constexpr irgen: Add irgen support for APValue::Struct, APValue::Union,

APValue::Array and APValue::MemberPointer. All APValue values can now be emitted
as constants.

Add new CGCXXABI entry point for emitting an APValue MemberPointer. The other
entrypoints dealing with constant member pointers are no longer necessary and
will be removed in a later change.

Switch codegen from using EvaluateAsRValue/EvaluateAsLValue to
VarDecl::evaluateValue. This performs caching and deals with the nasty cases in
C++11 where a non-const object's initializer can refer indirectly to
previously-initialized fields within the same object.

Building the intermediate APValue object incurs a measurable performance hit on
pathological testcases with huge initializer lists, so we continue to build IR
directly from the Expr nodes for array and record types outside of C++11.

llvm-svn: 148178

1 files changed, 10 insertions, 5 deletions

diff --git a/clang/lib/AST/Decl.cpp b/clang/lib/AST/Decl.cpp
index 9132b0a1903..3caca9d7e6c 100644
--- a/clang/lib/AST/Decl.cpp
+++ b/clang/lib/AST/Decl.cpp
@@ -1379,15 +1379,20 @@ EvaluatedStmt *VarDecl::ensureEvaluatedStmt() const {
   return Eval;
 }
 
-bool VarDecl::evaluateValue(
-                      llvm::SmallVectorImpl<PartialDiagnosticAt> &Notes) const {
+APValue *VarDecl::evaluateValue() const {
+  llvm::SmallVector<PartialDiagnosticAt, 8> Notes;
+  return evaluateValue(Notes);
+}
+
+APValue *VarDecl::evaluateValue(
+    llvm::SmallVectorImpl<PartialDiagnosticAt> &Notes) const {
   EvaluatedStmt *Eval = ensureEvaluatedStmt();
 
   // We only produce notes indicating why an initializer is non-constant the
   // first time it is evaluated. FIXME: The notes won't always be emitted the
   // first time we try evaluation, so might not be produced at all.
   if (Eval->WasEvaluated)
-    return !Eval->Evaluated.isUninit();
+    return Eval->Evaluated.isUninit() ? 0 : &Eval->Evaluated;
 
   const Expr *Init = cast<Expr>(Eval->Value);
   assert(!Init->isValueDependent());
@@ -1396,7 +1401,7 @@ bool VarDecl::evaluateValue(
     // FIXME: Produce a diagnostic for self-initialization.
     Eval->CheckedICE = true;
     Eval->IsICE = false;
-    return false;
+    return 0;
   }
 
   Eval->IsEvaluating = true;
@@ -1418,7 +1423,7 @@ bool VarDecl::evaluateValue(
     Eval->IsICE = Notes.empty();
   }
 
-  return Result;
+  return Result ? &Eval->Evaluated : 0;
 }
 
 bool VarDecl::checkInitIsICE() const {