AMDGPU: Emit note directive for HSA even if there are no functions

[• tstellarAMD]

Spoke with echristo an IRC, and I'm going to implement this a better way.

[• tstellarAMD]

Move getISAVersion() into the TargetMachine.

[echristo]

lib/Target/AMDGPU/AMDGPUTargetMachine.h

90 ↗

(On Diff #44389)

This is pretty gross. Why not just move the variable to the TargetMachine or have a function that's part of the target machine that looks up ISA version based on... whatever it is it's based on? :)

[• tstellarAMD]

lib/Target/AMDGPU/AMDGPUTargetMachine.h

90 ↗

(On Diff #44389)

ISA version is based on the CPU string. The reason to do it this way is the logic mapping CPU strings to IsaVersion already exists in the .TD files and I didn't want to duplicate the logic here, but if implementing it this way is a problem then I can duplicate the logic here, it should be a problem. Do you have a preference?

[• tstellarAMD]

Construct an MCSubtargetInfo object in the AsmPrinter so we can fetch
the feature bits.

[echristo]

This is fine. You should probably clean up getIsaVersion. It appears to be just used as a tag in the object so it doesn't really need a subtarget feature, you could just have a static version that returns a number.

-eric

lib/Target/AMDGPU/AMDGPUAsmPrinter.h

public:
   void EmitInstruction(const MachineInstr *MI) override;
 
   void EmitFunctionBodyStart() override;
 
   void EmitFunctionEntryLabel() override;
 
   void EmitGlobalVariable(const GlobalVariable *GV) override;
 
+  void EmitStartOfAsmFile(Module &M) override;
+
   bool PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                        unsigned AsmVariant, const char *ExtraCode,
                        raw_ostream &O) override;
 
 protected:
   std::vector<std::string> DisasmLines, HexLines;
   size_t DisasmLineMaxLen;
 };
 
 } // End anonymous llvm
 
 #endif

lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp

extern "C" void LLVMInitializeAMDGPUAsmPrinter() {
   TargetRegistry::RegisterAsmPrinter(TheAMDGPUTarget, createAMDGPUAsmPrinterPass);
   TargetRegistry::RegisterAsmPrinter(TheGCNTarget, createAMDGPUAsmPrinterPass);
 }
 
 AMDGPUAsmPrinter::AMDGPUAsmPrinter(TargetMachine &TM,
                                    std::unique_ptr<MCStreamer> Streamer)
     : AsmPrinter(TM, std::move(Streamer)) {}
 
+void AMDGPUAsmPrinter::EmitStartOfAsmFile(Module &M) {
+  if (TM.getTargetTriple().getOS() != Triple::AMDHSA)
+    return;
+
+  // Need to construct an MCSubtargetInfo here in case we have no functions
+  // in the module.
+  std::unique_ptr<MCSubtargetInfo> STI(TM.getTarget().createMCSubtargetInfo(
+        TM.getTargetTriple().str(), TM.getTargetCPU(),
+        TM.getTargetFeatureString()));
+
+  AMDGPUTargetStreamer *TS =
+      static_cast<AMDGPUTargetStreamer *>(OutStreamer->getTargetStreamer());
+
+  TS->EmitDirectiveHSACodeObjectVersion(1, 0);
+  AMDGPU::IsaVersion ISA = AMDGPU::getIsaVersion(STI->getFeatureBits());
+  TS->EmitDirectiveHSACodeObjectISA(ISA.Major, ISA.Minor, ISA.Stepping,
+                                    "AMD", "AMDGPU");
+}
+
 void AMDGPUAsmPrinter::EmitFunctionBodyStart() {
   const AMDGPUSubtarget &STM = MF->getSubtarget<AMDGPUSubtarget>();
   SIProgramInfo KernelInfo;
   if (STM.isAmdHsaOS()) {
     getSIProgramInfo(KernelInfo, *MF);
     EmitAmdKernelCodeT(*MF, KernelInfo);
   }
 }
bool AMDGPUAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
 
   const AMDGPUSubtarget &STM = MF.getSubtarget<AMDGPUSubtarget>();
   SIProgramInfo KernelInfo;
   if (STM.getGeneration() >= AMDGPUSubtarget::SOUTHERN_ISLANDS) {
     getSIProgramInfo(KernelInfo, MF);
     if (!STM.isAmdHsaOS()) {
       EmitProgramInfoSI(MF, KernelInfo);
     }
-    // Emit directives
-    AMDGPUTargetStreamer *TS =
-        static_cast<AMDGPUTargetStreamer *>(OutStreamer->getTargetStreamer());
-    TS->EmitDirectiveHSACodeObjectVersion(1, 0);
-    AMDGPU::IsaVersion ISA = STM.getIsaVersion();
-    TS->EmitDirectiveHSACodeObjectISA(ISA.Major, ISA.Minor, ISA.Stepping,
-                                      "AMD", "AMDGPU");
   } else {
     EmitProgramInfoR600(MF);
   }
 
   DisasmLines.clear();
   HexLines.clear();
   DisasmLineMaxLen = 0;
 

test/CodeGen/AMDGPU/hsa-note-no-func.ll

+; RUN: llc < %s -mtriple=amdgcn--amdhsa -mcpu=kaveri | FileCheck --check-prefix=HSA --check-prefix=HSA-CI %s
+; RUN: llc < %s -mtriple=amdgcn--amdhsa -mcpu=carrizo | FileCheck --check-prefix=HSA --check-prefix=HSA-VI %s
+
+; HSA: .hsa_code_object_version 1,0
+; HSA-CI: .hsa_code_object_isa 7,0,0,"AMD","AMDGPU"
+; HSA-VI: .hsa_code_object_isa 8,0,1,"AMD","AMDGPU"