[DEBUGINFO, NVPTX] Emit correct debug information for local variables.

[ABataev]

Summary

NVPTX target dos not use register-based frame information. Instead it
relies on the artificial local_depot that is used instead of the frame
and the data for variables must be emitted relatively to this
local_depot.

[echristo]

LGTM.

-eric

include/llvm/CodeGen/AsmPrinter.h

public:
   bool isPositionIndependent() const;
 
   /// Return true if assembly output should contain comments.
   bool isVerbose() const { return VerboseAsm; }
 
   /// Return a unique ID for the current function.
   unsigned getFunctionNumber() const;
 
+  /// Return symbol for the function pseudo stack if the stack frame is not a
+  /// register based.
+  virtual const MCSymbol *getFunctionFrameSymbol() const { return nullptr; }
+
   MCSymbol *getFunctionBegin() const { return CurrentFnBegin; }
   MCSymbol *getFunctionEnd() const { return CurrentFnEnd; }
   MCSymbol *getCurExceptionSym();
 
   /// Return information about object file lowering.
   const TargetLoweringObjectFile &getObjFileLowering() const;
 
   /// Return information about data layout.

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

for (auto &Fragment : DV.getFrameIndexExprs()) {
     int Offset = TFI->getFrameIndexReference(*Asm->MF, Fragment.FI, FrameReg);
     DwarfExpr.addFragmentOffset(Expr);
     SmallVector<uint64_t, 8> Ops;
     Ops.push_back(dwarf::DW_OP_plus_uconst);
     Ops.push_back(Offset);
     Ops.append(Expr->elements_begin(), Expr->elements_end());
     DIExpressionCursor Cursor(Ops);
     DwarfExpr.setMemoryLocationKind();
+    if (const MCSymbol *FrameSymbol = Asm->getFunctionFrameSymbol())
+      addOpAddress(*Loc, FrameSymbol);
+    else
       DwarfExpr.addMachineRegExpression(
           *Asm->MF->getSubtarget().getRegisterInfo(), Cursor, FrameReg);
     DwarfExpr.addExpression(std::move(Cursor));
   }
   addBlock(*VariableDie, dwarf::DW_AT_location, DwarfExpr.finalize());
 
   return VariableDie;
 }
 
 DIE *DwarfCompileUnit::constructVariableDIE(DbgVariable &DV,

lib/Target/NVPTX/NVPTXAsmPrinter.h

public:
   void getAnalysisUsage(AnalysisUsage &AU) const override {
     AU.addRequired<MachineLoopInfo>();
     AsmPrinter::getAnalysisUsage(AU);
   }
 
   bool ignoreLoc(const MachineInstr &);
 
   std::string getVirtualRegisterName(unsigned) const;
+
+  const MCSymbol *getFunctionFrameSymbol() const override;
 };
 
 } // end namespace llvm
 
 #endif // LLVM_LIB_TARGET_NVPTX_NVPTXASMPRINTER_H

lib/Target/NVPTX/NVPTXAsmPrinter.cpp

void NVPTXAsmPrinter::EmitFunctionBodyStart() {
   emitDemotedVars(&MF->getFunction(), O);
   OutStreamer->EmitRawText(O.str());
 }
 
 void NVPTXAsmPrinter::EmitFunctionBodyEnd() {
   VRegMapping.clear();
 }
 
+const MCSymbol *NVPTXAsmPrinter::getFunctionFrameSymbol() const {
+    SmallString<128> Str;
+    raw_svector_ostream(Str) << DEPOTNAME << getFunctionNumber();
+    return OutContext.getOrCreateSymbol(Str);
+}
+
 void NVPTXAsmPrinter::emitImplicitDef(const MachineInstr *MI) const {
   unsigned RegNo = MI->getOperand(0).getReg();
   if (TargetRegisterInfo::isVirtualRegister(RegNo)) {
     OutStreamer->AddComment(Twine("implicit-def: ") +
                             getVirtualRegisterName(RegNo));
   } else {
     OutStreamer->AddComment(Twine("implicit-def: ") +
                             nvptxSubtarget->getRegisterInfo()->getName(RegNo));

lib/Target/NVPTX/NVPTXFrameLowering.h

 class NVPTXSubtarget;
 class NVPTXFrameLowering : public TargetFrameLowering {
 public:
   explicit NVPTXFrameLowering();
 
   bool hasFP(const MachineFunction &MF) const override;
   void emitPrologue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
   void emitEpilogue(MachineFunction &MF, MachineBasicBlock &MBB) const override;
+  int getFrameIndexReference(const MachineFunction &MF, int FI,
+                             unsigned &FrameReg) const override;
 
   MachineBasicBlock::iterator
   eliminateCallFramePseudoInstr(MachineFunction &MF, MachineBasicBlock &MBB,
                                 MachineBasicBlock::iterator I) const override;
 };
 
 } // End llvm namespace
 
 #endif

lib/Target/NVPTX/NVPTXFrameLowering.cpp

if (!MR.use_empty(NVPTX::VRFrame)) {
                .addReg(NVPTX::VRFrameLocal);
     }
     BuildMI(MBB, MI, dl, MF.getSubtarget().getInstrInfo()->get(MovDepotOpcode),
             NVPTX::VRFrameLocal)
         .addImm(MF.getFunctionNumber());
   }
 }
 
+int NVPTXFrameLowering::getFrameIndexReference(const MachineFunction &MF,
+                                               int FI,
+                                               unsigned &FrameReg) const {
+  const MachineFrameInfo &MFI = MF.getFrameInfo();
+  FrameReg = NVPTX::VRDepot;
+  return MFI.getObjectOffset(FI) - getOffsetOfLocalArea();
+}
+
 void NVPTXFrameLowering::emitEpilogue(MachineFunction &MF,
                                       MachineBasicBlock &MBB) const {}
 
 // This function eliminates ADJCALLSTACKDOWN,
 // ADJCALLSTACKUP pseudo instructions
 MachineBasicBlock::iterator NVPTXFrameLowering::eliminateCallFramePseudoInstr(
     MachineFunction &MF, MachineBasicBlock &MBB,
     MachineBasicBlock::iterator I) const {
   // Simply discard ADJCALLSTACKDOWN,
   // ADJCALLSTACKUP instructions.
   return MBB.erase(I);
 }

test/DebugInfo/NVPTX/dbg-declare-alloca.ll

 ; CHECK: // .b8 11                               // DW_AT_byte_size
 ; CHECK: // .b8 11                               // DW_FORM_data1
 ; CHECK: // .b8 0                                // EOM(1)
 ; CHECK: // .b8 0                                // EOM(2)
 ; CHECK: // .b8 0                                // EOM(3)
 ; CHECK: // }
 ; CHECK: // .section .debug_info
 ; CHECK: // {
-; CHECK: // .b32 124                             // Length of Unit
+; CHECK: // .b32 133                             // Length of Unit
 ; CHECK: // .b8 2                                // DWARF version number
 ; CHECK: // .b8 0
 ; CHECK: // .b32 .debug_abbrev                   // Offset Into Abbrev. Section
 ; CHECK: // .b8 8                                // Address Size (in bytes)
-; CHECK: // .b8 1                                // Abbrev [1] 0xb:0x75 DW_TAG_compile_unit
+; CHECK: // .b8 1                                // Abbrev [1] 0xb:0x7e DW_TAG_compile_unit
 ; CHECK: // .b8 99                               // DW_AT_producer
 ; CHECK: // .b8 108
 ; CHECK: // .b8 97
 ; CHECK: // .b8 110
 ; CHECK: // .b8 103
 ; CHECK: // .b8 0
 ; CHECK: // .b8 12                               // DW_AT_language
 ; CHECK: // .b8 0
 ; CHECK: // .b8 116                              // DW_AT_name
 ; CHECK: // .b8 46
 ; CHECK: // .b8 99
 ; CHECK: // .b8 0
 ; CHECK: // .b32 .debug_line                     // DW_AT_stmt_list
 ; CHECK: // .b8 116                              // DW_AT_comp_dir
 ; CHECK: // .b8 101
 ; CHECK: // .b8 115
 ; CHECK: // .b8 116
 ; CHECK: // .b8 0
 ; CHECK: // .b64 Lfunc_begin0                    // DW_AT_low_pc
 ; CHECK: // .b64 Lfunc_end0                      // DW_AT_high_pc
-; CHECK: // .b8 2                                // Abbrev [2] 0x31:0x32 DW_TAG_subprogram
+; CHECK: // .b8 2                                // Abbrev [2] 0x31:0x3b DW_TAG_subprogram
 ; CHECK: // .b64 Lfunc_begin0                    // DW_AT_low_pc
 ; CHECK: // .b64 Lfunc_end0                      // DW_AT_high_pc
 ; CHECK: // .b8 117                              // DW_AT_name
 ; CHECK: // .b8 115
 ; CHECK: // .b8 101
 ; CHECK: // .b8 95
 ; CHECK: // .b8 100
 ; CHECK: // .b8 98
 ; CHECK: // .b8 103
 ; CHECK: // .b8 95
 ; CHECK: // .b8 100
 ; CHECK: // .b8 101
 ; CHECK: // .b8 99
 ; CHECK: // .b8 108
 ; CHECK: // .b8 97
 ; CHECK: // .b8 114
 ; CHECK: // .b8 101
 ; CHECK: // .b8 0
 ; CHECK: // .b8 1                                // DW_AT_decl_file
 ; CHECK: // .b8 3                                // DW_AT_decl_line
 ; CHECK: // .b8 1                                // DW_AT_prototyped
 ; CHECK: // .b8 1                                // DW_AT_external
-; CHECK: // .b8 3                                // Abbrev [3] 0x56:0xc DW_TAG_variable
-; CHECK: // .b8 2                                // DW_AT_location
+; CHECK: // .b8 3                                // Abbrev [3] 0x56:0x15 DW_TAG_variable
+; CHECK: // .b8 11                               // DW_AT_location
+; CHECK: // .b8 3
+; CHECK: // .b64 __local_depot0
 ; CHECK: // .b8 35
-; CHECK: // .b8 8
+; CHECK: // .b8 0
 ; CHECK: // .b8 111                              // DW_AT_name
 ; CHECK: // .b8 0
 ; CHECK: // .b8 1                                // DW_AT_decl_file
 ; CHECK: // .b8 4                                // DW_AT_decl_line
-; CHECK: // .b32 99                              // DW_AT_type
+; CHECK: // .b32 108                             // DW_AT_type
 ; CHECK: // .b8 0                                // End Of Children Mark
-; CHECK: // .b8 4                                // Abbrev [4] 0x63:0x15 DW_TAG_structure_type
+; CHECK: // .b8 4                                // Abbrev [4] 0x6c:0x15 DW_TAG_structure_type
 ; CHECK: // .b8 70                               // DW_AT_name
 ; CHECK: // .b8 111
 ; CHECK: // .b8 111
 ; CHECK: // .b8 0
 ; CHECK: // .b8 4                                // DW_AT_byte_size
 ; CHECK: // .b8 1                                // DW_AT_decl_file
 ; CHECK: // .b8 1                                // DW_AT_decl_line
-; CHECK: // .b8 5                                // Abbrev [5] 0x6b:0xc DW_TAG_member
+; CHECK: // .b8 5                                // Abbrev [5] 0x74:0xc DW_TAG_member
 ; CHECK: // .b8 120                              // DW_AT_name
 ; CHECK: // .b8 0
-; CHECK: // .b32 120                             // DW_AT_type
+; CHECK: // .b32 129                             // DW_AT_type
 ; CHECK: // .b8 1                                // DW_AT_decl_file
 ; CHECK: // .b8 1                                // DW_AT_decl_line
 ; CHECK: // .b8 2                                // DW_AT_data_member_location
 ; CHECK: // .b8 35
 ; CHECK: // .b8 0
 ; CHECK: // .b8 0                                // End Of Children Mark
-; CHECK: // .b8 6                                // Abbrev [6] 0x78:0x7 DW_TAG_base_type
+; CHECK: // .b8 6                                // Abbrev [6] 0x81:0x7 DW_TAG_base_type
 ; CHECK: // .b8 105                              // DW_AT_name
 ; CHECK: // .b8 110
 ; CHECK: // .b8 116
 ; CHECK: // .b8 0
 ; CHECK: // .b8 5                                // DW_AT_encoding
 ; CHECK: // .b8 4                                // DW_AT_byte_size
 ; CHECK: // .b8 0                                // End Of Children Mark
 ; CHECK: // }