wpessimizing-move -std=c++11 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wpessimizing-move -std=c++11 -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+
+// definitions for std::move
+namespace std {
+inline namespace foo {
+template <class T> struct remove_reference { typedef T type; };
+template <class T> struct remove_reference<T&> { typedef T type; };
+template <class T> struct remove_reference<T&&> { typedef T type; };
+
+template <class T> typename remove_reference<T>::type &&move(T &&t);
+}
+}
+
+struct A {};
+struct B {
+ B() {}
+ B(A) {}
+};
+
+A test1(A a1) {
+ A a2;
+ return a1;
+ return a2;
+ return std::move(a1);
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move(a2);
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+}
+
+B test2(A a1, B b1) {
+ // Object is different than return type so don't warn.
+ A a2;
+ return a1;
+ return a2;
+ return std::move(a1);
+ return std::move(a2);
+
+ B b2;
+ return b1;
+ return b2;
+ return std::move(b1);
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move(b2);
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+}
+
+A global_a;
+A test3() {
+ // Don't warn when object is not local.
+ return global_a;
+ return std::move(global_a);
+ static A static_a;
+ return static_a;
+ return std::move(static_a);
+
+}
+
+A test4() {
+ return A();
+ return test3();
+
+ return std::move(A());
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
+ return std::move(test3());
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:27-[[@LINE-4]]:28}:""
+}
+
+void test5(A) {
+ test5(A());
+ test5(test4());
+
+ test5(std::move(A()));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:9-[[@LINE-3]]:19}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ test5(std::move(test4()));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:9-[[@LINE-3]]:19}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:26-[[@LINE-4]]:27}:""
+}
+
+void test6() {
+ A a1 = A();
+ A a2 = test3();
+
+ A a3 = std::move(A());
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
+ A a4 = std::move(test3());
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:27-[[@LINE-4]]:28}:""
+}
+
+A test7() {
+ A a1 = std::move(A());
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
+ A a2 = std::move((A()));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:25-[[@LINE-4]]:26}:""
+ A a3 = (std::move(A()));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:24-[[@LINE-4]]:25}:""
+ A a4 = (std::move((A())));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:26-[[@LINE-4]]:27}:""
+
+ return std::move(a1);
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move((a1));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:24-[[@LINE-4]]:25}:""
+ return (std::move(a1));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:23-[[@LINE-4]]:24}:""
+ return (std::move((a1)));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:11-[[@LINE-3]]:21}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:25-[[@LINE-4]]:26}:""
+}
+
+#define wrap1(x) x
+#define wrap2(x) x
+
+// Macro test. Since the std::move call is outside the macro, it is
+// safe to suggest a fix-it.
+A test8(A a) {
+ return std::move(a);
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:21-[[@LINE-4]]:22}:""
+ return std::move(wrap1(a));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:28-[[@LINE-4]]:29}:""
+ return std::move(wrap1(wrap2(a)));
+ // expected-warning at -1{{prevents copy elision}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:35-[[@LINE-4]]:36}:""
+}
+
+#define test9 \
+ A test9(A a) { \
+ return std::move(a); \
+ }
+
+// Macro test. The std::call is inside the macro, so no fix-it is suggested.
+test9
+// expected-warning at -1{{prevents copy elision}}
+// CHECK-NOT: fix-it
+
+#define return_a return std::move(a)
+
+// Macro test. The std::call is inside the macro, so no fix-it is suggested.
+A test10(A a) {
+ return_a;
+ // expected-warning at -1{{prevents copy elision}}
+ // CHECK-NOT: fix-it
+}
Added: cfe/trunk/test/SemaCXX/warn-redundant-move.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/SemaCXX/warn-redundant-move.cpp?rev=236075&view=auto
==============================================================================
--- cfe/trunk/test/SemaCXX/warn-redundant-move.cpp (added)
+++ cfe/trunk/test/SemaCXX/warn-redundant-move.cpp Tue Apr 28 20:52:17 2015
@@ -0,0 +1,68 @@
+// RUN: %clang_cc1 -fsyntax-only -Wredundant-move -std=c++11 -verify %s
+// RUN: %clang_cc1 -fsyntax-only -Wredundant-move -std=c++11 -fdiagnostics-parseable-fixits %s 2>&1 | FileCheck %s
+
+// definitions for std::move
+namespace std {
+inline namespace foo {
+template <class T> struct remove_reference { typedef T type; };
+template <class T> struct remove_reference<T&> { typedef T type; };
+template <class T> struct remove_reference<T&&> { typedef T type; };
+
+template <class T> typename remove_reference<T>::type &&move(T &&t);
+}
+}
+
+struct A {};
+struct B : public A {};
+
+A test1(B b1) {
+ B b2;
+ //return b1;
+ //return b2;
+ return std::move(b1);
+ // expected-warning at -1{{redundant move}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move(b2);
+ // expected-warning at -1{{redundant move}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+}
+
+struct C {
+ C() {}
+ C(A) {}
+};
+
+C test2(A a1, B b1) {
+ A a2;
+ B b2;
+
+ return a1;
+ return a2;
+ return b1;
+ return b2;
+
+ return std::move(a1);
+ // expected-warning at -1{{redundant move}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move(a2);
+ // expected-warning at -1{{redundant move}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move(b1);
+ // expected-warning at -1{{redundant move}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+ return std::move(b2);
+ // expected-warning at -1{{redundant move}}
+ // expected-note at -2{{remove std::move call}}
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-3]]:10-[[@LINE-3]]:20}:""
+ // CHECK: fix-it:"{{.*}}":{[[@LINE-4]]:22-[[@LINE-4]]:23}:""
+}
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