Fix faulty assertion in debug info

It appears the code uses nullptr to represent a void type in debug metadata,
which led to an assertion failure when building DeltaAlgorithm.cpp with a
self-hosted clang on Windows.

I'm not sure why/if the problem was Windows-specific.

Fixes bug https://bugs.llvm.org/show_bug.cgi?id=35543

Differential Revision: https://reviews.llvm.org/D41264

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@321122 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/AsmPrinter/DebugHandlerBase.cpp

@@ -163,7 +163,8 @@ uint64_t DebugHandlerBase::getBaseTypeSize(const DITypeRef TyRef) {
 
   DIType *BaseType = DDTy->getBaseType().resolve();
 
-  assert(BaseType && "Unexpected invalid base type");
+  if (!BaseType)
+    return 0;
 
   // If this is a derived type, go ahead and get the base type, unless it's a
   // reference then it's just the size of the field. Pointer types have no need

lib/CodeGen/AsmPrinter/DwarfUnit.cpp

@@ -1391,7 +1391,8 @@ void DwarfUnit::constructMemberDIE(DIE &Buffer, const DIDerivedType *DT) {
   if (!Name.empty())
     addString(MemberDie, dwarf::DW_AT_name, Name);
 
-  addType(MemberDie, resolve(DT->getBaseType()));
+  if (DIType *Resolved = resolve(DT->getBaseType()))
+    addType(MemberDie, Resolved);
 
   addSourceLine(MemberDie, DT);
 

test/DebugInfo/void-typedef.ll

@@ -0,0 +1,88 @@
+; Choosing CodeView generates debug metadata for class-scope typedefs that
+; Dwarf would normally omit.  Choosing both CodeView and Dwarf triggered
+; assertion failures and crashes because the Dwarf handler wasn't prepared for
+; those records (in particular, ones with the void type represented by a
+; null pointer).
+;
+; This test was generated with:
+;    clang++ -cc1 -emit-llvm -debug-info-kind=limited -dwarf-version=4 -gcodeview -x c++
+; on the following source code:
+;
+;   class A {
+;     typedef void _Nodeptr;
+;   };
+;   class B {
+;     A FailedTestsCache;
+;     bool m_fn1();
+;   };
+;   bool B::m_fn1() {}
+;
+; CodeView generates a DIDerivedType for the _Nodeptr typedef.
+;
+; RUN: llc %s -o - 2>&1 | FileCheck %s
+; CHECK-NOT: Assertion failed
+
+; ModuleID = 'bug.cpp'
+source_filename = "bug.cpp"
+target datalayout = "e-m:x-p:32:32-i64:64-f80:32-n8:16:32-a:0:32-S32"
+target triple = "i686-pc-windows-msvc"
+
+%class.B = type { %class.A }
+%class.A = type { i8 }
+
+; Function Attrs: noinline nounwind optnone
+define x86_thiscallcc zeroext i1 @"\01?m_fn1@B@@AAE_NXZ"(%class.B* %this) #0 align 2 !dbg !9 {
+entry:
+  %retval = alloca i1, align 1
+  %this.addr = alloca %class.B*, align 4
+  store %class.B* %this, %class.B** %this.addr, align 4
+  call void @llvm.dbg.declare(metadata %class.B** %this.addr, metadata !22, metadata !DIExpression()), !dbg !24
+  %this1 = load %class.B*, %class.B** %this.addr, align 4
+  call void @llvm.trap(), !dbg !25
+  unreachable, !dbg !25
+
+return:                                           ; No predecessors!
+  %0 = load i1, i1* %retval, align 1, !dbg !25
+  ret i1 %0, !dbg !25
+}
+
+; Function Attrs: nounwind readnone speculatable
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: noreturn nounwind
+declare void @llvm.trap() #2
+
+attributes #0 = { noinline nounwind optnone "correctly-rounded-divide-sqrt-fp-math"="false" "disable-tail-calls"="false" "less-precise-fpmad"="false" "no-frame-pointer-elim"="false" "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" "target-features"="+x87" "unsafe-fp-math"="false" "use-soft-float"="false" }
+attributes #1 = { nounwind readnone speculatable }
+attributes #2 = { noreturn nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6, !7}
+!llvm.ident = !{!8}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 ", isOptimized: false, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "<stdin>", directory: "D:\5Csrc\5Cbug", checksumkind: CSK_MD5, checksum: "2216f11c5ddda8c48a6f92a6079ad4b6")
+!2 = !{}
+!3 = !{i32 1, !"NumRegisterParameters", i32 0}
+!4 = !{i32 2, !"Dwarf Version", i32 4}
+!5 = !{i32 2, !"CodeView", i32 1}
+!6 = !{i32 2, !"Debug Info Version", i32 3}
+!7 = !{i32 1, !"wchar_size", i32 2}
+!8 = !{!"clang version 6.0.0 "}
+!9 = distinct !DISubprogram(name: "m_fn1", linkageName: "\01?m_fn1@B@@AAE_NXZ", scope: !11, file: !10, line: 8, type: !18, isLocal: false, isDefinition: true, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false, unit: !0, declaration: !17, variables: !2)
+!10 = !DIFile(filename: "bug.cpp", directory: "D:\5Csrc\5Cbug", checksumkind: CSK_MD5, checksum: "2216f11c5ddda8c48a6f92a6079ad4b6")
+!11 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "B", file: !10, line: 4, size: 8, elements: !12, identifier: ".?AVB@@")
+!12 = !{!13, !17}
+!13 = !DIDerivedType(tag: DW_TAG_member, name: "FailedTestsCache", scope: !11, file: !10, line: 5, baseType: !14, size: 8)
+!14 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "A", file: !10, line: 1, size: 8, elements: !15, identifier: ".?AVA@@")
+!15 = !{!16}
+!16 = !DIDerivedType(tag: DW_TAG_typedef, name: "_Nodeptr", scope: !14, file: !10, line: 2, baseType: null)
+!17 = !DISubprogram(name: "m_fn1", linkageName: "\01?m_fn1@B@@AAE_NXZ", scope: !11, file: !10, line: 6, type: !18, isLocal: false, isDefinition: false, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: false)
+!18 = !DISubroutineType(cc: DW_CC_BORLAND_thiscall, types: !19)
+!19 = !{!20, !21}
+!20 = !DIBasicType(name: "bool", size: 8, encoding: DW_ATE_boolean)
+!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 32, flags: DIFlagArtificial | DIFlagObjectPointer)
+!22 = !DILocalVariable(name: "this", arg: 1, scope: !9, type: !23, flags: DIFlagArtificial | DIFlagObjectPointer)
+!23 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !11, size: 32)
+!24 = !DILocation(line: 0, scope: !9)
+!25 = !DILocation(line: 8, scope: !9)