Model temporary lifetime-extension explicitly in the AST. Use this model to

handle temporaries which have been lifetime-extended to static storage duration
within constant expressions. This correctly handles nested lifetime extension
(through reference members of aggregates in aggregate initializers) but
non-constant-expression emission hasn't yet been updated to do the same.

llvm-svn: 183283

1 files changed, 57 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 3675e849aa7..4d64624dbcb 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -2735,6 +2735,63 @@ llvm::Constant *CodeGenModule::GetAddrOfConstantCString(const std::string &Str,
   return GetAddrOfConstantString(StrWithNull, GlobalName, Alignment);
 }
 
+llvm::Constant *CodeGenModule::GetAddrOfGlobalTemporary(
+    const MaterializeTemporaryExpr *E, const Expr *Inner) {
+  assert((E->getStorageDuration() == SD_Static ||
+          E->getStorageDuration() == SD_Thread) && "not a global temporary");
+  const VarDecl *VD = cast<VarDecl>(E->getExtendingDecl());
+
+  // If we're not materializing a subobject of the temporary, keep the
+  // cv-qualifiers from the type of the MaterializeTemporaryExpr.
+  if (Inner == E->GetTemporaryExpr())
+    Inner = E;
+
+  llvm::Constant *&Slot = MaterializedGlobalTemporaryMap[E];
+  if (Slot)
+    return Slot;
+
+  // FIXME: If an externally-visible declaration extends multiple temporaries,
+  // we need to give each temporary the same name in every translation unit (and
+  // we also need to make the temporaries externally-visible).
+  SmallString<256> Name;
+  llvm::raw_svector_ostream Out(Name);
+  getCXXABI().getMangleContext().mangleReferenceTemporary(VD, Out);
+  Out.flush();
+
+  llvm::Constant *InitialValue = 0;
+  APValue *Value = 0;
+  if (E->getStorageDuration() == SD_Static) {
+    // We might have a constant initializer for this temporary.
+    Value = getContext().getMaterializedTemporaryValue(E, false);
+    if (Value && Value->isUninit())
+      Value = 0;
+  }
+
+  bool Constant;
+  if (Value) {
+    // The temporary has a constant initializer, use it.
+    InitialValue = EmitConstantValue(*Value, Inner->getType(), 0);
+    Constant = isTypeConstant(Inner->getType(), /*ExcludeCtor*/Value);
+  } else {
+    // No constant initializer, the initialization will be provided when we
+    // initialize the declaration which performed lifetime extension.
+    InitialValue = EmitNullConstant(Inner->getType());
+    Constant = false;
+  }
+
+  // Create a global variable for this lifetime-extended temporary.
+  llvm::GlobalVariable *GV =
+    new llvm::GlobalVariable(getModule(), InitialValue->getType(), Constant,
+                             llvm::GlobalValue::PrivateLinkage, InitialValue,
+                             Name.c_str());
+  GV->setAlignment(
+      getContext().getTypeAlignInChars(Inner->getType()).getQuantity());
+  if (VD->getTLSKind())
+    setTLSMode(GV, *VD);
+  Slot = GV;
+  return GV;
+}
+
 /// EmitObjCPropertyImplementations - Emit information for synthesized
 /// properties for an implementation.
 void CodeGenModule::EmitObjCPropertyImplementations(const