3 files changed, 39 insertions, 0 deletions
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h b/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h
index 99fa157a3ec..3dfc9ee66c2 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h
@@ -111,6 +111,11 @@ public:
   /// pseudo lowering.
   bool lowerOperand(const MachineOperand &MO, MCOperand &MCOp) const;
 
+  /// \brief Lower the specified LLVM Constant to an MCExpr.
+  /// The AsmPrinter::lowerConstantof does not know how to lower
+  /// addrspacecast, therefore they should be lowered by this function.
+  const MCExpr *lowerConstant(const Constant *CV) override;
+
   /// \brief tblgen'erated driver function for lowering simple MI->MC pseudo
   /// instructions.
   bool emitPseudoExpansionLowering(MCStreamer &OutStreamer,
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUMCInstLower.cpp b/llvm/lib/Target/AMDGPU/AMDGPUMCInstLower.cpp
index 140fd4fc988..9823fe4ff02 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUMCInstLower.cpp
+++ b/llvm/lib/Target/AMDGPU/AMDGPUMCInstLower.cpp
@@ -151,6 +151,28 @@ bool AMDGPUAsmPrinter::lowerOperand(const MachineOperand &MO,
   return MCInstLowering.lowerOperand(MO, MCOp);
 }
 
+const MCExpr *AMDGPUAsmPrinter::lowerConstant(const Constant *CV) {
+  // TargetMachine does not support llvm-style cast. Use C++-style cast.
+  // This is safe since TM is always of type AMDGPUTargetMachine or its
+  // derived class.
+  auto *AT = static_cast<AMDGPUTargetMachine*>(&TM);
+  auto *CE = dyn_cast<ConstantExpr>(CV);
+
+  // Lower null pointers in private and local address space.
+  // Clang generates addrspacecast for null pointers in private and local
+  // address space, which needs to be lowered.
+  if (CE && CE->getOpcode() == Instruction::AddrSpaceCast) {
+    auto Op = CE->getOperand(0);
+    auto SrcAddr = Op->getType()->getPointerAddressSpace();
+    if (Op->isNullValue() && AT->getNullPointerValue(SrcAddr) == 0) {
+      auto DstAddr = CE->getType()->getPointerAddressSpace();
+      return MCConstantExpr::create(AT->getNullPointerValue(DstAddr),
+        OutContext);
+    }
+  }
+  return AsmPrinter::lowerConstant(CV);
+}
+
 void AMDGPUAsmPrinter::EmitInstruction(const MachineInstr *MI) {
   if (emitPseudoExpansionLowering(*OutStreamer, MI))
     return;
diff --git a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.h b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.h
index e6981943f49..bf0b9543b89 100644
--- a/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.h
+++ b/llvm/lib/Target/AMDGPU/AMDGPUTargetMachine.h
@@ -59,6 +59,18 @@ public:
   }
 
   void adjustPassManager(PassManagerBuilder &) override;
+  /// Get the integer value of a null pointer in the given address space.
+  uint64_t getNullPointerValue(unsigned AddrSpace) const {
+    switch(AddrSpace) {
+    case AMDGPUAS::PRIVATE_ADDRESS:
+    case AMDGPUAS::LOCAL_ADDRESS:
+    case AMDGPUAS::REGION_ADDRESS:
+      return -1;
+    default:
+      return 0;
+    }
+  }
+
 };
 
 //===----------------------------------------------------------------------===//