3 files changed, 33 insertions, 0 deletions
diff --git a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
index eb2a28f574a..d19ca47ec1a 100644
--- a/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
+++ b/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
@@ -1055,6 +1055,13 @@ MCSection *TargetLoweringObjectFileCOFF::getSectionForJumpTable(
                                      COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
 }
 
+bool TargetLoweringObjectFileCOFF::shouldPutJumpTableInFunctionSection(
+    bool UsesLabelDifference, const Function &F) const {
+  // We can always create relative relocations, so use another section
+  // that can be marked non-executable.
+  return false;
+}
+
 void TargetLoweringObjectFileCOFF::emitModuleFlags(
     MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
     const TargetMachine &TM) const {
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
index b293dfa98f8..d0c77030acd 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.cpp
+++ b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -1926,10 +1926,20 @@ unsigned X86TargetLowering::getJumpTableEncoding() const {
   if (isPositionIndependent() && Subtarget.isPICStyleGOT())
     return MachineJumpTableInfo::EK_Custom32;
 
+  // On Win64, we want to use both label differences and a separate section.
+  if (Subtarget.isTargetWin64())
+    return MachineJumpTableInfo::EK_LabelDifference32;
+
   // Otherwise, use the normal jump table encoding heuristics.
   return TargetLowering::getJumpTableEncoding();
 }
 
+bool X86TargetLowering::isJumpTableRelative() const {
+  if (Subtarget.isTargetWin64())
+    return true;
+  return TargetLowering::isJumpTableRelative();
+}
+
 bool X86TargetLowering::useSoftFloat() const {
   return Subtarget.useSoftFloat();
 }
@@ -1948,11 +1958,19 @@ X86TargetLowering::LowerCustomJumpTableEntry(const MachineJumpTableInfo *MJTI,
 /// Returns relocation base for the given PIC jumptable.
 SDValue X86TargetLowering::getPICJumpTableRelocBase(SDValue Table,
                                                     SelectionDAG &DAG) const {
+  // COFF doesn't have relocations to take the difference between two arbitrary
+  // symbols. The assembler, however, can resolve a fixup between the function
+  // entry and a basic block label, so use the function entry as the base.
+  if (Subtarget.isTargetWin64())
+    return DAG.getGlobalAddress(DAG.getMachineFunction().getFunction(), SDLoc(),
+                                getPointerTy(DAG.getDataLayout()));
+
   if (!Subtarget.is64Bit())
     // This doesn't have SDLoc associated with it, but is not really the
     // same as a Register.
     return DAG.getNode(X86ISD::GlobalBaseReg, SDLoc(),
                        getPointerTy(DAG.getDataLayout()));
+
   return Table;
 }
 
@@ -1961,6 +1979,13 @@ SDValue X86TargetLowering::getPICJumpTableRelocBase(SDValue Table,
 const MCExpr *X86TargetLowering::
 getPICJumpTableRelocBaseExpr(const MachineFunction *MF, unsigned JTI,
                              MCContext &Ctx) const {
+  // COFF doesn't have relocations to take the difference between two arbitrary
+  // symbols. The assembler, however, can resolve a fixup between the function
+  // entry and a basic block label, so use the function entry as the base.
+  if (Subtarget.isTargetWin64())
+    return MCSymbolRefExpr::create(
+        getTargetMachine().getSymbol(MF->getFunction()), Ctx);
+
   // X86-64 uses RIP relative addressing based on the jump table label.
   if (Subtarget.isPICStyleRIPRel())
     return TargetLowering::getPICJumpTableRelocBaseExpr(MF, JTI, Ctx);
diff --git a/llvm/lib/Target/X86/X86ISelLowering.h b/llvm/lib/Target/X86/X86ISelLowering.h
index 37f9353042b..643727d7aed 100644
--- a/llvm/lib/Target/X86/X86ISelLowering.h
+++ b/llvm/lib/Target/X86/X86ISelLowering.h
@@ -684,6 +684,7 @@ namespace llvm {
                                const X86Subtarget &STI);
 
     unsigned getJumpTableEncoding() const override;
+    bool isJumpTableRelative() const override;
     bool useSoftFloat() const override;
 
     MVT getScalarShiftAmountTy(const DataLayout &, EVT) const override {