[DebugInfo] Fix potential CU mismatch for SubprogramScopeDIEs.

In constructAbstractSubprogramScopeDIE there can be a potential mismatch
between `this` and the CU of ContextDIE when a scope is shared between
two DISubprograms belonging to a different CU. In that case, `this` is
the CU that was specified in the IR, but the CU of ContextDIE is that of
the first subprogram that was emitted. This patch fixes the mismatch by
looking up the CU of ContextDIE, and switching to use that.

This fixes PR35212 (https://bugs.llvm.org/show_bug.cgi?id=35212)

Patch by Philip Craig!

Differential revision: https://reviews.llvm.org/D39981

llvm-svn: 318289

llvm/lib/CodeGen/AsmPrinter/DwarfCompileUnit.cpp

@@ -638,6 +638,7 @@ void DwarfCompileUnit::constructAbstractSubprogramScopeDIE(
   auto *SP = cast<DISubprogram>(Scope->getScopeNode());
 
   DIE *ContextDIE;
+  DwarfCompileUnit *ContextCU = this;
 
   if (includeMinimalInlineScopes())
     ContextDIE = &getUnitDie();
@@ -648,18 +649,23 @@ void DwarfCompileUnit::constructAbstractSubprogramScopeDIE(
   else if (auto *SPDecl = SP->getDeclaration()) {
     ContextDIE = &getUnitDie();
     getOrCreateSubprogramDIE(SPDecl);
-  } else
+  } else {
     ContextDIE = getOrCreateContextDIE(resolve(SP->getScope()));
+    // The scope may be shared with a subprogram that has already been
+    // constructed in another CU, in which case we need to construct this
+    // subprogram in the same CU.
+    ContextCU = DD->lookupCU(ContextDIE->getUnitDie());
+  }
 
   // Passing null as the associated node because the abstract definition
   // shouldn't be found by lookup.
-  AbsDef = &createAndAddDIE(dwarf::DW_TAG_subprogram, *ContextDIE, nullptr);
-  applySubprogramAttributesToDefinition(SP, *AbsDef);
+  AbsDef = &ContextCU->createAndAddDIE(dwarf::DW_TAG_subprogram, *ContextDIE, nullptr);
+  ContextCU->applySubprogramAttributesToDefinition(SP, *AbsDef);
 
-  if (!includeMinimalInlineScopes())
-    addUInt(*AbsDef, dwarf::DW_AT_inline, None, dwarf::DW_INL_inlined);
-  if (DIE *ObjectPointer = createAndAddScopeChildren(Scope, *AbsDef))
-    addDIEEntry(*AbsDef, dwarf::DW_AT_object_pointer, *ObjectPointer);
+  if (!ContextCU->includeMinimalInlineScopes())
+    ContextCU->addUInt(*AbsDef, dwarf::DW_AT_inline, None, dwarf::DW_INL_inlined);
+  if (DIE *ObjectPointer = ContextCU->createAndAddScopeChildren(Scope, *AbsDef))
+    ContextCU->addDIEEntry(*AbsDef, dwarf::DW_AT_object_pointer, *ObjectPointer);
 }
 
 DIE *DwarfCompileUnit::constructImportedEntityDIE(

llvm/lib/CodeGen/AsmPrinter/DwarfDebug.h

@@ -276,7 +276,7 @@ class DwarfDebug : public DebugHandlerBase {
   // 0, referencing the comp_dir of all the type units that use it.
   MCDwarfDwoLineTable SplitTypeUnitFileTable;
   /// @}
-  
+
   /// True iff there are multiple CUs in this module.
   bool SingleCU;
   bool IsDarwin;
@@ -535,6 +535,9 @@ class DwarfDebug : public DebugHandlerBase {
   /// going to be null.
   bool isLexicalScopeDIENull(LexicalScope *Scope);
 
+  /// Find the matching DwarfCompileUnit for the given CU DIE.
+  DwarfCompileUnit *lookupCU(const DIE *Die) { return CUDieMap.lookup(Die); }
+
   /// \defgroup DebuggerTuning Predicates to tune DWARF for a given debugger.
   ///
   /// Returns whether we are "tuning" for a given debugger.

llvm/test/DebugInfo/cross-cu-scope.ll

@@ -0,0 +1,50 @@
+; RUN: %llc_dwarf %s -filetype=obj -o %t
+; RUN: llvm-dwarfdump -debug-info %t | FileCheck %s
+
+; Reduced test case from PR35212. Two DISubprogram belong to a different CU but
+; share a scope. Both are declarations and end up in the scope's CU. We want to
+; check that the CU from the context DIE is used (rather than from the IR).
+; This manifests itself by the DW_base_type ending up in the second CU, rather
+; than in the first one as specified in the IR.
+
+; CHECK: DW_TAG_compile_unit
+; CHECK-NEXT: discriminator 0
+; CHECK: DW_TAG_compile_unit
+; CHECK-NEXT: discriminator 1
+; CHECK: DW_TAG_structure_type
+; CHECK-NOT: NULL
+; CHECK: DW_TAG_subprogram
+; CHECK-NOT: NULL
+; CHECK: DW_TAG_formal_parameter
+; CHECK-NOT: NULL
+; CHECK: DW_AT_type{{.*}}"usize"
+; CHECK: NULL
+; CHECK: DW_TAG_base_type
+; CHECK-NOT: NULL
+; CHECK: DW_AT_name{{.*}}"usize"
+
+define hidden void @foo() !dbg !4 {
+  ret void, !dbg !7
+}
+
+!llvm.dbg.cu = !{!0, !2}
+!llvm.module.flags = !{!3}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_Rust, file: !1, producer: "clang LLVM (rustc version 1.23.0-nightly (discriminator 0))", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!1 = !DIFile(filename: "../lib.rs", directory: "/home/alex/code/rust4/lol")
+!2 = distinct !DICompileUnit(language: DW_LANG_Rust, file: !1, producer: "clang LLVM (rustc version 1.23.0-nightly (discriminator 1))", isOptimized: true, runtimeVersion: 0, emissionKind: FullDebug)
+!3 = !{i32 2, !"Debug Info Version", i32 3}
+!4 = distinct !DISubprogram(name: "clone<alloc::string::String>", linkageName: "_ZN5alloc3vec8{{impl}}28clone<alloc::string::String>E", scope: null, file: !1, line: 1519, type: !5, isLocal: false, isDefinition: true, scopeLine: 1519, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !6, variables: !6)
+!5 = !DISubroutineType(types: !6)
+!6 = !{}
+!7 = !DILocation(line: 1612, scope: !8, inlinedAt: !11)
+!8 = distinct !DILexicalBlock(scope: !9, file: !1, line: 86, column: 12)
+!9 = distinct !DISubprogram(name: "allocate_in<alloc::string::String,alloc::heap::Heap>", linkageName: "_ZN5alloc7raw_vec8{{impl}}52allocate_in<alloc::string::String,alloc::heap::Heap>E", scope: !10, file: !1, line: 82, type: !5, isLocal: false, isDefinition: true, scopeLine: 82, flags: DIFlagPrototyped, isOptimized: true, unit: !2, templateParams: !6, variables: !6)
+!10 = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "RawVec<alloc::string::String, alloc::heap::Heap>", file: !1, size: 128, align: 64, elements: !6, identifier: "5c6e4db16d2c64555e40661d70c4d81e")
+!11 = distinct !DILocation(line: 86, scope: !8, inlinedAt: !12)
+!12 = distinct !DILocation(line: 141, scope: !13, inlinedAt: !17)
+!13 = distinct !DISubprogram(name: "with_capacity<alloc::string::String>", linkageName: "_ZN5alloc7raw_vec8{{impl}}36with_capacity<alloc::string::String>E", scope: !10, file: !1, line: 140, type: !5, isLocal: false, isDefinition: true, scopeLine: 140, flags: DIFlagPrototyped, isOptimized: true, unit: !0, templateParams: !6, variables: !14)
+!14 = !{!15}
+!15 = !DILocalVariable(name: "cap", arg: 1, scope: !13, file: !1, line: 1, type: !16)
+!16 = !DIBasicType(name: "usize", size: 64, encoding: DW_ATE_unsigned)
+!17 = !DILocation(line: 1521, scope: !4)