From: Richard Smith <richard-llvm@metafoo.co.uk>
Date: Mon, 3 Jun 2013 07:13:35 +0000 (+0000)
Subject: Do not walk through member-accesses on bitfields when looking for the object
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=d1b55dcf6bd61d4350b01e15590bde9bb5a334bb;p=clang

Do not walk through member-accesses on bitfields when looking for the object
which is lifetime-extended by a reference binding. An additional temporary is
created for such a bitfield access (although we have no explicit AST
representation for it).


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@183095 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 2a9b9eb453..db4269bf16 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -76,9 +76,11 @@ const Expr *Expr::skipRValueSubobjectAdjustments(
       if (!ME->isArrow() && ME->getBase()->isRValue()) {
         assert(ME->getBase()->getType()->isRecordType());
         if (FieldDecl *Field = dyn_cast<FieldDecl>(ME->getMemberDecl())) {
-          E = ME->getBase();
-          Adjustments.push_back(SubobjectAdjustment(Field));
-          continue;
+          if (!Field->isBitField()) {
+            E = ME->getBase();
+            Adjustments.push_back(SubobjectAdjustment(Field));
+            continue;
+          }
         }
       }
     } else if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
diff --git a/test/CodeGenCXX/temporaries.cpp b/test/CodeGenCXX/temporaries.cpp
index ea87e7f8e3..c2adf90ac4 100644
--- a/test/CodeGenCXX/temporaries.cpp
+++ b/test/CodeGenCXX/temporaries.cpp
@@ -604,3 +604,15 @@ namespace BindToSubobject {
   // CHECK: store i32* {{.*}}, i32** @_ZN15BindToSubobject1dE, align 8
   int &&d = (B().a).*h();
 }
+
+namespace Bitfield {
+  struct S { int a : 5; ~S(); };
+
+  // Do not lifetime extend the S() temporary here.
+  // CHECK: alloca
+  // CHECK: call {{.*}}memset
+  // CHECK: store i32 {{.*}}, i32* @_ZGRN8Bitfield1rE, align 4
+  // CHECK: call void @_ZN8Bitfield1SD1
+  // CHECK: store i32* @_ZGRN8Bitfield1rE, i32** @_ZN8Bitfield1rE, align 8
+  int &&r = S().a;
+}