Commit 584a5639 authored by Hans Wennborg's avatar Hans Wennborg
Browse files

Merging r242600: 

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r242600 | davide | 2015-07-17 18:15:19 -0700 (Fri, 17 Jul 2015) | 8 lines

[Sema] Emit correct warning when copy-elision is not possible.

If we're returning a function parameter, copy elision isn't possible,
so we now warn for redundant move.

PR:		23819
Differential Revision:	 http://reviews.llvm.org/D11305

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llvm-svn: 243605
parent d834a191

clang/lib/Sema/SemaInit.cpp

+5 −0
Original line number Diff line number Diff line
@@ -5986,6 +5986,11 @@ static void CheckMoveOnConstruction(Sema &S, const Expr *InitExpr, 
    if (!VD->getType()->isRecordType())

      return;



    // If we're returning a function parameter, copy elision

    // is not possible.

    if (isa<ParmVarDecl>(VD))

      DiagID = diag::warn_redundant_move_on_return;



    if (DiagID == 0) {

      DiagID = S.Context.hasSameUnqualifiedType(DestType, VD->getType())

                   ? diag::warn_pessimizing_move_on_return

clang/test/SemaCXX/warn-pessmizing-move.cpp

+7 −12
Original line number Diff line number Diff line
@@ -23,10 +23,6 @@ A test1(A a1) { 
  return a1;

  return a2;

  return std::move(a1);

  // expected-warning@-1{{prevents copy elision}}

  // expected-note@-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@-1{{prevents copy elision}}

  // expected-note@-2{{remove std::move call}}
@@ -46,10 +42,6 @@ B test2(A a1, B b1) { 
  return b1;

  return b2;

  return std::move(b1);

  // expected-warning@-1{{prevents copy elision}}

  // expected-note@-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@-1{{prevents copy elision}}

  // expected-note@-2{{remove std::move call}}
@@ -165,7 +157,8 @@ A test7() { 


// Macro test. Since the std::move call is outside the macro, it is

// safe to suggest a fix-it.

A test8(A a) {

A test8() {

  A a;

  return std::move(a);

  // expected-warning@-1{{prevents copy elision}}

  // expected-note@-2{{remove std::move call}}
@@ -184,7 +177,8 @@ A test8(A a) { 
}



#define test9            \

  A test9(A a) {         \

  A test9() {            \

    A a;                 \

    return std::move(a); \

  }
@@ -196,7 +190,8 @@ test9 
#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) {

A test10() {

  A a;

  return_a;

  // expected-warning@-1{{prevents copy elision}}

  // CHECK-NOT: fix-it

clang/test/SemaCXX/warn-redundant-move.cpp

+7 −0
Original line number Diff line number Diff line
@@ -90,3 +90,10 @@ C test4(A& a1, B& b1) { 
  return std::move(b1);

  return std::move(b2);

}



//PR23819

struct X {};

X g();

void h(X&&);

X f(X x) { return std::move(x); } //expected-warning{{redundant move in return statement}} \

                                  //expected-note{{remove std::move call here}}