[BPF] add proper multi-dimensional array support

[yonghong-song]

Summary

For multi-dimensional array like below
  int a[2][3];
the previous implementation generates BTF_KIND_ARRAY type
like below:
  . element_type: int
  . index_type: unsigned int
  . number of elements: 6

This is not the best way to represent arrays, esp.,
when converting BTF back to headers and users will see
  int a[6];
instead.

This patch generates proper support for multi-dimensional arrays.
For "int a[2][3]", the two BTF_KIND_ARRAY types will be
generated:
  Type #n:
    . element_type: int
    . index_type: unsigned int
    . number of elements: 3
  Type #(n+1):
    . element_type: #n
    . index_type: unsigned int
    . number of elements: 2

The linux kernel already supports such a multi-dimensional
array representation properly.

lib/Target/BPF/BTFDebug.h

uint32_t getSize() {
     return BTFTypeBase::getSize() + EnumValues.size() * BTF::BTFEnumSize;
   }
   void completeType(BTFDebug &BDebug);
   void emitType(MCStreamer &OS);
 };
 
 /// Handle array type.
 class BTFTypeArray : public BTFTypeBase {
-  const DICompositeType *ATy;
   struct BTF::BTFArray ArrayInfo;
 
 public:
-  BTFTypeArray(const DICompositeType *ATy);
+  BTFTypeArray(uint32_t ElemTypeId, uint32_t NumElems);
   uint32_t getSize() { return BTFTypeBase::getSize() + BTF::BTFArraySize; }
   void completeType(BTFDebug &BDebug);
   void emitType(MCStreamer &OS);
 };
 
 /// Handle struct/union type.
 class BTFTypeStruct : public BTFTypeBase {
   const DICompositeType *STy;

lib/Target/BPF/BTFDebug.cpp

 void BTFTypeEnum::emitType(MCStreamer &OS) {
   BTFTypeBase::emitType(OS);
   for (const auto &Enum : EnumValues) {
     OS.EmitIntValue(Enum.NameOff, 4);
     OS.EmitIntValue(Enum.Val, 4);
   }
 }
 
-BTFTypeArray::BTFTypeArray(const DICompositeType *ATy) : ATy(ATy) {
+BTFTypeArray::BTFTypeArray(uint32_t ElemTypeId, uint32_t NumElems) {
   Kind = BTF::BTF_KIND_ARRAY;
+  BTFType.NameOff = 0;
   BTFType.Info = Kind << 24;
+  BTFType.Size = 0;
+
+  ArrayInfo.ElemType = ElemTypeId;
+  ArrayInfo.Nelems = NumElems;
 }
 
-/// Represent a BTF array. BTF does not record array dimensions,
-/// so conceptually a BTF array is a one-dimensional array.
+/// Represent a BTF array.
 void BTFTypeArray::completeType(BTFDebug &BDebug) {
-  BTFType.NameOff = BDebug.addString(ATy->getName());
-  BTFType.Size = 0;
-
-  auto *BaseType = ATy->getBaseType().resolve();
-  ArrayInfo.ElemType = BDebug.getTypeId(BaseType);
 
   // The IR does not really have a type for the index.
   // A special type for array index should have been
   // created during initial type traversal. Just
   // retrieve that type id.
   ArrayInfo.IndexType = BDebug.getArrayIndexTypeId();
-
-  // Get the number of array elements.
-  // If the array size is 0, set the number of elements as 0.
-  // Otherwise, recursively traverse the base types to
-  // find the element size. The number of elements is
-  // the totoal array size in bits divided by
-  // element size in bits.
-  uint64_t ArraySizeInBits = ATy->getSizeInBits();
-  if (!ArraySizeInBits) {
-    ArrayInfo.Nelems = 0;
-  } else {
-    uint32_t BaseTypeSize = BaseType->getSizeInBits();
-    while (!BaseTypeSize) {
-      const auto *DDTy = cast<DIDerivedType>(BaseType);
-      BaseType = DDTy->getBaseType().resolve();
-      assert(BaseType);
-      BaseTypeSize = BaseType->getSizeInBits();
-    }
-    ArrayInfo.Nelems = ATy->getSizeInBits() / BaseTypeSize;
-  }
 }
 
 void BTFTypeArray::emitType(MCStreamer &OS) {
   BTFTypeBase::emitType(OS);
   OS.EmitIntValue(ArrayInfo.ElemType, 4);
   OS.EmitIntValue(ArrayInfo.IndexType, 4);
   OS.EmitIntValue(ArrayInfo.Nelems, 4);
 }
void BTFDebug::visitStructType(const DICompositeType *CTy, bool IsStruct,
   TypeId = addType(std::move(TypeEntry), CTy);
 
   // Visit all struct members.
   for (const auto *Element : Elements)
     visitTypeEntry(cast<DIDerivedType>(Element));
 }
 
 void BTFDebug::visitArrayType(const DICompositeType *CTy, uint32_t &TypeId) {
-  auto TypeEntry = llvm::make_unique<BTFTypeArray>(CTy);
-  TypeId = addType(std::move(TypeEntry), CTy);
+  // Visit array element type.
+  uint32_t ElemTypeId;
+  visitTypeEntry(CTy->getBaseType().resolve(), ElemTypeId);
+
+  if (!CTy->getSizeInBits()) {
+    auto TypeEntry = llvm::make_unique<BTFTypeArray>(ElemTypeId, 0);
+    ElemTypeId = addType(std::move(TypeEntry), CTy);
+  } else {
+    // Visit array dimensions.
+    DINodeArray Elements = CTy->getElements();
+    for (int I = Elements.size() - 1; I >= 0; --I) {
+      if (auto *Element = dyn_cast_or_null<DINode>(Elements[I]))
+        if (Element->getTag() == dwarf::DW_TAG_subrange_type) {
+          const DISubrange *SR = cast<DISubrange>(Element);
+          auto *CI = SR->getCount().dyn_cast<ConstantInt *>();
+          int64_t Count = CI->getSExtValue();
+
+          auto TypeEntry = llvm::make_unique<BTFTypeArray>(ElemTypeId, Count);
+          if (I == 0)
+            ElemTypeId = addType(std::move(TypeEntry), CTy);
+          else
+            ElemTypeId = addType(std::move(TypeEntry));
+        }
+    }
+  }
+
+  // The array TypeId is the type id of the outermost dimension.
+  TypeId = ElemTypeId;
 
   // The IR does not have a type for array index while BTF wants one.
   // So create an array index type if there is none.
   if (!ArrayIndexTypeId) {
     auto TypeEntry = llvm::make_unique<BTFTypeInt>(dwarf::DW_ATE_unsigned, 32,
                                                    0, "__ARRAY_SIZE_TYPE__");
     ArrayIndexTypeId = addType(std::move(TypeEntry));
   }
-
-  // Visit array element type.
-  visitTypeEntry(CTy->getBaseType().resolve());
 }
 
 void BTFDebug::visitEnumType(const DICompositeType *CTy, uint32_t &TypeId) {
   DINodeArray Elements = CTy->getElements();
   uint32_t VLen = Elements.size();
   if (VLen > BTF::MAX_VLEN)
     return;
 

test/CodeGen/BPF/BTF/array-1d-char.ll

 ; CHECK-NEXT:        .short  60319                   # 0xeb9f
 ; CHECK-NEXT:        .byte   1
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   56
 ; CHECK-NEXT:        .long   56
 ; CHECK-NEXT:        .long   26
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 1)
+; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 1)
+; CHECK-NEXT:        .long   16777216                # 0x1000000
+; CHECK-NEXT:        .long   1
+; CHECK-NEXT:        .long   16777224                # 0x1000008
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 2)
 ; CHECK-NEXT:        .long   50331648                # 0x3000000
 ; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   1
 ; CHECK-NEXT:        .long   3
-; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   10
-; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 2)
+; CHECK-NEXT:        .long   6                       # BTF_KIND_INT(id = 3)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   21                      # BTF_KIND_INT(id = 3)
-; CHECK-NEXT:        .long   16777216                # 0x1000000
-; CHECK-NEXT:        .long   1
-; CHECK-NEXT:        .long   16777224                # 0x1000008
 ; CHECK-NEXT:        .byte   0                       # string offset=0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=1
+; CHECK-NEXT:        .ascii  "char"                  # string offset=1
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "char"                  # string offset=21
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=6
 ; CHECK-NEXT:        .byte   0
 
 !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
 !1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
 !2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
 !3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
 !4 = !{}
 !5 = !{!0}
 !6 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, size: 80, elements: !8)
 !7 = !DIBasicType(name: "char", size: 8, encoding: DW_ATE_signed_char)
 !8 = !{!9}
 !9 = !DISubrange(count: 10)
 !10 = !{i32 2, !"Dwarf Version", i32 4}
 !11 = !{i32 2, !"Debug Info Version", i32 3}
 !12 = !{i32 1, !"wchar_size", i32 4}
 !13 = !{!"clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)"}

test/CodeGen/BPF/BTF/array-1d-int.ll

 ; CHECK-NEXT:        .short  60319                   # 0xeb9f
 ; CHECK-NEXT:        .byte   1
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   56
 ; CHECK-NEXT:        .long   56
 ; CHECK-NEXT:        .long   25
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 1)
+; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 1)
+; CHECK-NEXT:        .long   16777216                # 0x1000000
+; CHECK-NEXT:        .long   4
+; CHECK-NEXT:        .long   16777248                # 0x1000020
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 2)
 ; CHECK-NEXT:        .long   50331648                # 0x3000000
 ; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   1
 ; CHECK-NEXT:        .long   3
-; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   10
-; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 2)
+; CHECK-NEXT:        .long   5                       # BTF_KIND_INT(id = 3)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   21                      # BTF_KIND_INT(id = 3)
-; CHECK-NEXT:        .long   16777216                # 0x1000000
-; CHECK-NEXT:        .long   4
-; CHECK-NEXT:        .long   16777248                # 0x1000020
 ; CHECK-NEXT:        .byte   0                       # string offset=0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=1
+; CHECK-NEXT:        .ascii  "int"                   # string offset=1
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "int"                   # string offset=21
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=5
 ; CHECK-NEXT:        .byte   0
 
 !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
 !1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
 !2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
 !3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
 !4 = !{}
 !5 = !{!0}
 !6 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, size: 320, elements: !8)
 !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
 !8 = !{!9}
 !9 = !DISubrange(count: 10)
 !10 = !{i32 2, !"Dwarf Version", i32 4}
 !11 = !{i32 2, !"Debug Info Version", i32 3}
 !12 = !{i32 1, !"wchar_size", i32 4}
 !13 = !{!"clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)"}

test/CodeGen/BPF/BTF/array-2d-int.ll

 !llvm.ident = !{!13}
 
 ; CHECK:             .section        .BTF,"",@progbits
 ; CHECK-NEXT:        .short  60319                   # 0xeb9f
 ; CHECK-NEXT:        .byte   1
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   56
-; CHECK-NEXT:        .long   56
+; CHECK-NEXT:        .long   80
+; CHECK-NEXT:        .long   80
 ; CHECK-NEXT:        .long   25
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 1)
+; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 1)
+; CHECK-NEXT:        .long   16777216                # 0x1000000
+; CHECK-NEXT:        .long   4
+; CHECK-NEXT:        .long   16777248                # 0x1000020
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 2)
+; CHECK-NEXT:        .long   50331648                # 0x3000000
+; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   1
+; CHECK-NEXT:        .long   4
+; CHECK-NEXT:        .long   10
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 3)
 ; CHECK-NEXT:        .long   50331648                # 0x3000000
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   3
 ; CHECK-NEXT:        .long   2
-; CHECK-NEXT:        .long   100
-; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 2)
-; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
-; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   21                      # BTF_KIND_INT(id = 3)
+; CHECK-NEXT:        .long   10
+; CHECK-NEXT:        .long   5                       # BTF_KIND_INT(id = 4)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
-; CHECK-NEXT:        .long   16777248                # 0x1000020
+; CHECK-NEXT:        .long   32                      # 0x20
 ; CHECK-NEXT:        .byte   0                       # string offset=0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=1
+; CHECK-NEXT:        .ascii  "int"                   # string offset=1
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "int"                   # string offset=21
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=5
 ; CHECK-NEXT:        .byte   0
 
 !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
 !1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 1, type: !6, isLocal: false, isDefinition: true)
 !2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
 !3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
 !4 = !{}
 !5 = !{!0}
 !6 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, size: 3200, elements: !8)
 !7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
 !8 = !{!9, !9}
 !9 = !DISubrange(count: 10)
 !10 = !{i32 2, !"Dwarf Version", i32 4}
 !11 = !{i32 2, !"Debug Info Version", i32 3}
 !12 = !{i32 1, !"wchar_size", i32 4}
 !13 = !{!"clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)"}

test/CodeGen/BPF/BTF/array-size-0.ll

 ; CHECK-NEXT:        .short  60319                   # 0xeb9f
 ; CHECK-NEXT:        .byte   1
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   52
 ; CHECK-NEXT:        .long   52
 ; CHECK-NEXT:        .long   23
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 1)
+; CHECK-NEXT:        .long   1                       # BTF_KIND_STRUCT(id = 1)
+; CHECK-NEXT:        .long   67108864                # 0x4000000
+; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 2)
 ; CHECK-NEXT:        .long   50331648                # 0x3000000
 ; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   1
 ; CHECK-NEXT:        .long   3
-; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 2)
+; CHECK-NEXT:        .long   3                       # BTF_KIND_INT(id = 3)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   21                      # BTF_KIND_STRUCT(id = 3)
-; CHECK-NEXT:        .long   67108864                # 0x4000000
-; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .byte   0                       # string offset=0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=1
+; CHECK-NEXT:        .byte   116                     # string offset=1
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .byte   116                     # string offset=21
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=3
 ; CHECK-NEXT:        .byte   0
 
 !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
 !1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 2, type: !6, isLocal: false, isDefinition: true)
 !2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
 !3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
 !4 = !{}
 !5 = !{!0}
 !6 = !DICompositeType(tag: DW_TAG_array_type, baseType: !7, elements: !8)
 !7 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "t", file: !3, line: 1, elements: !4)
 !8 = !{!9}
 !9 = !DISubrange(count: 10)
 !10 = !{i32 2, !"Dwarf Version", i32 4}
 !11 = !{i32 2, !"Debug Info Version", i32 3}
 !12 = !{i32 1, !"wchar_size", i32 4}
 !13 = !{!"clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)"}

test/CodeGen/BPF/BTF/array-typedef.ll

 ; CHECK-NEXT:        .short  60319                   # 0xeb9f
 ; CHECK-NEXT:        .byte   1
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .long   24
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   80
 ; CHECK-NEXT:        .long   80
 ; CHECK-NEXT:        .long   45
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 1)
-; CHECK-NEXT:        .long   50331648                # 0x3000000
-; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   3
+; CHECK-NEXT:        .long   1                       # BTF_KIND_TYPEDEF(id = 1)
+; CHECK-NEXT:        .long   134217728               # 0x8000000
 ; CHECK-NEXT:        .long   2
-; CHECK-NEXT:        .long   10
-; CHECK-NEXT:        .long   1                       # BTF_KIND_INT(id = 2)
+; CHECK-NEXT:        .long   7                       # BTF_KIND_TYPEDEF(id = 2)
+; CHECK-NEXT:        .long   134217728               # 0x8000000
+; CHECK-NEXT:        .long   3
+; CHECK-NEXT:        .long   12                      # BTF_KIND_INT(id = 3)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   21                      # BTF_KIND_TYPEDEF(id = 3)
-; CHECK-NEXT:        .long   134217728               # 0x8000000
-; CHECK-NEXT:        .long   4
-; CHECK-NEXT:        .long   27                      # BTF_KIND_TYPEDEF(id = 4)
-; CHECK-NEXT:        .long   134217728               # 0x8000000
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 4)
+; CHECK-NEXT:        .long   50331648                # 0x3000000
+; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   1
 ; CHECK-NEXT:        .long   5
-; CHECK-NEXT:        .long   32                      # BTF_KIND_INT(id = 5)
+; CHECK-NEXT:        .long   10
+; CHECK-NEXT:        .long   25                      # BTF_KIND_INT(id = 5)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
 ; CHECK-NEXT:        .byte   0                       # string offset=0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=1
+; CHECK-NEXT:        .ascii  "__int"                 # string offset=1
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "__int"                 # string offset=21
+; CHECK-NEXT:        .ascii  "_int"                  # string offset=7
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "_int"                  # string offset=27
+; CHECK-NEXT:        .ascii  "unsigned int"          # string offset=12
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "unsigned int"          # string offset=32
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=25
 ; CHECK-NEXT:        .byte   0
 
 !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
 !1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 3, type: !6, isLocal: false, isDefinition: true)
 !2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, producer: "clang version 8.0.0 (trunk 345296) (llvm/trunk 345297)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !5, nameTableKind: None)
 !3 = !DIFile(filename: "t.c", directory: "/home/yhs/tmp")
 !4 = !{}
 !5 = !{!0}

test/CodeGen/BPF/BTF/static-var-zerolen-array.ll

 ; CHECK-NEXT:        .long   8
 ; CHECK-NEXT:        .long   55
 ; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   0                       # 0x0
 ; CHECK-NEXT:        .long   57
 ; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   32                      # 0x20
 ; CHECK-NEXT:        .long   59
-; CHECK-NEXT:        .long   6
+; CHECK-NEXT:        .long   7
 ; CHECK-NEXT:        .long   64                      # 0x40
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 6)
+; CHECK-NEXT:        .long   61                      # BTF_KIND_INT(id = 6)
+; CHECK-NEXT:        .long   16777216                # 0x1000000
+; CHECK-NEXT:        .long   1
+; CHECK-NEXT:        .long   16777224                # 0x1000008
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 7)
 ; CHECK-NEXT:        .long   50331648                # 0x3000000
 ; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   6
 ; CHECK-NEXT:        .long   8
-; CHECK-NEXT:        .long   7
 ; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   61                      # BTF_KIND_INT(id = 7)
+; CHECK-NEXT:        .long   66                      # BTF_KIND_INT(id = 8)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   81                      # BTF_KIND_INT(id = 8)
-; CHECK-NEXT:        .long   16777216                # 0x1000000
-; CHECK-NEXT:        .long   1
-; CHECK-NEXT:        .long   16777224                # 0x1000008
 ; CHECK-NEXT:        .long   86                      # BTF_KIND_VAR(id = 9)
 ; CHECK-NEXT:        .long   234881024               # 0xe000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   89                      # BTF_KIND_DATASEC(id = 10)
 ; CHECK-NEXT:        .long   251658241               # 0xf000001
 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   9

 ; CHECK-NEXT:        .byte   116                     # string offset=53
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .byte   97                      # string offset=55
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .byte   98                      # string offset=57
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .byte   99                      # string offset=59
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=61
+; CHECK-NEXT:        .ascii  "char"                  # string offset=61
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "char"                  # string offset=81
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=66
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .ascii  "sv"                    # string offset=86
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .ascii  ".data"                 # string offset=89
 ; CHECK-NEXT:        .byte   0
 
 attributes #0 = { norecurse nounwind "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="true" "no-frame-pointer-elim-non-leaf" "no-infs-fp-math"="false" "no-jump-tables"="false" "no-nans-fp-math"="false" "no-signed-zeros-fp-math"="false" "no-trapping-math"="false" "stack-protector-buffer-size"="8" "unsafe-fp-math"="false" "use-soft-float"="false" }
 

test/CodeGen/BPF/BTF/union-array-typedef.ll

 ; CHECK-NEXT:        .long   0
 ; CHECK-NEXT:        .long   120
 ; CHECK-NEXT:        .long   120
 ; CHECK-NEXT:        .long   41
 ; CHECK-NEXT:        .long   1                       # BTF_KIND_UNION(id = 1)
 ; CHECK-NEXT:        .long   83886082                # 0x5000002
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   3
-; CHECK-NEXT:        .long   2
-; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   3
+; CHECK-NEXT:        .long   0                       # 0x0
 ; CHECK-NEXT:        .long   5
 ; CHECK-NEXT:        .long   5
-; CHECK-NEXT:        .long   0
-; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 2)
+; CHECK-NEXT:        .long   0                       # 0x0
+; CHECK-NEXT:        .long   7                       # BTF_KIND_INT(id = 2)
+; CHECK-NEXT:        .long   16777216                # 0x1000000
+; CHECK-NEXT:        .long   1
+; CHECK-NEXT:        .long   16777224                # 0x1000008
+; CHECK-NEXT:        .long   0                       # BTF_KIND_ARRAY(id = 3)
 ; CHECK-NEXT:        .long   50331648                # 0x3000000
 ; CHECK-NEXT:        .long   0
+; CHECK-NEXT:        .long   2
 ; CHECK-NEXT:        .long   4
-; CHECK-NEXT:        .long   3
 ; CHECK-NEXT:        .long   4
-; CHECK-NEXT:        .long   7                       # BTF_KIND_INT(id = 3)
+; CHECK-NEXT:        .long   12                      # BTF_KIND_INT(id = 4)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   32                      # 0x20
-; CHECK-NEXT:        .long   27                      # BTF_KIND_INT(id = 4)
-; CHECK-NEXT:        .long   16777216                # 0x1000000
-; CHECK-NEXT:        .long   1
-; CHECK-NEXT:        .long   16777224                # 0x1000008
 ; CHECK-NEXT:        .long   32                      # BTF_KIND_TYPEDEF(id = 5)
 ; CHECK-NEXT:        .long   134217728               # 0x8000000
 ; CHECK-NEXT:        .long   6
 ; CHECK-NEXT:        .long   37                      # BTF_KIND_INT(id = 6)
 ; CHECK-NEXT:        .long   16777216                # 0x1000000
 ; CHECK-NEXT:        .long   4
 ; CHECK-NEXT:        .long   16777248                # 0x1000020
 ; CHECK-NEXT:        .byte   0                       # string offset=0
 ; CHECK-NEXT:        .byte   116                     # string offset=1
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .byte   109                     # string offset=3
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .byte   110                     # string offset=5
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=7
+; CHECK-NEXT:        .ascii  "char"                  # string offset=7
 ; CHECK-NEXT:        .byte   0
-; CHECK-NEXT:        .ascii  "char"                  # string offset=27
+; CHECK-NEXT:        .ascii  "__ARRAY_SIZE_TYPE__"   # string offset=12
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .ascii  "_int"                  # string offset=32
 ; CHECK-NEXT:        .byte   0
 ; CHECK-NEXT:        .ascii  "int"                   # string offset=37
 ; CHECK-NEXT:        .byte   0
 
 !0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
 !1 = distinct !DIGlobalVariable(name: "a", scope: !2, file: !3, line: 2, type: !6, isLocal: false, isDefinition: true)