[DEBUG_INFO][NVPTX] Generate DW_AT_address_class to get the values in debugger.

[ABataev]

Summary

According to
https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf,
the compiler should emit the DW_AT_address_class attribute for all
variable and parameter. It means, that DW_AT_address_class attribute
should be used in the non-standard way to support compatibility with the
cuda-gdb debugger.
Clang is able to generate the information about the variable address
class. This information is emitted as the expression sequence
DW_OP_constu <DWARF Address Space> DW_OP_swap DW_OP_xderef. The patch
tries to find all such expressions and transform them into
DW_AT_address_class <DWARF Address Space> if target is NVPTX and the debugger is gdb.
If the expression is not found, then default values are used. For the
local variables <DWARF Address Space> is set to ADDR_local_space(6), for
the globals <DWARF Address Space> is set to ADDR_global_space(5). The
values are taken from the table in the same section 5.2. CUDA-Specific
DWARF Definitions.

[ABataev]

Ping!

[ABataev]

Ping!

[aprantl]

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

112 ↗

(On Diff #183313)

This should be a member function of DIExpression instead. We have other similar properties there already.

113 ↗

(On Diff #183313)

This is not general enough. You probably want to check that the last 4 elements of the DIExpression match this pattern instead, since the LLVM optimizer may insert additional operations at the beginning of the Expression at any time.

[ABataev]

Reworked according to the comments from Adrian Prantl.

[ABataev]

Adrian, thanks a lot for the review!

lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

112 ↗

(On Diff #183313)

Made it a static member function instead of the DIExpression class. Need to modify the expression by deleting the last 4 elements after AddressClass extraction, but function is applied to const expressions. Need to create the new expression, if the pattern was recognized.

[aprantl]

include/llvm/IR/DebugInfoMetadata.h

2516 ↗

(On Diff #185348)

I understand that you copied the interface from the function above, but could you please make it

Optional<unsigned> getAddressClass() const;

instead?

We should also change extractIfOffset this way...

[ABataev]

include/llvm/IR/DebugInfoMetadata.h

2516 ↗

(On Diff #185348)

I cannot make it const, it modifies the expression itself and should build the new expression if the pattern is found.

[ABataev]

include/llvm/IR/DebugInfoMetadata.h

2516 ↗

(On Diff #185348)

I mean, it should(!) modify the expression itself, but I can not do it, because this function is applied to the constant expressions.

[aprantl]

Sorry, I overlooked the second part of the function.

llvm/trunk/include/llvm/IR/DebugInfoMetadata.h

public:
 
   /// Append \p Ops with operations to apply the \p Offset.
   static void appendOffset(SmallVectorImpl<uint64_t> &Ops, int64_t Offset);
 
   /// If this is a constant offset, extract it. If there is no expression,
   /// return true with an offset of zero.
   bool extractIfOffset(int64_t &Offset) const;
 
+  /// Checks if the last 4 elements of the expression are DW_OP_constu <DWARF
+  /// Address Space> DW_OP_swap DW_OP_xderef and extracts the <DWARF Address
+  /// Space>.
+  static const DIExpression *extractAddressClass(const DIExpression *Expr,
+                                                 unsigned &AddrClass);
+
   /// Constants for DIExpression::prepend.
   enum { NoDeref = false, WithDeref = true, WithStackValue = true };
 
   /// Prepend \p DIExpr with a deref and offset operation and optionally turn it
   /// into a stack value.
   static DIExpression *prepend(const DIExpression *Expr, bool DerefBefore,
                                int64_t Offset = 0, bool DerefAfter = false,
                                bool StackValue = false);

llvm/trunk/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

addUInt(*VariableDIE, dwarf::DW_AT_alignment, dwarf::DW_FORM_udata,
             AlignInBytes);
 
   if (MDTuple *TP = GV->getTemplateParams())
     addTemplateParams(*VariableDIE, DINodeArray(TP));
 
   // Add location.
   bool addToAccelTable = false;
   DIELoc *Loc = nullptr;
+  Optional<unsigned> NVPTXAddressSpace;
   std::unique_ptr<DIEDwarfExpression> DwarfExpr;
   for (const auto &GE : GlobalExprs) {
     const GlobalVariable *Global = GE.Var;
     const DIExpression *Expr = GE.Expr;
 
     // For compatibility with DWARF 3 and earlier,
     // DW_AT_location(DW_OP_constu, X, DW_OP_stack_value) becomes
     // DW_AT_const_value(X).
if (Global && Global->isThreadLocal() &&
       continue;
 
     if (!Loc) {
       addToAccelTable = true;
       Loc = new (DIEValueAllocator) DIELoc;
       DwarfExpr = llvm::make_unique<DIEDwarfExpression>(*Asm, *this, *Loc);
     }
 
-    if (Expr)
+    if (Expr) {
+      // According to
+      // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+      // cuda-gdb requires DW_AT_address_class for all variables to be able to
+      // correctly interpret address space of the variable address.
+      // Decode DW_OP_constu <DWARF Address Space> DW_OP_swap DW_OP_xderef
+      // sequence for the NVPTX + gdb target.
+      unsigned LocalNVPTXAddressSpace;
+      if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+        const DIExpression *NewExpr =
+            DIExpression::extractAddressClass(Expr, LocalNVPTXAddressSpace);
+        if (NewExpr != Expr) {
+          Expr = NewExpr;
+          NVPTXAddressSpace = LocalNVPTXAddressSpace;
+        }
+      }
       DwarfExpr->addFragmentOffset(Expr);
+    }
 
     if (Global) {
       const MCSymbol *Sym = Asm->getSymbol(Global);
       if (Global->isThreadLocal()) {
         if (Asm->TM.useEmulatedTLS()) {
           // TODO: add debug info for emulated thread local mode.
         } else {
           // FIXME: Make this work with -gsplit-dwarf.
for (const auto &GE : GlobalExprs) {
     // Global variables attached to symbols are memory locations.
     // It would be better if this were unconditional, but malformed input that
     // mixes non-fragments and fragments for the same variable is too expensive
     // to detect in the verifier.
     if (DwarfExpr->isUnknownLocation())
       DwarfExpr->setMemoryLocationKind();
     DwarfExpr->addExpression(Expr);
   }
+  if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+    // According to
+    // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+    // cuda-gdb requires DW_AT_address_class for all variables to be able to
+    // correctly interpret address space of the variable address.
+    const unsigned NVPTX_ADDR_global_space = 5;
+    addUInt(*VariableDIE, dwarf::DW_AT_address_class, dwarf::DW_FORM_data1,
+            NVPTXAddressSpace ? *NVPTXAddressSpace : NVPTX_ADDR_global_space);
+  }
   if (Loc)
     addBlock(*VariableDIE, dwarf::DW_AT_location, DwarfExpr->finalize());
 
   if (DD->useAllLinkageNames())
     addLinkageName(*VariableDIE, GV->getLinkageName());
 
   if (addToAccelTable) {
     DD->addAccelName(*CUNode, GV->getName(), *VariableDIE);
if (const MachineInstr *DVInsn = DV.getMInsn()) {
 
     return VariableDie;
   }
 
   // .. else use frame index.
   if (!DV.hasFrameIndexExprs())
     return VariableDie;
 
+  Optional<unsigned> NVPTXAddressSpace;
   DIELoc *Loc = new (DIEValueAllocator) DIELoc;
   DIEDwarfExpression DwarfExpr(*Asm, *this, *Loc);
   for (auto &Fragment : DV.getFrameIndexExprs()) {
     unsigned FrameReg = 0;
     const DIExpression *Expr = Fragment.Expr;
     const TargetFrameLowering *TFI = Asm->MF->getSubtarget().getFrameLowering();
     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);
+    // According to
+    // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+    // cuda-gdb requires DW_AT_address_class for all variables to be able to
+    // correctly interpret address space of the variable address.
+    // Decode DW_OP_constu <DWARF Address Space> DW_OP_swap DW_OP_xderef
+    // sequence for the NVPTX + gdb target.
+    unsigned LocalNVPTXAddressSpace;
+    if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+      const DIExpression *NewExpr =
+          DIExpression::extractAddressClass(Expr, LocalNVPTXAddressSpace);
+      if (NewExpr != Expr) {
+        Expr = NewExpr;
+        NVPTXAddressSpace = LocalNVPTXAddressSpace;
+      }
+    }
+    if (Expr)
       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));
   }
+  if (Asm->TM.getTargetTriple().isNVPTX() && DD->tuneForGDB()) {
+    // According to
+    // https://docs.nvidia.com/cuda/archive/10.0/ptx-writers-guide-to-interoperability/index.html#cuda-specific-dwarf
+    // cuda-gdb requires DW_AT_address_class for all variables to be able to
+    // correctly interpret address space of the variable address.
+    const unsigned NVPTX_ADDR_local_space = 6;
+    addUInt(*VariableDie, dwarf::DW_AT_address_class, dwarf::DW_FORM_data1,
+            NVPTXAddressSpace ? *NVPTXAddressSpace : NVPTX_ADDR_local_space);
+  }
   addBlock(*VariableDie, dwarf::DW_AT_location, DwarfExpr.finalize());
 
   return VariableDie;
 }
 
 DIE *DwarfCompileUnit::constructVariableDIE(DbgVariable &DV,
                                             const LexicalScope &Scope,
                                             DIE *&ObjectPointer) {

llvm/trunk/lib/IR/DebugInfoMetadata.cpp

if (Elements[2] == dwarf::DW_OP_minus) {
       Offset = -Elements[1];
       return true;
     }
   }
 
   return false;
 }
 
+const DIExpression *DIExpression::extractAddressClass(const DIExpression *Expr,
+                                                      unsigned &AddrClass) {
+  const unsigned PatternSize = 4;
+  if (Expr->Elements.size() >= PatternSize &&
+      Expr->Elements[PatternSize - 4] == dwarf::DW_OP_constu &&
+      Expr->Elements[PatternSize - 2] == dwarf::DW_OP_swap &&
+      Expr->Elements[PatternSize - 1] == dwarf::DW_OP_xderef) {
+    AddrClass = Expr->Elements[PatternSize - 3];
+
+    if (Expr->Elements.size() == PatternSize)
+      return nullptr;
+    return DIExpression::get(Expr->getContext(),
+                             makeArrayRef(&*Expr->Elements.begin(),
+                                          Expr->Elements.size() - PatternSize));
+  }
+  return Expr;
+}
+
 DIExpression *DIExpression::prepend(const DIExpression *Expr, bool DerefBefore,
                                     int64_t Offset, bool DerefAfter,
                                     bool StackValue) {
   SmallVector<uint64_t, 8> Ops;
   if (DerefBefore)
     Ops.push_back(dwarf::DW_OP_deref);
 
   appendOffset(Ops, Offset);

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

 ; CHECK-NEXT: .b8 12                               // DW_FORM_flag
 ; CHECK-NEXT: .b8 63                               // DW_AT_external
 ; CHECK-NEXT: .b8 12                               // DW_FORM_flag
 ; CHECK-NEXT: .b8 0                                // EOM(1)
 ; CHECK-NEXT: .b8 0                                // EOM(2)
 ; CHECK-NEXT: .b8 3                                // Abbreviation Code
 ; CHECK-NEXT: .b8 52                               // DW_TAG_variable
 ; CHECK-NEXT: .b8 0                                // DW_CHILDREN_no
+; CHECK-NEXT: .b8 51                               // DW_AT_address_class
+; CHECK-NEXT: .b8 11                               // DW_FORM_data1
 ; CHECK-NEXT: .b8 2                                // DW_AT_location
 ; CHECK-NEXT: .b8 10                               // DW_FORM_block1
 ; CHECK-NEXT: .b8 3                                // DW_AT_name
 ; CHECK-NEXT: .b8 8                                // DW_FORM_string
 ; CHECK-NEXT: .b8 58                               // DW_AT_decl_file
 ; CHECK-NEXT: .b8 11                               // DW_FORM_data1
 ; CHECK-NEXT: .b8 59                               // DW_AT_decl_line
 ; CHECK-NEXT: .b8 11                               // DW_FORM_data1

 ; CHECK-NEXT: .b8 11                               // DW_AT_byte_size
 ; CHECK-NEXT: .b8 11                               // DW_FORM_data1
 ; CHECK-NEXT: .b8 0                                // EOM(1)
 ; CHECK-NEXT: .b8 0                                // EOM(2)
 ; CHECK-NEXT: .b8 0                                // EOM(3)
 ; CHECK-NEXT: }
 ; CHECK-NEXT: .section .debug_info
 ; CHECK-NEXT: {
-; CHECK-NEXT: .b32 135                             // Length of Unit
+; CHECK-NEXT: .b32 136                             // Length of Unit
 ; CHECK-NEXT: .b8 2                                // DWARF version number
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b32 .debug_abbrev                   // Offset Into Abbrev. Section
 ; CHECK-NEXT: .b8 8                                // Address Size (in bytes)
-; CHECK-NEXT: .b8 1                                // Abbrev [1] 0xb:0x80 DW_TAG_compile_unit
+; CHECK-NEXT: .b8 1                                // Abbrev [1] 0xb:0x81 DW_TAG_compile_unit
 ; CHECK-NEXT: .b8 99,108,97,110,103                // DW_AT_producer
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 12                               // DW_AT_language
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 116,46,99                        // DW_AT_name
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b32 .debug_line                     // DW_AT_stmt_list
 ; CHECK-NEXT: .b8 116,101,115,116                  // DW_AT_comp_dir
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b64 Lfunc_begin0                    // DW_AT_low_pc
 ; CHECK-NEXT: .b64 Lfunc_end0                      // DW_AT_high_pc
-; CHECK-NEXT: .b8 2                                // Abbrev [2] 0x31:0x3d DW_TAG_subprogram
+; CHECK-NEXT: .b8 2                                // Abbrev [2] 0x31:0x3e DW_TAG_subprogram
 ; CHECK-NEXT: .b64 Lfunc_begin0                    // DW_AT_low_pc
 ; CHECK-NEXT: .b64 Lfunc_end0                      // DW_AT_high_pc
 ; CHECK-NEXT: .b8 1                                // DW_AT_frame_base
 ; CHECK-NEXT: .b8 156
 ; CHECK-NEXT: .b8 117,115,101,95,100,98,103,95,100,101,99,108,97,114,101 // DW_AT_name
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 1                                // DW_AT_decl_file
 ; CHECK-NEXT: .b8 3                                // DW_AT_decl_line
 ; CHECK-NEXT: .b8 1                                // DW_AT_prototyped
 ; CHECK-NEXT: .b8 1                                // DW_AT_external
-; CHECK-NEXT: .b8 3                                // Abbrev [3] 0x58:0x15 DW_TAG_variable
+; CHECK-NEXT: .b8 3                                // Abbrev [3] 0x58:0x16 DW_TAG_variable
+; CHECK-NEXT: .b8 6                                // DW_AT_address_class
 ; CHECK-NEXT: .b8 11                               // DW_AT_location
 ; CHECK-NEXT: .b8 3
 ; CHECK-NEXT: .b64 __local_depot0
 ; CHECK-NEXT: .b8 35
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 111                              // DW_AT_name
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 1                                // DW_AT_decl_file
 ; CHECK-NEXT: .b8 4                                // DW_AT_decl_line
-; CHECK-NEXT: .b32 110                             // DW_AT_type
+; CHECK-NEXT: .b32 111                             // DW_AT_type
 ; CHECK-NEXT: .b8 0                                // End Of Children Mark
-; CHECK-NEXT: .b8 4                                // Abbrev [4] 0x6e:0x15 DW_TAG_structure_type
+; CHECK-NEXT: .b8 4                                // Abbrev [4] 0x6f:0x15 DW_TAG_structure_type
 ; CHECK-NEXT: .b8 70,111,111                       // DW_AT_name
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 4                                // DW_AT_byte_size
 ; CHECK-NEXT: .b8 1                                // DW_AT_decl_file
 ; CHECK-NEXT: .b8 1                                // DW_AT_decl_line
-; CHECK-NEXT: .b8 5                                // Abbrev [5] 0x76:0xc DW_TAG_member
+; CHECK-NEXT: .b8 5                                // Abbrev [5] 0x77:0xc DW_TAG_member
 ; CHECK-NEXT: .b8 120                              // DW_AT_name
 ; CHECK-NEXT: .b8 0
-; CHECK-NEXT: .b32 131                             // DW_AT_type
+; CHECK-NEXT: .b32 132                             // DW_AT_type
 ; CHECK-NEXT: .b8 1                                // DW_AT_decl_file
 ; CHECK-NEXT: .b8 1                                // DW_AT_decl_line
 ; CHECK-NEXT: .b8 2                                // DW_AT_data_member_location
 ; CHECK-NEXT: .b8 35
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 0                                // End Of Children Mark
-; CHECK-NEXT: .b8 6                                // Abbrev [6] 0x83:0x7 DW_TAG_base_type
+; CHECK-NEXT: .b8 6                                // Abbrev [6] 0x84:0x7 DW_TAG_base_type
 ; CHECK-NEXT: .b8 105,110,116                      // DW_AT_name
 ; CHECK-NEXT: .b8 0
 ; CHECK-NEXT: .b8 5                                // DW_AT_encoding
 ; CHECK-NEXT: .b8 4                                // DW_AT_byte_size
 ; CHECK-NEXT: .b8 0                                // End Of Children Mark
 ; CHECK-NEXT: }
 
 %struct.Foo = type { i32 }

llvm/trunk/test/DebugInfo/NVPTX/debug-addr-class.ll

+; RUN: llc -mtriple=nvptx64-nvidia-cuda < %s | FileCheck %s
+
+@GLOBAL = addrspace(1) externally_initialized global i32 0, align 4, !dbg !0
+@SHARED = addrspace(3) externally_initialized global i32 undef, align 4, !dbg !6
+
+define void @test(float, float*, float*, i32) !dbg !17 {
+  %5 = alloca float, align 4
+  %6 = alloca float*, align 8
+  %7 = alloca float*, align 8
+  %8 = alloca i32, align 4
+  store float %0, float* %5, align 4
+  call void @llvm.dbg.declare(metadata float* %5, metadata !22, metadata !DIExpression()), !dbg !23
+  store float* %1, float** %6, align 8
+  call void @llvm.dbg.declare(metadata float** %6, metadata !24, metadata !DIExpression()), !dbg !25
+  store float* %2, float** %7, align 8
+  call void @llvm.dbg.declare(metadata float** %7, metadata !26, metadata !DIExpression()), !dbg !27
+  store i32 %3, i32* %8, align 4
+  call void @llvm.dbg.declare(metadata i32* %8, metadata !28, metadata !DIExpression()), !dbg !29
+  %9 = load float, float* %5, align 4, !dbg !30
+  %10 = load float*, float** %6, align 8, !dbg !31
+  %11 = load i32, i32* %8, align 4, !dbg !32
+  %12 = sext i32 %11 to i64, !dbg !31
+  %13 = getelementptr inbounds float, float* %10, i64 %12, !dbg !31
+  %14 = load float, float* %13, align 4, !dbg !31
+  %15 = fmul contract float %9, %14, !dbg !33
+  %16 = load float*, float** %7, align 8, !dbg !34
+  %17 = load i32, i32* %8, align 4, !dbg !35
+  %18 = sext i32 %17 to i64, !dbg !34
+  %19 = getelementptr inbounds float, float* %16, i64 %18, !dbg !34
+  store float %15, float* %19, align 4, !dbg !36
+  store i32 0, i32* addrspacecast (i32 addrspace(1)* @GLOBAL to i32*), align 4, !dbg !37
+  store i32 0, i32* addrspacecast (i32 addrspace(3)* @SHARED to i32*), align 4, !dbg !38
+  ret void, !dbg !39
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata)
+
+!llvm.dbg.cu = !{!2}
+!nvvm.annotations = !{!10}
+!llvm.module.flags = !{!11, !12, !13, !14, !15}
+!llvm.ident = !{!16}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "GLOBAL", scope: !2, file: !8, line: 3, type: !9, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang version 9.0.0 (trunk 351969) (llvm/trunk 351973)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
+!3 = !DIFile(filename: "new.cc", directory: "/tmp")
+!4 = !{}
+!5 = !{!0, !6}
+!6 = !DIGlobalVariableExpression(var: !7, expr: !DIExpression(DW_OP_constu, 8, DW_OP_swap, DW_OP_xderef))
+!7 = distinct !DIGlobalVariable(name: "SHARED", scope: !2, file: !8, line: 4, type: !9, isLocal: false, isDefinition: true)
+!8 = !DIFile(filename: "test.cu", directory: "/tmp")
+!9 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!10 = !{void (float, float*, float*, i32)* @test, !"kernel", i32 1}
+!11 = !{i32 2, !"Dwarf Version", i32 2}
+!12 = !{i32 2, !"Debug Info Version", i32 3}
+!13 = !{i32 1, !"wchar_size", i32 4}
+!14 = !{i32 4, !"nvvm-reflect-ftz", i32 0}
+!15 = !{i32 7, !"PIC Level", i32 2}
+!16 = !{!"clang version 9.0.0 (trunk 351969) (llvm/trunk 351973)"}
+!17 = distinct !DISubprogram(name: "test", linkageName: "test", scope: !8, file: !8, line: 6, type: !18, scopeLine: 6, flags: DIFlagPrototyped, spFlags: DISPFlagDefinition, unit: !2, retainedNodes: !4)
+!18 = !DISubroutineType(types: !19)
+!19 = !{null, !20, !21, !21, !9}
+!20 = !DIBasicType(name: "float", size: 32, encoding: DW_ATE_float)
+!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !20, size: 64)
+!22 = !DILocalVariable(name: "a", arg: 1, scope: !17, file: !8, line: 6, type: !20)
+!23 = !DILocation(line: 6, column: 41, scope: !17)
+!24 = !DILocalVariable(name: "x", arg: 2, scope: !17, file: !8, line: 6, type: !21)
+!25 = !DILocation(line: 6, column: 51, scope: !17)
+!26 = !DILocalVariable(name: "y", arg: 3, scope: !17, file: !8, line: 6, type: !21)
+!27 = !DILocation(line: 6, column: 61, scope: !17)
+!28 = !DILocalVariable(name: "i", arg: 4, scope: !17, file: !8, line: 6, type: !9)
+!29 = !DILocation(line: 6, column: 68, scope: !17)
+!30 = !DILocation(line: 7, column: 10, scope: !17)
+!31 = !DILocation(line: 7, column: 14, scope: !17)
+!32 = !DILocation(line: 7, column: 16, scope: !17)
+!33 = !DILocation(line: 7, column: 12, scope: !17)
+!34 = !DILocation(line: 7, column: 3, scope: !17)
+!35 = !DILocation(line: 7, column: 5, scope: !17)
+!36 = !DILocation(line: 7, column: 8, scope: !17)
+!37 = !DILocation(line: 8, column: 10, scope: !17)
+!38 = !DILocation(line: 9, column: 10, scope: !17)
+!39 = !DILocation(line: 10, column: 1, scope: !17)
+
+; CHECK: .section .debug_abbrev
+; CHECK-NEXT: {
+; CHECK-NEXT: .b8 1                                   // Abbreviation Code
+; CHECK-NEXT: .b8 17                                  // DW_TAG_compile_unit
+; CHECK-NEXT: .b8 1                                   // DW_CHILDREN_yes
+; CHECK-NEXT: .b8 37                                  // DW_AT_producer
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 19                                  // DW_AT_language
+; CHECK-NEXT: .b8 5                                   // DW_FORM_data2
+; CHECK-NEXT: .b8 3                                   // DW_AT_name
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 16                                  // DW_AT_stmt_list
+; CHECK-NEXT: .b8 6                                   // DW_FORM_data4
+; CHECK-NEXT: .b8 27                                  // DW_AT_comp_dir
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 17                                  // DW_AT_low_pc
+; CHECK-NEXT: .b8 1                                   // DW_FORM_addr
+; CHECK-NEXT: .b8 18                                  // DW_AT_high_pc
+; CHECK-NEXT: .b8 1                                   // DW_FORM_addr
+; CHECK-NEXT: .b8 0                                   // EOM(1)
+; CHECK-NEXT: .b8 0                                   // EOM(2)
+; CHECK-NEXT: .b8 2                                   // Abbreviation Code
+; CHECK-NEXT: .b8 52                                  // DW_TAG_variable
+; CHECK-NEXT: .b8 0                                   // DW_CHILDREN_no
+; CHECK-NEXT: .b8 3                                   // DW_AT_name
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 73                                  // DW_AT_type
+; CHECK-NEXT: .b8 19                                  // DW_FORM_ref4
+; CHECK-NEXT: .b8 63                                  // DW_AT_external
+; CHECK-NEXT: .b8 12                                  // DW_FORM_flag
+; CHECK-NEXT: .b8 58                                  // DW_AT_decl_file
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 59                                  // DW_AT_decl_line
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 51                                  // DW_AT_address_class
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 2                                   // DW_AT_location
+; CHECK-NEXT: .b8 10                                  // DW_FORM_block1
+; CHECK-NEXT: .b8 0                                   // EOM(1)
+; CHECK-NEXT: .b8 0                                   // EOM(2)
+; CHECK-NEXT: .b8 3                                   // Abbreviation Code
+; CHECK-NEXT: .b8 36                                  // DW_TAG_base_type
+; CHECK-NEXT: .b8 0                                   // DW_CHILDREN_no
+; CHECK-NEXT: .b8 3                                   // DW_AT_name
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 62                                  // DW_AT_encoding
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 11                                  // DW_AT_byte_size
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 0                                   // EOM(1)
+; CHECK-NEXT: .b8 0                                   // EOM(2)
+; CHECK-NEXT: .b8 4                                   // Abbreviation Code
+; CHECK-NEXT: .b8 46                                  // DW_TAG_subprogram
+; CHECK-NEXT: .b8 1                                   // DW_CHILDREN_yes
+; CHECK-NEXT: .b8 17                                  // DW_AT_low_pc
+; CHECK-NEXT: .b8 1                                   // DW_FORM_addr
+; CHECK-NEXT: .b8 18                                  // DW_AT_high_pc
+; CHECK-NEXT: .b8 1                                   // DW_FORM_addr
+; CHECK-NEXT: .b8 64                                  // DW_AT_frame_base
+; CHECK-NEXT: .b8 10                                  // DW_FORM_block1
+; CHECK-NEXT: .b8 135,64                              // DW_AT_MIPS_linkage_name
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 3                                   // DW_AT_name
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 58                                  // DW_AT_decl_file
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 59                                  // DW_AT_decl_line
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 63                                  // DW_AT_external
+; CHECK-NEXT: .b8 12                                  // DW_FORM_flag
+; CHECK-NEXT: .b8 0                                   // EOM(1)
+; CHECK-NEXT: .b8 0                                   // EOM(2)
+; CHECK-NEXT: .b8 5                                   // Abbreviation Code
+; CHECK-NEXT: .b8 5                                   // DW_TAG_formal_parameter
+; CHECK-NEXT: .b8 0                                   // DW_CHILDREN_no
+; CHECK-NEXT: .b8 3                                   // DW_AT_name
+; CHECK-NEXT: .b8 8                                   // DW_FORM_string
+; CHECK-NEXT: .b8 58                                  // DW_AT_decl_file
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 59                                  // DW_AT_decl_line
+; CHECK-NEXT: .b8 11                                  // DW_FORM_data1
+; CHECK-NEXT: .b8 73                                  // DW_AT_type
+; CHECK-NEXT: .b8 19                                  // DW_FORM_ref4
+; CHECK-NEXT: .b8 0                                   // EOM(1)
+; CHECK-NEXT: .b8 0                                   // EOM(2)
+; CHECK-NEXT: .b8 0                                   // EOM(3)
+; CHECK-NEXT: }
+; CHECK-NEXT: .section .debug_info
+; CHECK-NEXT: {
+; CHECK-NEXT: .b32 217                                // Length of Unit
+; CHECK-NEXT: .b8 2                                   // DWARF version number
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b32 .debug_abbrev                      // Offset Into Abbrev. Section
+; CHECK-NEXT: .b8 8                                   // Address Size (in bytes)
+; CHECK-NEXT: .b8 1                                   // Abbrev [1] 0xb:0xd2 DW_TAG_compile_unit
+; CHECK-NEXT: .b8 99,108,97,110,103,32,118,101,114,115,105,111,110,32,57,46,48,46,48,32,40,116,114,117,110,107,32,51,53,49,57,54,57,41,32,40,108,108,118,109 // DW_AT_producer
+; CHECK-NEXT: .b8 47,116,114,117,110,107,32,51,53,49,57,55,51,41
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 4                                   // DW_AT_language
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 110,101,119,46,99,99                // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b32 .debug_line                        // DW_AT_stmt_list
+; CHECK-NEXT: .b8 47,116,109,112                      // DW_AT_comp_dir
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b64 Lfunc_begin0                       // DW_AT_low_pc
+; CHECK-NEXT: .b64 Lfunc_end0                         // DW_AT_high_pc
+; CHECK-NEXT: .b8 2                                   // Abbrev [2] 0x65:0x1a DW_TAG_variable
+; CHECK-NEXT: .b8 71,76,79,66,65,76                   // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b32 127                                // DW_AT_type
+; CHECK-NEXT: .b8 1                                   // DW_AT_external
+; CHECK-NEXT: .b8 1                                   // DW_AT_decl_file
+; CHECK-NEXT: .b8 3                                   // DW_AT_decl_line
+; CHECK-NEXT: .b8 5                                   // DW_AT_address_class
+; CHECK-NEXT: .b8 9                                   // DW_AT_location
+; CHECK-NEXT: .b8 3
+; CHECK-NEXT: .b64 GLOBAL
+; CHECK-NEXT: .b8 3                                   // Abbrev [3] 0x7f:0x7 DW_TAG_base_type
+; CHECK-NEXT: .b8 105,110,116                         // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 5                                   // DW_AT_encoding
+; CHECK-NEXT: .b8 4                                   // DW_AT_byte_size
+; CHECK-NEXT: .b8 2                                   // Abbrev [2] 0x86:0x1a DW_TAG_variable
+; CHECK-NEXT: .b8 83,72,65,82,69,68                   // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b32 127                                // DW_AT_type
+; CHECK-NEXT: .b8 1                                   // DW_AT_external
+; CHECK-NEXT: .b8 1                                   // DW_AT_decl_file
+; CHECK-NEXT: .b8 4                                   // DW_AT_decl_line
+; CHECK-NEXT: .b8 8                                   // DW_AT_address_class
+; CHECK-NEXT: .b8 9                                   // DW_AT_location
+; CHECK-NEXT: .b8 3
+; CHECK-NEXT: .b64 SHARED
+; CHECK-NEXT: .b8 4                                   // Abbrev [4] 0xa0:0x33 DW_TAG_subprogram
+; CHECK-NEXT: .b64 Lfunc_begin0                       // DW_AT_low_pc
+; CHECK-NEXT: .b64 Lfunc_end0                         // DW_AT_high_pc
+; CHECK-NEXT: .b8 1                                   // DW_AT_frame_base
+; CHECK-NEXT: .b8 156
+; CHECK-NEXT: .b8 116,101,115,116                     // DW_AT_MIPS_linkage_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 116,101,115,116                     // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 1                                   // DW_AT_decl_file
+; CHECK-NEXT: .b8 6                                   // DW_AT_decl_line
+; CHECK-NEXT: .b8 1                                   // DW_AT_external
+; CHECK-NEXT: .b8 5                                   // Abbrev [5] 0xc0:0x9 DW_TAG_formal_parameter
+; CHECK-NEXT: .b8 97                                  // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 1                                   // DW_AT_decl_file
+; CHECK-NEXT: .b8 6                                   // DW_AT_decl_line
+; CHECK-NEXT: .b32 211                                // DW_AT_type
+; CHECK-NEXT: .b8 5                                   // Abbrev [5] 0xc9:0x9 DW_TAG_formal_parameter
+; CHECK-NEXT: .b8 105                                 // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 1                                   // DW_AT_decl_file
+; CHECK-NEXT: .b8 6                                   // DW_AT_decl_line
+; CHECK-NEXT: .b32 127                                // DW_AT_type
+; CHECK-NEXT: .b8 0                                   // End Of Children Mark
+; CHECK-NEXT: .b8 3                                   // Abbrev [3] 0xd3:0x9 DW_TAG_base_type
+; CHECK-NEXT: .b8 102,108,111,97,116                  // DW_AT_name
+; CHECK-NEXT: .b8 0
+; CHECK-NEXT: .b8 4                                   // DW_AT_encoding
+; CHECK-NEXT: .b8 4                                   // DW_AT_byte_size
+; CHECK-NEXT: .b8 0                                   // End Of Children Mark
+; CHECK-NEXT: }
+; CHECK-NEXT: .section .debug_macinfo
+; CHECK-NEXT: {
+; CHECK-NEXT: .b8 0                                   // End Of Macro List Mark
+; CHECK:      }
+