[COFF] Fix reading variable-length encoded records

[aganea]

Summary

While reading Codeview records which contain variable-length encoded integers,
such as LF_BCLASS, LF_ENUMERATE, LF_MEMBER, LF_VBCLASS or LF_IVBCLASS,
the record's size would be improperly calculated in cases where the value was
indeed variable-length (>= LF_NUMERIC). This caused a bad alignement on the
next record, which would/might crash later on.

[rnk]

test/DebugInfo/COFF/enum_var.ll

1

I don't think this test exercises the fix. Only type stream merging and LLD exercise type index discovery.

[zturner]

We have a unit test called TypeIndexDiscoveryTest. Could go there.

[aganea]

My bad - I should have tested without the patch. Updated following @zturner's suggestion.

llvm/lib/DebugInfo/CodeView/TypeIndexDiscovery.cpp

       8,  // LF_UQUADWORD
   };
 
-  return Sizes[N - LF_NUMERIC];
+  return 2 + Sizes[N - LF_NUMERIC];
 }
 
 static inline uint32_t getCStringLength(ArrayRef<uint8_t> Data) {

     Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
     break;
   case SymbolKind::S_REGISTER:
-    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type;
+    Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type
     break;
   case SymbolKind::S_CONSTANT:
     Refs.push_back({TiRefKind::TypeRef, 0, 1}); // Type

test/DebugInfo/COFF/enum_var.ll

+; RUN: llc < %s -filetype=obj | llvm-readobj - -codeview | FileCheck %s
+
+; // enum.cpp
+; enum E : unsigned long long { BLAH = -1, BLAH_2 = 0x123456789ABC, BLAH_3 = 1, BLAH_4 = 0xABCDEF };
+; E e;
+; // compile with: clang++.exe enum.cpp -c -g -gcodeview -emit-llvm -S
+
+; CHECK:     CodeViewTypes [
+; CHECK:       FieldList (0x1000) {
+; CHECK-NEXT:    TypeLeafKind: LF_FIELDLIST (0x1203)
+; CHECK-NEXT:    Enumerator {
+; CHECK-NEXT:      TypeLeafKind: LF_ENUMERATE (0x1502)
+; CHECK-NEXT:      AccessSpecifier: Public (0x3)
+; CHECK-NEXT:      EnumValue: 18446744073709551615
+; CHECK-NEXT:      Name: BLAH
+; CHECK-NEXT:    }
+; CHECK-NEXT:    Enumerator {
+; CHECK-NEXT:      TypeLeafKind: LF_ENUMERATE (0x1502)
+; CHECK-NEXT:      AccessSpecifier: Public (0x3)
+; CHECK-NEXT:      EnumValue: 20015998343868
+; CHECK-NEXT:      Name: BLAH_2
+; CHECK-NEXT:    }
+; CHECK-NEXT:    Enumerator {
+; CHECK-NEXT:      TypeLeafKind: LF_ENUMERATE (0x1502)
+; CHECK-NEXT:      AccessSpecifier: Public (0x3)
+; CHECK-NEXT:      EnumValue: 1
+; CHECK-NEXT:      Name: BLAH_3
+; CHECK-NEXT:    }
+; CHECK-NEXT:    Enumerator {
+; CHECK-NEXT:      TypeLeafKind: LF_ENUMERATE (0x1502)
+; CHECK-NEXT:      AccessSpecifier: Public (0x3)
+; CHECK-NEXT:      EnumValue: 11259375
+; CHECK-NEXT:      Name: BLAH_4
+; CHECK-NEXT:    }
+; CHECK-NEXT:  }
+; CHECK-NEXT:  Enum (0x1001) {
+; CHECK-NEXT:    TypeLeafKind: LF_ENUM (0x1507)
+; CHECK-NEXT:    NumEnumerators: 4
+; CHECK-NEXT:    Properties [ (0x200)
+; CHECK-NEXT:      HasUniqueName (0x200)
+; CHECK-NEXT:    ]
+; CHECK-NEXT:    UnderlyingType: unsigned __int64 (0x23)
+; CHECK-NEXT:    FieldListType: <field list> (0x1000)
+; CHECK-NEXT:    Name: E
+; CHECK-NEXT:    LinkageName: .?AW4E@@
+; CHECK-NEXT:  }
+
+; ModuleID = 'enum.cpp'
+source_filename = "enum.cpp"
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc19.0.24215"
+
+@"?e@@3W4E@@A" = dso_local global i64 0, align 8, !dbg !0
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!13, !14, !15, !16}
+!llvm.ident = !{!17}
+
+!0 = !DIGlobalVariableExpression(var: !1, expr: !DIExpression())
+!1 = distinct !DIGlobalVariable(name: "e", linkageName: "?e@@3W4E@@A", scope: !2, file: !3, line: 2, type: !5, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !3, producer: "clang version 7.0.0 (trunk 328567)", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !4, globals: !12)
+!3 = !DIFile(filename: "enum.cpp", directory: "F:\5Csvn\5Cllvm\5Ctest\5CDebugInfo\5CCOFF\5Ctest_enum", checksumkind: CSK_MD5, checksum: "05f78dfb7eedd016656ccbc2da244c0f")
+!4 = !{!5}
+!5 = !DICompositeType(tag: DW_TAG_enumeration_type, name: "E", file: !3, line: 1, baseType: !6, size: 64, flags: DIFlagFixedEnum, elements: !7, identifier: ".?AW4E@@")
+!6 = !DIBasicType(name: "long long unsigned int", size: 64, encoding: DW_ATE_unsigned)
+!7 = !{!8, !9, !10, !11}
+!8 = !DIEnumerator(name: "BLAH", value: 18446744073709551615, isUnsigned: true)
+!9 = !DIEnumerator(name: "BLAH_2", value: 20015998343868, isUnsigned: true)
+!10 = !DIEnumerator(name: "BLAH_3", value: 1, isUnsigned: true)
+!11 = !DIEnumerator(name: "BLAH_4", value: 11259375, isUnsigned: true)
+!12 = !{!0}
+!13 = !{i32 2, !"CodeView", i32 1}
+!14 = !{i32 2, !"Debug Info Version", i32 3}
+!15 = !{i32 1, !"wchar_size", i32 2}
+!16 = !{i32 7, !"PIC Level", i32 2}
+!17 = !{!"clang version 7.0.0 (trunk 328567)"}