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PR12208: Under -fno-elide-constructors, don't forget to actually copy an NRVO 

variable to the return slot. Patch by David Wiberg, with test case alterations
by me.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@198991 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Richard Smith 2014-01-11 01:24:05 +00:00
parent c3a5420a77
commit daffa2c523
2 changed files with 37 additions and 1 deletions
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3
lib/CodeGen/CGStmt.cpp
View File

@ -871,7 +871,8 @@ void CodeGenFunction::EmitReturnStmt(const ReturnStmt &S) {
// FIXME: Clean this up by using an LValue for ReturnTemp,
// EmitStoreThroughLValue, and EmitAnyExpr.
if (S.getNRVOCandidate() && S.getNRVOCandidate()->isNRVOVariable()) {
if (getLangOpts().ElideConstructors &&
S.getNRVOCandidate() && S.getNRVOCandidate()->isNRVOVariable()) {
// Apply the named return value optimization for this return statement,
// which means doing nothing: the appropriate result has already been
// constructed into the NRVO variable.

35
test/CodeGenCXX/no-elide-constructors.cpp Normal file
View File

@ -0,0 +1,35 @@
// RUN: %clang_cc1 -std=c++98 -triple i386-unknown-unknown -fno-elide-constructors -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX98
// RUN: %clang_cc1 -std=c++11 -triple i386-unknown-unknown -fno-elide-constructors -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX11
// RUN: %clang_cc1 -std=c++98 -triple i386-unknown-unknown -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX98-ELIDE
// RUN: %clang_cc1 -std=c++11 -triple i386-unknown-unknown -emit-llvm -o - %s | FileCheck %s --check-prefix=CHECK --check-prefix=CHECK-CXX11-ELIDE
// Reduced from PR12208
class X {
public:
X();
X(const X&);
#if __cplusplus >= 201103L
X(X&&);
#endif
~X();
};
// CHECK-LABEL: define void @_Z4Testv(
X Test()
{
X x;
// Check that the copy constructor for X is called with result variable as
// sret argument.
// CHECK-CXX98: call void @_ZN1XC1ERKS_(
// CHECK-CXX11: call void @_ZN1XC1EOS_(
// CHECK-CXX98-ELIDE-NOT: call void @_ZN1XC1ERKS_(
// CHECK-CXX11-ELIDE-NOT: call void @_ZN1XC1EOS_(
// Make sure that the destructor for X is called.
// FIXME: This call is present even in the -ELIDE runs, but is guarded by a
// branch that is never taken in those cases. We could generate better IR
// here.
// CHECK: call void @_ZN1XD1Ev(
return x;
}