CodeGen: Use PLT relocations for relative references to unnamed_addr functions.
The relative vtable ABI (PR26723) needs PLT relocations to refer to virtual
functions defined in other DSOs. The unnamed_addr attribute means that the
function's address is not significant, so we're allowed to substitute it
with the address of a PLT entry.
Also includes a bonus feature: addends for COFF image-relative references.
Differential Revision: http://reviews.llvm.org/D17938
llvm-svn: 267211
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index 4229741..a462655 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -438,6 +438,27 @@
KeySym);
}
+const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
+ const GlobalValue *LHS, const GlobalValue *RHS, Mangler &Mang,
+ const TargetMachine &TM) const {
+ // We may only use a PLT-relative relocation to refer to unnamed_addr
+ // functions.
+ if (!LHS->hasUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
+ return nullptr;
+
+ // Basic sanity checks.
+ if (LHS->getType()->getPointerAddressSpace() != 0 ||
+ RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
+ RHS->isThreadLocal())
+ return nullptr;
+
+ return MCBinaryExpr::createSub(
+ MCSymbolRefExpr::create(TM.getSymbol(LHS, Mang), PLTRelativeVariantKind,
+ getContext()),
+ MCSymbolRefExpr::create(TM.getSymbol(RHS, Mang), getContext()),
+ getContext());
+}
+
void
TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
UseInitArray = UseInitArray_;