Teach sema and codegen about the difference between address of labels,
which is a common idiom to improve PIC'ness of code using the addr of
label extension. This implementation is a gross hack, but the only other
alternative would be to teach evalutate about this horrid combination.
While GCC allows things like "&&foo - &&bar + 1", people don't use this
in practice. This implements PR5131.
git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@83957 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGExprConstant.cpp b/lib/CodeGen/CGExprConstant.cpp
index fc24144..9621e2a 100644
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@@ -402,7 +402,7 @@
llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
return Visit(E->getInitializer());
}
-
+
llvm::Constant *EmitMemberFunctionPointer(CXXMethodDecl *MD) {
assert(MD->isInstance() && "Member function must not be static!");
@@ -446,6 +446,27 @@
return 0;
}
+ llvm::Constant *VisitBinSub(BinaryOperator *E) {
+ // This must be a pointer/pointer subtraction. This only happens for
+ // address of label.
+ if (!isa<AddrLabelExpr>(E->getLHS()->IgnoreParenNoopCasts(CGM.getContext())) ||
+ !isa<AddrLabelExpr>(E->getRHS()->IgnoreParenNoopCasts(CGM.getContext())))
+ return 0;
+
+ llvm::Constant *LHS = CGM.EmitConstantExpr(E->getLHS(),
+ E->getLHS()->getType(), CGF);
+ llvm::Constant *RHS = CGM.EmitConstantExpr(E->getRHS(),
+ E->getRHS()->getType(), CGF);
+
+ const llvm::Type *ResultType = ConvertType(E->getType());
+ LHS = llvm::ConstantExpr::getPtrToInt(LHS, ResultType);
+ RHS = llvm::ConstantExpr::getPtrToInt(RHS, ResultType);
+
+ // No need to divide by element size, since addr of label is always void*,
+ // which has size 1 in GNUish.
+ return llvm::ConstantExpr::getSub(LHS, RHS);
+ }
+
llvm::Constant *VisitCastExpr(CastExpr* E) {
switch (E->getCastKind()) {
case CastExpr::CK_ToUnion: {