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
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index a52cf6f..7233518 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -16,7 +16,9 @@
#include "clang/AST/CharUnits.h"
#include "clang/AST/RecordLayout.h"
#include "clang/AST/StmtVisitor.h"
+#include "clang/AST/TypeLoc.h"
#include "clang/AST/ASTDiagnostic.h"
+#include "clang/AST/Expr.h"
#include "clang/Basic/Builtins.h"
#include "clang/Basic/TargetInfo.h"
#include "llvm/ADT/SmallString.h"
@@ -228,7 +230,7 @@
APValue VisitStmt(Stmt *S) {
return APValue();
}
-
+
APValue VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
APValue VisitDeclRefExpr(DeclRefExpr *E);
APValue VisitPredefinedExpr(PredefinedExpr *E) { return APValue(E); }
@@ -828,6 +830,7 @@
bool VisitCallExpr(CallExpr *E);
bool VisitBinaryOperator(const BinaryOperator *E);
+ bool VisitOffsetOfExpr(const OffsetOfExpr *E);
bool VisitUnaryOperator(const UnaryOperator *E);
bool VisitConditionalOperator(const ConditionalOperator *E);
@@ -1372,6 +1375,61 @@
return Success(Info.Ctx.getTypeSizeInChars(SrcTy).getQuantity(), E);
}
+bool IntExprEvaluator::VisitOffsetOfExpr(const OffsetOfExpr *E) {
+ CharUnits Result;
+ unsigned n = E->getNumComponents();
+ OffsetOfExpr* OOE = const_cast<OffsetOfExpr*>(E);
+ if (n == 0)
+ return false;
+ QualType CurrentType = E->getTypeSourceInfo()->getType();
+ for (unsigned i = 0; i != n; ++i) {
+ OffsetOfExpr::OffsetOfNode ON = OOE->getComponent(i);
+ switch (ON.getKind()) {
+ case OffsetOfExpr::OffsetOfNode::Array: {
+ Expr *Idx = OOE->getIndexExpr(ON.getArrayExprIndex());
+ APSInt IdxResult;
+ if (!EvaluateInteger(Idx, IdxResult, Info))
+ return false;
+ const ArrayType *AT = Info.Ctx.getAsArrayType(CurrentType);
+ if (!AT)
+ return false;
+ CurrentType = AT->getElementType();
+ CharUnits ElementSize = Info.Ctx.getTypeSizeInChars(CurrentType);
+ Result += IdxResult.getSExtValue() * ElementSize;
+ break;
+ }
+
+ case OffsetOfExpr::OffsetOfNode::Field: {
+ FieldDecl *MemberDecl = ON.getField();
+ const RecordType *RT = CurrentType->getAs<RecordType>();
+ if (!RT)
+ return false;
+ RecordDecl *RD = RT->getDecl();
+ const ASTRecordLayout &RL = Info.Ctx.getASTRecordLayout(RD);
+ unsigned i = 0;
+ // FIXME: It would be nice if we didn't have to loop here!
+ for (RecordDecl::field_iterator Field = RD->field_begin(),
+ FieldEnd = RD->field_end();
+ Field != FieldEnd; (void)++Field, ++i) {
+ if (*Field == MemberDecl)
+ break;
+ }
+ if (i < RL.getFieldCount())
+ Result += CharUnits::fromQuantity(
+ RL.getFieldOffset(i) / Info.Ctx.getCharWidth());
+ else
+ return false;
+ CurrentType = MemberDecl->getType().getNonReferenceType();
+ break;
+ }
+
+ case OffsetOfExpr::OffsetOfNode::Identifier:
+ llvm_unreachable("dependent __builtin_offsetof");
+ }
+ }
+ return Success(Result.getQuantity(), E);
+}
+
bool IntExprEvaluator::VisitUnaryOperator(const UnaryOperator *E) {
// Special case unary operators that do not need their subexpression
// evaluated. offsetof/sizeof/alignof are all special.
@@ -1380,12 +1438,12 @@
// directly Evaluate it as an l-value.
APValue LV;
if (!EvaluateLValue(E->getSubExpr(), LV, Info))
- return false;
+ return false;
if (LV.getLValueBase())
- return false;
+ return false;
return Success(LV.getLValueOffset().getQuantity(), E);
}
-
+
if (E->getOpcode() == UnaryOperator::LNot) {
// LNot's operand isn't necessarily an integer, so we handle it specially.
bool bres;