From 8ecdb65716cd7914ffb2eeee993fa9039fcd31e8 Mon Sep 17 00:00:00 2001 From: Douglas Gregor Date: Wed, 28 Apr 2010 22:16:22 +0000 Subject: 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 --- lib/CodeGen/CGExprScalar.cpp | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) (limited to 'lib/CodeGen/CGExprScalar.cpp') diff --git a/lib/CodeGen/CGExprScalar.cpp b/lib/CodeGen/CGExprScalar.cpp index 842590b24c..9849688023 100644 --- a/lib/CodeGen/CGExprScalar.cpp +++ b/lib/CodeGen/CGExprScalar.cpp @@ -133,6 +133,7 @@ public: CGF.getContext().typesAreCompatible( E->getArgType1(), E->getArgType2())); } + Value *VisitOffsetOfExpr(const OffsetOfExpr *E); Value *VisitSizeOfAlignOfExpr(const SizeOfAlignOfExpr *E); Value *VisitAddrLabelExpr(const AddrLabelExpr *E) { llvm::Value *V = CGF.GetAddrOfLabel(E->getLabel()); @@ -242,7 +243,7 @@ public: return Visit(E->getSubExpr()); } Value *VisitUnaryOffsetOf(const UnaryOperator *E); - + // C++ Value *VisitCXXDefaultArgExpr(CXXDefaultArgExpr *DAE) { return Visit(DAE->getExpr()); @@ -1030,6 +1031,21 @@ Value *ScalarExprEmitter::VisitUnaryLNot(const UnaryOperator *E) { return Builder.CreateZExt(BoolVal, ConvertType(E->getType()), "lnot.ext"); } +Value *ScalarExprEmitter::VisitOffsetOfExpr(const OffsetOfExpr *E) { + Expr::EvalResult Result; + if(E->Evaluate(Result, CGF.getContext())) + return llvm::ConstantInt::get(VMContext, Result.Val.getInt()); + + // FIXME: Cannot support code generation for non-constant offsetof. + unsigned DiagID = CGF.CGM.getDiags().getCustomDiagID(Diagnostic::Error, + "cannot compile non-constant __builtin_offsetof"); + CGF.CGM.getDiags().Report(CGF.getContext().getFullLoc(E->getLocStart()), + DiagID) + << E->getSourceRange(); + + return llvm::Constant::getNullValue(ConvertType(E->getType())); +} + /// VisitSizeOfAlignOfExpr - Return the size or alignment of the type of /// argument of the sizeof expression as an integer. Value * -- cgit v1.2.3-70-g09d2