[AMDGPU] Fixed +DumpCode

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.

Differential Revision: https://reviews.llvm.org/D60682

Change-Id: I6436d86fe2ea220d74a643a85e64753747c9366b
llvm-svn: 360688

llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.cpp

@@ -34,6 +34,7 @@
 #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"
@@ -204,6 +205,18 @@ void AMDGPUAsmPrinter::EmitFunctionBodyStart() {
 
   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() {
@@ -261,7 +274,7 @@ void AMDGPUAsmPrinter::EmitFunctionEntryLabel() {
     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());
@@ -272,8 +285,7 @@ void AMDGPUAsmPrinter::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())
@@ -479,7 +491,7 @@ bool AMDGPUAsmPrinter::runOnMachineFunction(MachineFunction &MF) {
       false);
   }
 
-  if (STM.dumpCode()) {
+  if (DumpCodeInstEmitter) {
 
     OutStreamer->SwitchSection(
         Context.getELFSection(".AMDGPU.disasm", ELF::SHT_NOTE, 0));

llvm/lib/Target/AMDGPU/AMDGPUAsmPrinter.h

@@ -32,6 +32,7 @@ namespace llvm {
 
 class AMDGPUMachineFunction;
 class AMDGPUTargetStreamer;
+class MCCodeEmitter;
 class MCOperand;
 class GCNSubtarget;
 
@@ -57,6 +58,8 @@ class AMDGPUAsmPrinter final : public AsmPrinter {
 
   std::unique_ptr<AMDGPU::HSAMD::MetadataStreamer> HSAMetadataStream;
 
+  MCCodeEmitter *DumpCodeInstEmitter = nullptr;
+
   uint64_t getFunctionCodeSize(const MachineFunction &MF) const;
   SIFunctionResourceInfo analyzeResourceUsage(const MachineFunction &MF) const;
 

llvm/lib/Target/AMDGPU/AMDGPUMCInstLower.cpp

@@ -325,14 +325,13 @@ void AMDGPUAsmPrinter::EmitInstruction(const MachineInstr *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);
 
@@ -341,10 +340,8 @@ void AMDGPUAsmPrinter::EmitInstruction(const MachineInstr *MI) {
       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);