[ThinLTO] Do not duplicate import a function that is actually defined…

… in the current module (llvm#110064)

Doing so could cause a bug where the linker tries to remap a function
"reimported" from the current module when materializing it, causing a
lookup assert in the type mappings.

llvm/lib/Linker/IRMover.cpp

@@ -595,11 +595,15 @@ Value *IRLinker::materialize(Value *V, bool ForIndirectSymbol) {
   if (!SGV)
     return nullptr;
 
+  // If SGV is from dest, it was already materialized when dest was loaded.
+  if (SGV->getParent() == &DstM)
+    return nullptr;
+
   // When linking a global from other modules than source & dest, skip
   // materializing it because it would be mapped later when its containing
   // module is linked. Linking it now would potentially pull in many types that
   // may not be mapped properly.
-  if (SGV->getParent() != &DstM && SGV->getParent() != SrcM.get())
+  if (SGV->getParent() != SrcM.get())
     return nullptr;
 
   Expected<Constant *> NewProto = linkGlobalValueProto(SGV, ForIndirectSymbol);

llvm/test/ThinLTO/X86/Inputs/ditemplatevalueparameter-remap.ll

@@ -0,0 +1,29 @@
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @_Z8thinlto1v() unnamed_addr {
+  %3 = alloca i64, align 4
+    #dbg_declare(ptr %3, !14, !DIExpression(), !15)
+  ret void
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "B.cpp", directory: ".")
+!2 = !{i32 7, !"Dwarf Version", i32 4}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!10 = distinct !DISubprogram(name: "thinlto1", linkageName: "_Z8thinlto1v", scope: !11, file: !11, line: 8, type: !12, scopeLine: 8, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!11 = !DIFile(filename: "b.cpp", directory: ".")
+!12 = !DISubroutineType(types: !13)
+!13 = !{null}
+!14 = !DILocalVariable(name: "a", arg: 1, scope: !10, file: !11, line: 18, type: !16)
+!15 = !DILocation(line: 18, column: 19, scope: !10)
+!16 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S<&func1>", file: !11, line: 2, size: 8, flags: DIFlagTypePassByValue, elements: !17, templateParams: !18, identifier: "_ZTS1SIXadL_Z5func1vEEE")
+!17 = !{}
+!18 = !{!19}
+!19 = !DITemplateValueParameter(name: "Func", type: !20, value: ptr undef)
+!20 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !12, size: 64)

llvm/test/ThinLTO/X86/ditemplatevalueparameter-remap.ll

@@ -0,0 +1,87 @@
+; https://github.com/llvm/llvm-project/pull/110064
+; This test case checks if thinLTO correctly links metadata values in a specific
+; situation. Assume we are linking module B into module A, where an extern
+; function used in A is defined in B, but the function body has a
+; DITemplateValueParameter referring to another function back in A. The
+; compiler must check this other function is actually coming from A, thus
+; already materialized and does not require remapping. The IR here is modified
+; from the following source code.
+;
+; // A.h
+; template <void (*Func)()>
+; struct S {
+;   void Impl() {
+;     Func();
+;   }
+; };
+;
+; void func1();
+;
+; // A.cpp
+; #include "A.h"
+; __attribute__((weak)) void func1() {}
+; extern void thinlto1();
+; void bar() {
+;   S<func1> s; // Force instantiation of S<func1> in this compilation unit.
+;   s.Impl();
+;   thinlto1();
+; }
+;
+; // B.cpp
+; #include "A.h"
+; void thinlto1() {
+;   S<func1> s;
+; }
+;
+; RUN: opt -module-summary -o %t1.bc %s
+; RUN: opt -module-summary -o %t2.bc %S/Inputs/ditemplatevalueparameter-remap.ll
+; RUN: ld.lld --plugin-opt=thinlto-index-only -shared %t1.bc %t2.bc
+; RUN: clang -O3 -fthinlto-index=%t1.bc.thinlto.bc -x ir %t1.bc -S -emit-llvm -o - | FileCheck %s
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+$_Z5func1v = comdat any
+
+define linkonce_odr dso_local void @_Z5func1v() unnamed_addr !dbg !10 {
+  ret void
+}
+
+; Dummy function to use _Z5func1v so that it is not treated as dead symbol.
+define void @_Z3bazv() {
+  tail call void @_Z5func1v()
+  ret void
+}
+
+declare void @_Z8thinlto1v() unnamed_addr
+
+; CHECK: void @_Z3barv()
+; CHECK-NOT: call void @_Z8thinlto1v()
+; CHECK-NEXT: ret void
+define void @_Z3barv() unnamed_addr !dbg !14 {
+  tail call void @_Z8thinlto1v(), !dbg !25
+  ret void
+}
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!2, !3, !4, !5}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus_14, file: !1, producer: "clang", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug, splitDebugInlining: false, nameTableKind: None)
+!1 = !DIFile(filename: "A.cpp", directory: ".")
+!2 = !{i32 7, !"Dwarf Version", i32 4}
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = !{i32 1, !"wchar_size", i32 4}
+!5 = !{i32 8, !"PIC Level", i32 2}
+!10 = distinct !DISubprogram(name: "func1", linkageName: "_Z5func1v", scope: !11, file: !11, line: 6, type: !12, scopeLine: 6, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0)
+!11 = !DIFile(filename: "a.h", directory: ".")
+!12 = !DISubroutineType(types: !13)
+!13 = !{null}
+!14 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !11, file: !11, line: 15, type: !12, scopeLine: 15, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !0, retainedNodes: !16)
+!16 = !{!17}
+!17 = !DILocalVariable(name: "s", scope: !14, file: !11, line: 10, type: !18)
+!18 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S<&func1>", file: !11, line: 2, size: 8, flags: DIFlagTypePassByValue, elements: !19, templateParams: !20, identifier: "_ZTS1SIXadL_Z5func1vEEE")
+!19 = !{}
+!20 = !{!21}
+!21 = !DITemplateValueParameter(name: "Func", type: !22, value: ptr @_Z5func1v)
+!22 = !DIDerivedType(tag: DW_TAG_pointer_type, baseType: !12, size: 64)
+!25 = !DILocation(line: 16, column: 5, scope: !14)