[AMDGPU] Fixed +DumpCode

[tpr]

Summary

The +DumpCode attribute is a horrible hack in AMDGPU to embed the
disassembly of the generated code into the elf file. It is used by LLPC
to implement an extension that allows the application to read back the
disassembly of the code. Longer term, we should re-implement that by
using the LLVM disassembler from the Vulkan driver.

Recent LLVM changes broke +DumpCode. With -filetype=asm it crashed, and
with -filetype=obj I think it did not include any instructions, only the
labels. Fixed with this commit: now it has no effect with -filetype=asm,
and works as intended with -filetype=obj.

Change-Id: I6436d86fe2ea220d74a643a85e64753747c9366b

[arsenm]

Do we really still need DumpCode? I've long wanted to remove it. Is there any real obstacle remaining to users switching to some combination of the assembler and disassembler?

[tpr]

I think the only obstacle is getting round to doing the LLPC changes. So this is hopefully a short term fix until we can get around to it.

[tpr]

PS I'm only speaking for LLPC. I don't know if Mesa uses it.

[nhaehnle]

Mesa uses +DumpCode as well. Do we have a good solution for generation both ELF and textual output?

[scott.linder]

In D60682#1470258, @nhaehnle wrote:

Mesa uses +DumpCode as well. Do we have a good solution for generation both ELF and textual output?

Yes, depending on what you mean by "good": just codegen to ASM, then assemble that to the ELF? One codegen gets you both the text and object without the need for the hack.

As far as the review goes, it looks like a hack to setUseAssemblerInfoForParsing here, but as long as the code behaves correctly in the cases where it is unset (seems to be just inline assembly?) then it is just a continuation of the +DumpCode hack, so it seems fine to me.

[tpr]

Ping: Could someone approve this please? Thanks.

lib/Target/AMDGPU/AMDGPUAsmPrinter.h

 #include <memory>
 #include <string>
 #include <vector>
 
 namespace llvm {
 
 class AMDGPUMachineFunction;
 class AMDGPUTargetStreamer;
+class MCCodeEmitter;
 class MCOperand;
 class GCNSubtarget;
 
 class AMDGPUAsmPrinter final : public AsmPrinter {
 private:
   // Track resource usage for callee functions.
   struct SIFunctionResourceInfo {
     // Track the number of explicitly used VGPRs. Special registers reserved at
struct SIFunctionResourceInfo {
     int32_t getTotalNumSGPRs(const GCNSubtarget &ST) const;
   };
 
   SIProgramInfo CurrentProgramInfo;
   DenseMap<const Function *, SIFunctionResourceInfo> CallGraphResourceInfo;
 
   std::unique_ptr<AMDGPU::HSAMD::MetadataStreamer> HSAMetadataStream;
 
+  MCCodeEmitter *DumpCodeInstEmitter = nullptr;
+
   uint64_t getFunctionCodeSize(const MachineFunction &MF) const;
   SIFunctionResourceInfo analyzeResourceUsage(const MachineFunction &MF) const;
 
   void getSIProgramInfo(SIProgramInfo &Out, const MachineFunction &MF);
   void getAmdKernelCode(amd_kernel_code_t &Out, const SIProgramInfo &KernelInfo,
                         const MachineFunction &MF) const;
   void findNumUsedRegistersSI(const MachineFunction &MF,
                               unsigned &NumSGPR,

lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp

 #include "SIDefines.h"
 #include "SIInstrInfo.h"
 #include "SIMachineFunctionInfo.h"
 #include "SIRegisterInfo.h"
 #include "Utils/AMDGPUBaseInfo.h"
 #include "llvm/BinaryFormat/ELF.h"
 #include "llvm/CodeGen/MachineFrameInfo.h"
 #include "llvm/IR/DiagnosticInfo.h"
+#include "llvm/MC/MCAssembler.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCSectionELF.h"
 #include "llvm/MC/MCStreamer.h"
 #include "llvm/Support/AMDGPUMetadata.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/TargetParser.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Target/TargetLoweringObjectFile.h"
if (!STM.hasCodeObjectV3() && STM.isAmdHsaOrMesa(F) &&
        F.getCallingConv() == CallingConv::SPIR_KERNEL)) {
     amd_kernel_code_t KernelCode;
     getAmdKernelCode(KernelCode, CurrentProgramInfo, *MF);
     getTargetStreamer()->EmitAMDKernelCodeT(KernelCode);
   }
 
   if (STM.isAmdHsaOS())
     HSAMetadataStream->emitKernel(*MF, CurrentProgramInfo);
+
+  DumpCodeInstEmitter = nullptr;
+  if (STM.dumpCode()) {
+    // For -dumpcode, get the assembler out of the streamer, even if it does
+    // not really want to let us have it. This only works with -filetype=obj.
+    bool SaveFlag = OutStreamer->getUseAssemblerInfoForParsing();
+    OutStreamer->setUseAssemblerInfoForParsing(true);
+    MCAssembler *Assembler = OutStreamer->getAssemblerPtr();
+    OutStreamer->setUseAssemblerInfoForParsing(SaveFlag);
+    if (Assembler)
+      DumpCodeInstEmitter = Assembler->getEmitterPtr();
+  }
 }
 
 void AMDGPUAsmPrinter::EmitFunctionBodyEnd() {
   const SIMachineFunctionInfo &MFI = *MF->getInfo<SIMachineFunctionInfo>();
   if (!MFI.isEntryFunction())
     return;
 
   if (!IsaInfo::hasCodeObjectV3(getGlobalSTI()) ||
void AMDGPUAsmPrinter::EmitFunctionEntryLabel() {
   const SIMachineFunctionInfo *MFI = MF->getInfo<SIMachineFunctionInfo>();
   const GCNSubtarget &STM = MF->getSubtarget<GCNSubtarget>();
   if (MFI->isEntryFunction() && STM.isAmdHsaOrMesa(MF->getFunction())) {
     SmallString<128> SymbolName;
     getNameWithPrefix(SymbolName, &MF->getFunction()),
     getTargetStreamer()->EmitAMDGPUSymbolType(
         SymbolName, ELF::STT_AMDGPU_HSA_KERNEL);
   }
-  if (STM.dumpCode()) {
+  if (DumpCodeInstEmitter) {
     // Disassemble function name label to text.
     DisasmLines.push_back(MF->getName().str() + ":");
     DisasmLineMaxLen = std::max(DisasmLineMaxLen, DisasmLines.back().size());
     HexLines.push_back("");
   }
 
   AsmPrinter::EmitFunctionEntryLabel();
 }
 
 void AMDGPUAsmPrinter::EmitBasicBlockStart(const MachineBasicBlock &MBB) const {
-  const GCNSubtarget &STI = MBB.getParent()->getSubtarget<GCNSubtarget>();
-  if (STI.dumpCode() && !isBlockOnlyReachableByFallthrough(&MBB)) {
+  if (DumpCodeInstEmitter && !isBlockOnlyReachableByFallthrough(&MBB)) {
     // Write a line for the basic block label if it is not only fallthrough.
     DisasmLines.push_back(
         (Twine("BB") + Twine(getFunctionNumber())
          + "_" + Twine(MBB.getNumber()) + ":").str());
     DisasmLineMaxLen = std::max(DisasmLineMaxLen, DisasmLines.back().size());
     HexLines.push_back("");
   }
   AsmPrinter::EmitBasicBlockStart(MBB);
OutStreamer->emitRawComment(
       " COMPUTE_PGM_RSRC2:TGID_Z_EN: " +
       Twine(G_00B84C_TGID_Z_EN(CurrentProgramInfo.ComputePGMRSrc2)), false);
     OutStreamer->emitRawComment(
       " COMPUTE_PGM_RSRC2:TIDIG_COMP_CNT: " +
       Twine(G_00B84C_TIDIG_COMP_CNT(CurrentProgramInfo.ComputePGMRSrc2)),
       false);
   }
 
-  if (STM.dumpCode()) {
+  if (DumpCodeInstEmitter) {
 
     OutStreamer->SwitchSection(
         Context.getELFSection(".AMDGPU.disasm", ELF::SHT_NOTE, 0));
 
     for (size_t i = 0; i < DisasmLines.size(); ++i) {
       std::string Comment = "\n";
       if (!HexLines[i].empty()) {
         Comment = std::string(DisasmLineMaxLen - DisasmLines[i].size(), ' ');

lib/Target/AMDGPU/AMDGPUMCInstLower.cpp

if (!MI->isPseudo() && STI.isCPUStringValid(STI.getCPU())) {
       std::unique_ptr<MCCodeEmitter> InstEmitter(createSIMCCodeEmitter(
           *STI.getInstrInfo(), *OutContext.getRegisterInfo(), OutContext));
       InstEmitter->encodeInstruction(TmpInst, CodeStream, Fixups, STI);
 
       assert(CodeBytes.size() == STI.getInstrInfo()->getInstSizeInBytes(*MI));
     }
 #endif
 
-    if (STI.dumpCode()) {
-      // Disassemble instruction/operands to text.
+    if (DumpCodeInstEmitter) {
+      // Disassemble instruction/operands to text
       DisasmLines.resize(DisasmLines.size() + 1);
       std::string &DisasmLine = DisasmLines.back();
       raw_string_ostream DisasmStream(DisasmLine);
 
-      AMDGPUInstPrinter InstPrinter(*TM.getMCAsmInfo(),
-                                    *STI.getInstrInfo(),
+      AMDGPUInstPrinter InstPrinter(*TM.getMCAsmInfo(), *STI.getInstrInfo(),
                                     *STI.getRegisterInfo());
       InstPrinter.printInst(&TmpInst, DisasmStream, StringRef(), STI);
 
       // Disassemble instruction/operands to hex representation.
       SmallVector<MCFixup, 4> Fixups;
       SmallVector<char, 16> CodeBytes;
       raw_svector_ostream CodeStream(CodeBytes);
 
-      auto &ObjStreamer = static_cast<MCObjectStreamer&>(*OutStreamer);
-      MCCodeEmitter &InstEmitter = ObjStreamer.getAssembler().getEmitter();
-      InstEmitter.encodeInstruction(TmpInst, CodeStream, Fixups,
-                                    MF->getSubtarget<MCSubtargetInfo>());
+      DumpCodeInstEmitter->encodeInstruction(
+          TmpInst, CodeStream, Fixups, MF->getSubtarget<MCSubtargetInfo>());
       HexLines.resize(HexLines.size() + 1);
       std::string &HexLine = HexLines.back();
       raw_string_ostream HexStream(HexLine);
 
       for (size_t i = 0; i < CodeBytes.size(); i += 4) {
         unsigned int CodeDWord = *(unsigned int *)&CodeBytes[i];
         HexStream << format("%s%08X", (i > 0 ? " " : ""), CodeDWord);
       }