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

2 files changed, 10 insertions, 1 deletions

diff --git a/include/clang/Frontend/PCHBitCodes.h b/include/clang/Frontend/PCHBitCodes.h
index 457e63332f..1640afb412 100644
--- a/include/clang/Frontend/PCHBitCodes.h
+++ b/include/clang/Frontend/PCHBitCodes.h
@@ -603,6 +603,8 @@ namespace clang {
       EXPR_PAREN,
       /// \brief A UnaryOperator record.
       EXPR_UNARY_OPERATOR,
+      /// \brief An OffsetOfExpr record.
+      EXPR_OFFSETOF,
       /// \brief A SizefAlignOfExpr record.
       EXPR_SIZEOF_ALIGN_OF,
       /// \brief An ArraySubscriptExpr record.
diff --git a/include/clang/Frontend/StmtXML.def b/include/clang/Frontend/StmtXML.def
index 2f0da9e7b1..f63761a908 100644
--- a/include/clang/Frontend/StmtXML.def
+++ b/include/clang/Frontend/StmtXML.def
@@ -254,7 +254,7 @@ NODE_XML(UnaryOperator, "UnaryOperator")                // op(expr) or (expr)op
     ENUM_XML(UnaryOperator::Real,    "__real")
     ENUM_XML(UnaryOperator::Imag,    "__imag")
     ENUM_XML(UnaryOperator::Extension, "__extension__")
-    ENUM_XML(UnaryOperator::OffsetOf,  "__builtin_offsetof")
+    ENUM_XML(UnaryOperator::OffsetOf, "__builtin_offsetof")
   END_ENUM_XML
   SUB_NODE_XML(Expr)                                    // expr
 END_NODE_XML
@@ -311,6 +311,13 @@ NODE_XML(ConditionalOperator, "ConditionalOperator")    // expr1 ? expr2 : expr3
   SUB_NODE_XML(Expr)                                    // expr3
 END_NODE_XML
 
+NODE_XML(OffsetOfExpr, "OffsetOfExpr")                  // offsetof(basetype, components)
+  ATTRIBUTE_FILE_LOCATION_XML
+  TYPE_ATTRIBUTE_XML(getTypeSourceInfo()->getType())
+  ATTRIBUTE_XML(getNumComponents(), "num_components")
+  SUB_NODE_SEQUENCE_XML(OffsetOfExpr::OffsetOfNode)
+END_NODE_XML
+
 NODE_XML(SizeOfAlignOfExpr, "SizeOfAlignOfExpr")        // sizeof(expr) or alignof(expr)
   ATTRIBUTE_FILE_LOCATION_XML
   TYPE_ATTRIBUTE_XML(getType())