Completely reimplement __builtin_offsetof, based on a patch by Roberto

Amadini.

This change introduces a new expression node type, OffsetOfExpr, that
describes __builtin_offsetof. Previously, __builtin_offsetof was
implemented using a unary operator whose subexpression involved
various synthesized array-subscript and member-reference expressions,
which was ugly and made it very hard to instantiate as a
template. OffsetOfExpr represents the AST more faithfully, with proper
type source information and a more compact representation.

OffsetOfExpr also has support for dependent __builtin_offsetof
expressions; it can be value-dependent, but will never be
type-dependent (like sizeof or alignof). This commit introduces
template instantiation for __builtin_offsetof as well.

There are two major caveats to this patch:

  1) CodeGen cannot handle the case where __builtin_offsetof is not a
  constant expression, so it produces an error. So, to avoid
  regressing in C, we retain the old UnaryOperator-based
  __builtin_offsetof implementation in C while using the shiny new
  OffsetOfExpr implementation in C++. The old implementation can go
  away once we have proper CodeGen support for this case, which we
  expect won't cause much trouble in C++.

  2) __builtin_offsetof doesn't work well with non-POD class types,
  particularly when the designated field is found within a base
  class. I will address this in a subsequent patch.

Fixes PR5880 and a bunch of assertions when building Boost.Python
tests. 



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@102542 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 32 insertions, 0 deletions

diff --git a/lib/Frontend/PCHWriterStmt.cpp b/lib/Frontend/PCHWriterStmt.cpp
index a0ea5c9553..3d158a48de 100644
--- a/lib/Frontend/PCHWriterStmt.cpp
+++ b/lib/Frontend/PCHWriterStmt.cpp
@@ -62,6 +62,7 @@ namespace {
     void VisitCharacterLiteral(CharacterLiteral *E);
     void VisitParenExpr(ParenExpr *E);
     void VisitUnaryOperator(UnaryOperator *E);
+    void VisitOffsetOfExpr(OffsetOfExpr *E);
     void VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E);
     void VisitArraySubscriptExpr(ArraySubscriptExpr *E);
     void VisitCallExpr(CallExpr *E);
@@ -393,6 +394,37 @@ void PCHStmtWriter::VisitUnaryOperator(UnaryOperator *E) {
   Code = pch::EXPR_UNARY_OPERATOR;
 }
 
+void PCHStmtWriter::VisitOffsetOfExpr(OffsetOfExpr *E) {
+  VisitExpr(E);
+  Record.push_back(E->getNumComponents());
+  Record.push_back(E->getNumExpressions());
+  Writer.AddSourceLocation(E->getOperatorLoc(), Record);
+  Writer.AddSourceLocation(E->getRParenLoc(), Record);
+  Writer.AddTypeSourceInfo(E->getTypeSourceInfo(), Record);
+  for (unsigned I = 0, N = E->getNumComponents(); I != N; ++I) {
+    const OffsetOfExpr::OffsetOfNode &ON = E->getComponent(I);
+    Record.push_back(ON.getKind()); // FIXME: Stable encoding
+    Writer.AddSourceLocation(ON.getRange().getBegin(), Record);
+    Writer.AddSourceLocation(ON.getRange().getEnd(), Record);
+    switch (ON.getKind()) {
+    case OffsetOfExpr::OffsetOfNode::Array:
+      Record.push_back(ON.getArrayExprIndex());
+      break;
+        
+    case OffsetOfExpr::OffsetOfNode::Field:
+      Writer.AddDeclRef(ON.getField(), Record);
+      break;
+        
+    case OffsetOfExpr::OffsetOfNode::Identifier:
+      Writer.AddIdentifierRef(ON.getFieldName(), Record);
+      break;
+    }
+  }
+  for (unsigned I = 0, N = E->getNumExpressions(); I != N; ++I)
+    Writer.WriteSubStmt(E->getIndexExpr(I));
+  Code = pch::EXPR_OFFSETOF;
+}
+
 void PCHStmtWriter::VisitSizeOfAlignOfExpr(SizeOfAlignOfExpr *E) {
   VisitExpr(E);
   Record.push_back(E->isSizeOf());