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, 64 insertions, 3 deletions

diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index 8770bfd3aa..308f6b4dc0 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -549,6 +549,57 @@ QualType CallExpr::getCallReturnType() const {
   return FnType->getResultType();
 }
 
+OffsetOfExpr *OffsetOfExpr::Create(ASTContext &C, QualType type, 
+                                   SourceLocation OperatorLoc,
+                                   TypeSourceInfo *tsi, 
+                                   OffsetOfNode* compsPtr, unsigned numComps, 
+                                   Expr** exprsPtr, unsigned numExprs,
+                                   SourceLocation RParenLoc) {
+  void *Mem = C.Allocate(sizeof(OffsetOfExpr) +
+                         sizeof(OffsetOfNode) * numComps + 
+                         sizeof(Expr*) * numExprs);
+
+  return new (Mem) OffsetOfExpr(C, type, OperatorLoc, tsi, compsPtr, numComps,
+                                exprsPtr, numExprs, RParenLoc);
+}
+
+OffsetOfExpr *OffsetOfExpr::CreateEmpty(ASTContext &C,
+                                        unsigned numComps, unsigned numExprs) {
+  void *Mem = C.Allocate(sizeof(OffsetOfExpr) +
+                         sizeof(OffsetOfNode) * numComps +
+                         sizeof(Expr*) * numExprs);
+  return new (Mem) OffsetOfExpr(numComps, numExprs);
+}
+
+OffsetOfExpr::OffsetOfExpr(ASTContext &C, QualType type, 
+                           SourceLocation OperatorLoc, TypeSourceInfo *tsi,
+                           OffsetOfNode* compsPtr, unsigned numComps, 
+                           Expr** exprsPtr, unsigned numExprs,
+                           SourceLocation RParenLoc)
+  : Expr(OffsetOfExprClass, type, /*TypeDependent=*/false, 
+         /*ValueDependent=*/tsi->getType()->isDependentType() ||
+         hasAnyTypeDependentArguments(exprsPtr, numExprs) ||
+         hasAnyValueDependentArguments(exprsPtr, numExprs)),
+    OperatorLoc(OperatorLoc), RParenLoc(RParenLoc), TSInfo(tsi), 
+    NumComps(numComps), NumExprs(numExprs) 
+{
+  for(unsigned i = 0; i < numComps; ++i) {
+    setComponent(i, compsPtr[i]);
+  }
+  
+  for(unsigned i = 0; i < numExprs; ++i) {
+    setIndexExpr(i, exprsPtr[i]);
+  }
+}
+
+IdentifierInfo *OffsetOfExpr::OffsetOfNode::getFieldName() const {
+  assert(getKind() == Field || getKind() == Identifier);
+  if (getKind() == Field)
+    return getField()->getIdentifier();
+  
+  return reinterpret_cast<IdentifierInfo *> (Data & ~(uintptr_t)Mask);
+}
+
 MemberExpr *MemberExpr::Create(ASTContext &C, Expr *base, bool isarrow,
                                NestedNameSpecifier *qual,
                                SourceRange qualrange,
@@ -1891,7 +1942,7 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
     case UnaryOperator::AddrOf:
     case UnaryOperator::Deref:
       return ICEDiag(2, E->getLocStart());
-
+    case UnaryOperator::OffsetOf:
     case UnaryOperator::Extension:
     case UnaryOperator::LNot:
     case UnaryOperator::Plus:
@@ -1900,7 +1951,9 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
     case UnaryOperator::Real:
     case UnaryOperator::Imag:
       return CheckICE(Exp->getSubExpr(), Ctx);
-    case UnaryOperator::OffsetOf:
+    }
+  }
+  case Expr::OffsetOfExprClass: {
       // Note that per C99, offsetof must be an ICE. And AFAIK, using
       // Evaluate matches the proposed gcc behavior for cases like
       // "offsetof(struct s{int x[4];}, x[!.0])".  This doesn't affect
@@ -1908,7 +1961,6 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
       // array subscripts that aren't ICEs, and if the array subscripts
       // are ICEs, the value of the offsetof must be an integer constant.
       return CheckEvalInICE(E, Ctx);
-    }
   }
   case Expr::SizeOfAlignOfExprClass: {
     const SizeOfAlignOfExpr *Exp = cast<SizeOfAlignOfExpr>(E);
@@ -2702,6 +2754,15 @@ Stmt::child_iterator ParenExpr::child_end() { return &Val+1; }
 Stmt::child_iterator UnaryOperator::child_begin() { return &Val; }
 Stmt::child_iterator UnaryOperator::child_end() { return &Val+1; }
 
+// OffsetOfExpr
+Stmt::child_iterator OffsetOfExpr::child_begin() {
+  return reinterpret_cast<Stmt **> (reinterpret_cast<OffsetOfNode *> (this + 1)
+                                      + NumComps);
+}
+Stmt::child_iterator OffsetOfExpr::child_end() {
+  return child_iterator(&*child_begin() + NumExprs);
+}
+
 // SizeOfAlignOfExpr
 Stmt::child_iterator SizeOfAlignOfExpr::child_begin() {
   // If this is of a type and the type is a VLA type (and not a typedef), the