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/AsmPrinter/AsmPrinter.cpp b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
index bff2284..9ddf20b 100644
--- a/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
+++ b/llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp
@@ -1763,10 +1763,6 @@
llvm_unreachable("Unknown constant value to lower!");
}
- if (const MCExpr *RelocExpr
- = getObjFileLowering().getExecutableRelativeSymbol(CE, *Mang, TM))
- return RelocExpr;
-
switch (CE->getOpcode()) {
default:
// If the code isn't optimized, there may be outstanding folding
@@ -1842,10 +1838,34 @@
return MCBinaryExpr::createAnd(OpExpr, MaskExpr, Ctx);
}
+ case Instruction::Sub: {
+ GlobalValue *LHSGV;
+ APInt LHSOffset;
+ if (IsConstantOffsetFromGlobal(CE->getOperand(0), LHSGV, LHSOffset,
+ getDataLayout())) {
+ GlobalValue *RHSGV;
+ APInt RHSOffset;
+ if (IsConstantOffsetFromGlobal(CE->getOperand(1), RHSGV, RHSOffset,
+ getDataLayout())) {
+ const MCExpr *RelocExpr = getObjFileLowering().lowerRelativeReference(
+ LHSGV, RHSGV, *Mang, TM);
+ if (!RelocExpr)
+ RelocExpr = MCBinaryExpr::createSub(
+ MCSymbolRefExpr::create(getSymbol(LHSGV), Ctx),
+ MCSymbolRefExpr::create(getSymbol(RHSGV), Ctx), Ctx);
+ int64_t Addend = (LHSOffset - RHSOffset).getSExtValue();
+ if (Addend != 0)
+ RelocExpr = MCBinaryExpr::createAdd(
+ RelocExpr, MCConstantExpr::create(Addend, Ctx), Ctx);
+ return RelocExpr;
+ }
+ }
+ }
+ // else fallthrough
+
// The MC library also has a right-shift operator, but it isn't consistently
// signed or unsigned between different targets.
case Instruction::Add:
- case Instruction::Sub:
case Instruction::Mul:
case Instruction::SDiv:
case Instruction::SRem: