Fix crash when linking metadata with ODR type uniquing

[tejohnson]

Summary

With DebugTypeODRUniquing enabled, during IR linking debug metadata
in the destination module may be reached from the source module.
This means that ConstantAsMetadata nodes (e.g. on DITemplateValueParameter)
may contain a value the destination module. When trying to map such
metadata nodes, we will attempt to map a GV already in the dest module.
linkGlobalValueProto will end up with a source GV that is the same as
the dest GV as well as the new GV. Trying to access the TypeMap for the
source GV type, which is actually a dest GV type, hits an assertion
since it appears that we have mapped into the source module (because the
type is the value not a key into the map).

Detect that we don't need to access the TypeMap in this case, since
there is no need to create a bitcast from the new GV to the source GV
type as they GV are the same.

Fixes PR35722.

[mehdi_amini]

lib/Linker/IRMover.cpp

957–962

Might be worth a comment?

test/ThinLTO/X86/Inputs/dicompositetype-unique2.ll

57

Can all the metadata input be minimized?

[tejohnson]

test/ThinLTO/X86/Inputs/dicompositetype-unique2.ll

57

The new version I'm going to upload minimizes it as much as I could while reproducing the assert.

[tejohnson]

Address comments.

[tejohnson]

Ping

[mehdi_amini]

The test still seems complex to me (do you need all the IR types? The code in the functions? And all these metadatas and metadata fields?

Otherwise it seems fine, can you backport to the LLVM 6 release branch?

[tejohnson]

In D41624#971298, @mehdi_amini wrote:

The test still seems complex to me (do you need all the IR types? The code in the functions? And all these metadatas and metadata fields?

Yes unfortunately. I tried various other ways to reduce it, without luck.

Otherwise it seems fine, can you backport to the LLVM 6 release branch?

Will do.

lib/Linker/IRMover.cpp

if (const Comdat *SC = SGV->getComdat()) {
       }
     }
   }
 
   if (!ShouldLink && ForAlias)
     NewGV->setLinkage(GlobalValue::InternalLinkage);
 
   Constant *C = NewGV;
-  if (DGV)
+  // Only create a bitcast if necessary. In particular, with
+  // DebugTypeODRUniquing we may reach metadata in the destination module
+  // containing a GV from the source module, in which case SGV will be
+  // the same as DGV and NewGV, and TypeMap.get() will assert since it
+  // assumes it is being invoked on a type in the source module.
+  if (DGV && NewGV != SGV)
     C = ConstantExpr::getBitCast(NewGV, TypeMap.get(SGV->getType()));
 
   if (DGV && NewGV != DGV) {
     DGV->replaceAllUsesWith(ConstantExpr::getBitCast(NewGV, DGV->getType()));
     DGV->eraseFromParent();
   }
 
   return C;

test/ThinLTO/X86/Inputs/dicompositetype-unique2.ll

+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-scei-ps4"
+
+%struct.CFVS = type { %struct.Vec }
+%struct.Vec = type { i8 }
+%struct.S = type { i8 }
+
+define void @_ZN4CFVSD2Ev(%struct.CFVS* %this) unnamed_addr align 2 !dbg !8 {
+entry:
+  %this.addr = alloca %struct.CFVS*, align 8
+  store %struct.CFVS* %this, %struct.CFVS** %this.addr, align 8
+  %this1 = load %struct.CFVS*, %struct.CFVS** %this.addr, align 8
+  %m_val = getelementptr inbounds %struct.CFVS, %struct.CFVS* %this1, i32 0, i32 0
+  ret void
+}
+
+declare dereferenceable(1) %struct.S* @_Z3Getv()
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 (trunk 321360) (llvm/trunk 321359)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "bz188598-b.cpp", directory: "")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!8 = distinct !DISubprogram(name: "~CFVS", linkageName: "_ZN4CFVSD2Ev", scope: !9, file: !1, line: 2, type: !28, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, unit: !0, declaration: !27, variables: !2)
+!9 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "CFVS", file: !10, line: 7, size: 8, elements: !11, identifier: "_ZTS4CFVS")
+!10 = !DIFile(filename: "./bz188598.h", directory: "")
+!11 = !{!12, !27}
+!12 = !DIDerivedType(tag: DW_TAG_member, name: "m_val", scope: !9, file: !10, line: 9, baseType: !13, size: 8)
+!13 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Vec<&Get>", file: !10, line: 4, size: 8, elements: !14, templateParams: !19, identifier: "_ZTS3VecIXadL_Z3GetvEEE")
+!14 = !{!35}
+!19 = !{!20}
+!20 = !DITemplateValueParameter(name: "F", type: !21, value: %struct.S* ()* @_Z3Getv)
+!21 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !22, size: 64)
+!22 = !DIDerivedType(tag: DW_TAG_typedef, name: "Func", file: !10, line: 2, baseType: !23)
+!23 = !DISubroutineType(types: !24)
+!24 = !{!35}
+!27 = !DISubprogram(name: "~CFVS", scope: !9, file: !10, line: 8, type: !28, isLocal: false, isDefinition: false, scopeLine: 8, flags: DIFlagPrototyped, isOptimized: false)
+!28 = !DISubroutineType(types: !29)
+!29 = !{null, !30}
+!30 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !9, size: 64, flags: DIFlagArtificial | DIFlagObjectPointer)
+!35 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)

test/ThinLTO/X86/dicompositetype-unique2.ll

+; RUN: opt -module-summary -o %t1.bc %s
+; RUN: opt -module-summary -o %t2.bc %S/Inputs/dicompositetype-unique2.ll
+; RUN: llvm-lto --thinlto-action=run %t1.bc %t2.bc -thinlto-save-temps=%t3.
+; RUN: llvm-dis %t3.0.3.imported.bc -o - | FileCheck %s
+; RUN: llvm-lto2 run %t1.bc %t2.bc -o %t --save-temps \
+; RUN: -r %t1.bc,_ZN1CD2Ev,pl \
+; RUN: -r %t1.bc,_ZN4CFVSD2Ev,l \
+; RUN: -r %t1.bc,_Z3Getv,l \
+; RUN: -r %t2.bc,_ZN4CFVSD2Ev,pl \
+; RUN: -r %t2.bc,_Z3Getv,l
+; RUN: llvm-dis %t.1.3.import.bc -o - | FileCheck %s
+
+; Only llvm-lto2 adds the dso_local keyword, hence the {{.*}}
+; CHECK: define available_externally{{.*}} void @_ZN4CFVSD2Ev
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-scei-ps4"
+
+%class.C = type <{ i32 (...)**, %class.A, %struct.CFVS, [6 x i8] }>
+%class.A = type { %struct.Vec }
+%struct.Vec = type { i8 }
+%struct.CFVS = type { %struct.Vec }
+%struct.S = type { i8 }
+
+define void @_ZN1CD2Ev(%class.C* %this) unnamed_addr align 2 !dbg !8 {
+entry:
+  %this.addr = alloca %class.C*, align 8
+  %this1 = load %class.C*, %class.C** %this.addr, align 8
+  %m = getelementptr inbounds %class.C, %class.C* %this1, i32 0, i32 2
+  call void @_ZN4CFVSD2Ev(%struct.CFVS* %m), !dbg !50
+  ret void
+}
+
+declare void @_ZN4CFVSD2Ev(%struct.CFVS*) unnamed_addr
+
+declare dereferenceable(1) %struct.S* @_Z3Getv()
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!3, !4, !5, !6}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 6.0.0 (trunk 321360) (llvm/trunk 321359)", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, enums: !2)
+!1 = !DIFile(filename: "bz188598-a.cpp", directory: ".")
+!2 = !{}
+!3 = !{i32 2, !"Dwarf Version", i32 4}
+!4 = !{i32 2, !"Debug Info Version", i32 3}
+!5 = !{i32 1, !"wchar_size", i32 2}
+!6 = !{i32 7, !"PIC Level", i32 2}
+!8 = distinct !DISubprogram(name: "~C", linkageName: "_ZN1CD2Ev", scope: !9, file: !1, line: 9, type: !47, isLocal: false, isDefinition: true, scopeLine: 9, flags: DIFlagPrototyped, isOptimized: false, unit: !0, declaration: !46, variables: !2)
+!9 = distinct !DICompositeType(tag: DW_TAG_class_type, name: "C", file: !1, line: 5, size: 128, elements: !10, vtableHolder: !9, identifier: "_ZTS1C")
+!10 = !{!38, !46}
+!15 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "Vec<&Get>", file: !16, line: 4, size: 8, elements: !17, templateParams: !22, identifier: "_ZTS3VecIXadL_Z3GetvEEE")
+!16 = !DIFile(filename: "./bz188598.h", directory: ".")
+!17 = !{!55}
+!22 = !{!23}
+!23 = !DITemplateValueParameter(name: "F", type: !24, value: %struct.S* ()* @_Z3Getv)
+!24 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !25, size: 64)
+!25 = !DIDerivedType(tag: DW_TAG_typedef, name: "Func", file: !16, line: 2, baseType: !26)
+!26 = !DISubroutineType(types: !27)
+!27 = !{!55}
+!38 = !DIDerivedType(tag: DW_TAG_member, name: "m", scope: !9, file: !1, line: 7, baseType: !39, size: 8, offset: 72)
+!39 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "CFVS", file: !16, line: 7, size: 8, elements: !40, identifier: "_ZTS4CFVS")
+!40 = !{!41}
+!41 = !DIDerivedType(tag: DW_TAG_member, name: "m_val", scope: !39, file: !16, line: 9, baseType: !15, size: 8)
+!46 = !DISubprogram(name: "~C", scope: !9, file: !1, line: 6, type: !47, isLocal: false, isDefinition: false, scopeLine: 6, containingType: !9, virtuality: DW_VIRTUALITY_virtual, virtualIndex: 0, flags: DIFlagPrototyped, isOptimized: false)
+!47 = !DISubroutineType(types: !48)
+!48 = !{!55}
+!50 = !DILocation(line: 9, scope: !51)
+!51 = distinct !DILexicalBlock(scope: !8, file: !1, line: 9)
+!55 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)