Fix ThinLTO crash with debug info

[mehdi_amini]

Summary

Because the recent change about ODR type uniquing in the context,
we can reach types defined in another module during IR linking.
This triggered some assertions in case we IR link without starting
from an empty module. To alleviate that, we can self-map metadata
defined in the destination module so that they won't be visited.

[mehdi_amini]

Teresa: work-in-progress, I need to rebase on ToT and cleanup the test.

[tejohnson]

Ping, is this one ready for review? It fixes several ThinLTO debug issues

[mehdi_amini]

Reduce the test case, ready to go!

[mehdi_amini]

Make the test more robust, and add a FileCheck line

[tejohnson]

LGTM with a couple of test case fixes noted below.

test/ThinLTO/X86/crash_debuginfo.ll

8

How are you verifying that bar is imported? Can you check for the inlined add in the body of foo?

10

s/NOt/NOT

[mehdi_amini]

test/ThinLTO/X86/crash_debuginfo.ll

8

The "CHECK-NOT" fires when bar isn't imported (we get an undefined referenced to bar), this relies on the inliner.

[tejohnson]

LGTM

include/llvm/IR/TypeFinder.h

public:
   const_iterator end() const { return StructTypes.end(); }
 
   bool empty() const { return StructTypes.empty(); }
   size_t size() const { return StructTypes.size(); }
   iterator erase(iterator I, iterator E) { return StructTypes.erase(I, E); }
 
   StructType *&operator[](unsigned Idx) { return StructTypes[Idx]; }
 
+  DenseSet<const MDNode *> &getVisitedMetadata() { return VisitedMetadata; }
+
 private:
   /// incorporateType - This method adds the type to the list of used
   /// structures if it's not in there already.
   void incorporateType(Type *Ty);
 
   /// incorporateValue - This method is used to walk operand lists finding types
   /// hiding in constant expressions and other operands that won't be walked in
   /// other ways.  GlobalValues, basic blocks, instructions, and inst operands

lib/Linker/IRMover.cpp

IRMover::IRMover(Module &M) : Composite(M) {
   TypeFinder StructTypes;
   StructTypes.run(M, true);
   for (StructType *Ty : StructTypes) {
     if (Ty->isOpaque())
       IdentifiedStructTypes.addOpaque(Ty);
     else
       IdentifiedStructTypes.addNonOpaque(Ty);
   }
+  // Self-map metadatas in the destination module. This is needed when
+  // DebugTypeODRUniquing is enabled on the LLVMContext, since metadata in the
+  // destination module may be reached from the source module.
+  for (auto *MD : StructTypes.getVisitedMetadata()) {
+    SharedMDs[MD].reset(const_cast<MDNode *>(MD));
+  }
 }
 
 Error IRMover::move(
     std::unique_ptr<Module> Src, ArrayRef<GlobalValue *> ValuesToLink,
     std::function<void(GlobalValue &, ValueAdder Add)> AddLazyFor) {
   IRLinker TheIRLinker(Composite, SharedMDs, IdentifiedStructTypes,
                        std::move(Src), ValuesToLink, std::move(AddLazyFor));
   Error E = TheIRLinker.run();
   Composite.dropTriviallyDeadConstantArrays();
   return E;
 }

test/ThinLTO/X86/Inputs/crash_debuginfo.ll

+; ModuleID = 'test/ThinLTO/X86/Inputs/crash_debuginfo.ll'
+source_filename = "src.bc"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.7.0"
+
+%another_type = type { i32 }
+
+define void @bar(i32 %arg) {
+  %tmp = add i32 %arg, 0, !dbg !7
+  unreachable
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "Apple LLVM version 8.0.0 (clang-800.0.25.1)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2, retainedTypes: !2, globals: !3, imports: !2)
+!1 = !DIFile(filename: "2.cpp", directory: "some_dir")
+!2 = !{}
+!3 = !{!4}
+!4 = distinct !DIGlobalVariable(name: "a_global", linkageName: "a_global", scope: null, line: 52, type: !5, isLocal: true, isDefinition: true, variable: %another_type** undef)
+!5 = !DISubroutineType(types: !2)
+!6 = !{i32 2, !"Debug Info Version", i32 3}
+!7 = distinct !DILocation(line: 728, column: 71, scope: !8, inlinedAt: !14)
+!8 = distinct !DISubprogram(name: "baz", linkageName: "baz", scope: !9, file: !1, line: 726, type: !5, isLocal: false, isDefinition: true, scopeLine: 727, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !10, variables: !11)
+!9 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "some_other_class", scope: !1, file: !1, line: 197, size: 192, align: 64, elements: !2, templateParams: !2, identifier: "some_other_class")
+!10 = !DISubprogram(name: "baz", linkageName: "baz", scope: !9, file: !1, line: 726, type: !5, isLocal: false, isDefinition: false, scopeLine: 726, flags: DIFlagPrototyped, isOptimized: true)
+!11 = !{!12}
+!12 = !DILocalVariable(name: "caster", scope: !8, file: !1, line: 728, type: !13)
+!13 = distinct !DICompositeType(tag: DW_TAG_union_type, scope: !8, file: !1, line: 728, size: 64, align: 64, elements: !2, identifier: "someclass")
+!14 = distinct !DILocation(line: 795, column: 16, scope: !15)
+!15 = distinct !DILexicalBlock(scope: !16, file: !1, line: 794, column: 7)
+!16 = distinct !DISubprogram(name: "operator()", linkageName: "some_special_function", scope: null, file: !1, line: 783, type: !5, isLocal: true, isDefinition: true, scopeLine: 784, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !17, variables: !2)
+!17 = !DISubprogram(name: "operator()", linkageName: "some_special_function", scope: null, file: !1, line: 783, type: !5, isLocal: false, isDefinition: false, scopeLine: 783, flags: DIFlagPrototyped, isOptimized: true)

test/ThinLTO/X86/crash_debuginfo.ll

+; RUN: opt -module-summary -o %t-dst.bc %s
+; RUN: opt -module-summary -o %t-src.bc %p/Inputs/crash_debuginfo.ll
+; RUN: llvm-lto -thinlto -o %t-index %t-dst.bc %t-src.bc
+; RUN: opt -function-import -summary-file %t-index.thinlto.bc %t-dst.bc -o /dev/null
+
+
+
+; ModuleID = 'test/ThinLTO/X86/crash_debuginfo.ll'
+source_filename = "test/ThinLTO/X86/crash_debuginfo.ll"
+target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-apple-macosx10.7.0"
+
+%some_type = type { i32 }
+
+define void @foo() {
+  call void @bar()
+  %tmp47 = add i32 0, 0, !dbg !8
+  unreachable
+}
+
+declare void @bar()
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!7}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "Apple LLVM version 8.0.0 (clang-800.0.24.1)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, imports: !2)
+!1 = !DIFile(filename: "1.cpp", directory: "/another_dir")
+!2 = !{!3}
+!3 = !DIImportedEntity(tag: DW_TAG_imported_declaration, scope: !1, entity: !4, line: 39)
+!4 = distinct !DIGlobalVariable(name: "_", linkageName: "some_global", scope: null, file: !1, line: 20, type: !5, isLocal: true, isDefinition: true, variable: %some_type* undef)
+!5 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "slice_nil", file: !1, line: 13, size: 64, align: 64, elements: !6, identifier: "_ZTSN5boost6python3api9slice_nilE")
+!6 = !{}
+!7 = !{i32 2, !"Debug Info Version", i32 3}
+!8 = distinct !DILocation(line: 728, column: 71, scope: !9, inlinedAt: !16)
+!9 = distinct !DISubprogram(name: "baz", linkageName: "baz", scope: !10, file: !1, line: 726, type: !11, isLocal: false, isDefinition: true, scopeLine: 727, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !12, variables: !13)
+!10 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "some_other_class", file: !1, line: 197, size: 192, align: 64, elements: !6, templateParams: !6, identifier: "some_other_class")
+!11 = !DISubroutineType(types: !6)
+!12 = !DISubprogram(name: "baz", linkageName: "baz", scope: !10, file: !1, line: 726, type: !11, isLocal: false, isDefinition: false, scopeLine: 726, flags: DIFlagPrototyped, isOptimized: true)
+!13 = !{!14}
+!14 = !DILocalVariable(name: "caster", scope: !9, file: !1, line: 728, type: !15)
+!15 = distinct !DICompositeType(tag: DW_TAG_union_type, scope: !9, file: !1, line: 728, size: 64, align: 64, elements: !6, identifier: "someclass")
+!16 = distinct !DILocation(line: 87, column: 9, scope: !17)
+!17 = distinct !DISubprogram(name: "foo", linkageName: "foo", scope: !10, line: 73, type: !11, isLocal: false, isDefinition: true, scopeLine: 74, flags: DIFlagPrototyped, isOptimized: true, unit: !0, declaration: !18, variables: !6)
+!18 = !DISubprogram(name: "foo", linkageName: "foo", scope: !10, file: !1, line: 83, type: !11, isLocal: false, isDefinition: false, scopeLine: 83, flags: DIFlagPrototyped, isOptimized: true)