Fixed Dwarf debug info emission to skip DILexicalBlockFile entries

[aaboud]

Summary

Without this change the imported entity defined under DILexicalBlockFile (in the test example) will be created under DW_TAG_lexical_block corresponded with DILexicalBlockFile.
This will not happen for a local variable.

Notice that I am fine with creating lexical block entry for each DILexicalBlockFile, but either we do so for all local decls or for none.

[aprantl]

Since this is such a common pattern; what about adding a getNonLexicalBlockFileParent() (better names appreciated) to DIScope?

[aprantl]

This would also be a good place for documenting why a consumer would want to skip over DILexicalBlockFiles.

[aaboud]

Followed Adrian comment.
Introduced DILocalScope::getNonLexicalBlockFileScope() function and used it everywhere we look for the real basic block and want to skip the DILexicalBlockFile entries.

[aaboud]

As for names, yeah... be nice if we had a better name for LexicalBlockFile - it's not really a LexicalBlock at all, as such. Though I suppose we still use them as strict nesting, etc. Meh.

David, do you suggest a different name for the function I am adding, or you want to change the name of the DILexicalBlockFile?
How about these suggested names:
getNonFileScope()
getRealScope()
getSourceLocalScope()

Or you prefer other name?

[dblaikie]

Nah, just go with it - if someone figures out a better name some time we
can change it then.

lib/CodeGen/AsmPrinter/DwarfCompileUnit.h

public:
   DIE::value_iterator addSectionDelta(DIE &Die, dwarf::Attribute Attribute,
                                       const MCSymbol *Hi, const MCSymbol *Lo);
 
   DwarfCompileUnit &getCU() override { return *this; }
 
   unsigned getOrCreateSourceID(StringRef FileName, StringRef DirName) override;
 
   void addImportedEntity(const DIImportedEntity* IE) {
-    ImportedEntities[IE->getScope()].push_back(IE);
+    DIScope *Scope = IE->getScope();
+    while (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
+      Scope = File->getScope();
+    ImportedEntities[Scope].push_back(IE);
   }
 
   /// addRange - Add an address range to the list of ranges for this unit.
   void addRange(RangeSpan Range);
 
   void attachLowHighPC(DIE &D, const MCSymbol *Begin, const MCSymbol *End);
 
   /// addSectionLabel - Add a Dwarf section label attribute data and value.

lib/CodeGen/LexicalScopes.cpp

 /// given DebugLoc. Return NULL if not found.
 LexicalScope *LexicalScopes::findLexicalScope(const DILocation *DL) {
   DILocalScope *Scope = DL->getScope();
   if (!Scope)
     return nullptr;
 
   // The scope that we were created with could have an extra file - which
   // isn't what we care about in this case.
-  if (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
+  while (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
     Scope = File->getScope();
 
   if (auto *IA = DL->getInlinedAt()) {
     auto I = InlinedLexicalScopeMap.find(std::make_pair(Scope, IA));
     return I != InlinedLexicalScopeMap.end() ? &I->second : nullptr;
   }
   return findLexicalScope(Scope);
 }
LexicalScope *LexicalScopes::getOrCreateLexicalScope(const DILocalScope *Scope,
   }
 
   return getOrCreateRegularScope(Scope);
 }
 
 /// getOrCreateRegularScope - Find or create a regular lexical scope.
 LexicalScope *
 LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
-  if (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
+  while (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
     Scope = File->getScope();
 
   auto I = LexicalScopeMap.find(Scope);
   if (I != LexicalScopeMap.end())
     return &I->second;
 
   // FIXME: Should the following dyn_cast be DILexicalBlock?
   LexicalScope *Parent = nullptr;
LexicalScopes::getOrCreateRegularScope(const DILocalScope *Scope) {
 
   return &I->second;
 }
 
 /// getOrCreateInlinedScope - Find or create an inlined lexical scope.
 LexicalScope *
 LexicalScopes::getOrCreateInlinedScope(const DILocalScope *Scope,
                                        const DILocation *InlinedAt) {
+  while (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
+    Scope = File->getScope();
   std::pair<const DILocalScope *, const DILocation *> P(Scope, InlinedAt);
   auto I = InlinedLexicalScopeMap.find(P);
   if (I != InlinedLexicalScopeMap.end())
     return &I->second;
 
   LexicalScope *Parent;
   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))
     Parent = getOrCreateInlinedScope(Block->getScope(), InlinedAt);
   else
     Parent = getOrCreateLexicalScope(InlinedAt);
 
   I = InlinedLexicalScopeMap.emplace(std::piecewise_construct,
                                      std::forward_as_tuple(P),
                                      std::forward_as_tuple(Parent, Scope,
                                                            InlinedAt, false))
           .first;
   return &I->second;
 }
 
 /// getOrCreateAbstractScope - Find or create an abstract lexical scope.
 LexicalScope *
 LexicalScopes::getOrCreateAbstractScope(const DILocalScope *Scope) {
   assert(Scope && "Invalid Scope encoding!");
 
-  if (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
+  while (auto *File = dyn_cast<DILexicalBlockFile>(Scope))
     Scope = File->getScope();
   auto I = AbstractScopeMap.find(Scope);
   if (I != AbstractScopeMap.end())
     return &I->second;
 
   // FIXME: Should the following isa be DILexicalBlock?
   LexicalScope *Parent = nullptr;
   if (auto *Block = dyn_cast<DILexicalBlockBase>(Scope))

test/DebugInfo/X86/lexical-block-file-inline.ll

+; RUN: llc -mtriple=x86_64-unknown-linux-gnu -filetype=obj -O0 < %s  | llvm-dwarfdump -debug-dump=info - | FileCheck %s
+
+;; This test checks that Inlined DILexicalBlockFile with local decl entry
+;; is skipped and only one DW_TAG_lexical_block is generated.
+;; This test is special because it contains DILexicalBlockFile that has a
+;; DILexicalBlockFile as a parent scope.
+;;
+;; This test was generated by running following command:
+;; clang -cc1 -O0 -debug-info-kind=limited -dwarf-version=4 -emit-llvm test.cpp
+;; Where test.cpp
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+;;namespace N {}
+;; __attribute__((always_inline)) int bar() {
+;;  {
+;;    int y;
+;;#line 1 "test.h"
+;;    using namespace N;
+;;    while (y < 0) return 2;
+;;    return 0;
+;;  }
+;;}
+;;int foo() {  
+;;  return bar();
+;;}
+;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
+
+;; Concrete "bar" function
+; CHECK:    DW_TAG_subprogram
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_AT_abstract_origin {{.*}} {[[Offset_bar:0x[0-9abcdef]+]]}
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_TAG_lexical_block
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:        DW_TAG_variable
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:        DW_TAG_imported_module
+
+;; Abstract "bar" function
+; CHECK:    [[Offset_bar]]: DW_TAG_subprogram
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_AT_name {{.*}} "bar"
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_AT_inline
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_TAG_lexical_block
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:        DW_TAG_variable
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:        DW_TAG_imported_module
+
+; CHECK:    DW_TAG_subprogram
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:      DW_AT_name {{.*}} "foo"
+; CHECK-NOT: {{NULL}}
+
+;; Inlined "bar" function
+; CHECK:      DW_TAG_inlined_subroutine
+; CHECK-NEXT:   DW_AT_abstract_origin {{.*}} {[[Offset_bar]]}
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:        DW_TAG_lexical_block
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:          DW_TAG_variable
+; CHECK-NOT: {{DW_TAG|NULL}}
+; CHECK:          DW_TAG_imported_module
+
+
+; Function Attrs: alwaysinline nounwind
+define i32 @_Z3barv() #0 !dbg !4 {
+entry:
+  %retval = alloca i32, align 4
+  %y = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %y, metadata !18, metadata !19), !dbg !20
+  br label %while.cond, !dbg !21
+
+while.cond:                                       ; preds = %entry
+  %0 = load i32, i32* %y, align 4, !dbg !22
+  %cmp = icmp slt i32 %0, 0, !dbg !22
+  br i1 %cmp, label %while.body, label %while.end, !dbg !22
+
+while.body:                                       ; preds = %while.cond
+  store i32 2, i32* %retval, align 4, !dbg !24
+  br label %return, !dbg !24
+
+while.end:                                        ; preds = %while.cond
+  store i32 0, i32* %retval, align 4, !dbg !26
+  br label %return, !dbg !26
+
+return:                                           ; preds = %while.end, %while.body
+  %1 = load i32, i32* %retval, align 4, !dbg !27
+  ret i32 %1, !dbg !27
+}
+
+; Function Attrs: nounwind readnone
+declare void @llvm.dbg.declare(metadata, metadata, metadata) #1
+
+; Function Attrs: nounwind
+define i32 @_Z3foov() #2 !dbg !8 {
+entry:
+  %retval.i = alloca i32, align 4
+  %y.i = alloca i32, align 4
+  call void @llvm.dbg.declare(metadata i32* %y.i, metadata !18, metadata !19), !dbg !29
+  %0 = load i32, i32* %y.i, align 4, !dbg !31
+  %cmp.i = icmp slt i32 %0, 0, !dbg !31
+  br i1 %cmp.i, label %while.body.i, label %while.end.i, !dbg !31
+
+while.body.i:                                     ; preds = %entry
+  store i32 2, i32* %retval.i, align 4, !dbg !32
+  br label %_Z3barv.exit, !dbg !32
+
+while.end.i:                                      ; preds = %entry
+  store i32 0, i32* %retval.i, align 4, !dbg !33
+  br label %_Z3barv.exit, !dbg !33
+
+_Z3barv.exit:                                     ; preds = %while.end.i, %while.body.i
+  %1 = load i32, i32* %retval.i, align 4, !dbg !34
+  ret i32 %1, !dbg !35
+}
+
+attributes #0 = { alwaysinline nounwind }
+attributes #1 = { nounwind readnone }
+attributes #2 = { nounwind }
+
+!llvm.dbg.cu = !{!0}
+!llvm.module.flags = !{!15, !16}
+!llvm.ident = !{!17}
+
+!0 = distinct !DICompileUnit(language: DW_LANG_C_plus_plus, file: !1, producer: "clang version 3.9.0 (trunk 264349)", isOptimized: false, runtimeVersion: 0, emissionKind: 1, enums: !2, subprograms: !3, imports: !10)
+!1 = !DIFile(filename: "test.cpp", directory: "/")
+!2 = !{}
+!3 = !{!4, !8}
+!4 = distinct !DISubprogram(name: "bar", linkageName: "_Z3barv", scope: !1, file: !1, line: 2, type: !5, isLocal: false, isDefinition: true, scopeLine: 2, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!5 = !DISubroutineType(types: !6)
+!6 = !{!7}
+!7 = !DIBasicType(name: "int", size: 32, align: 32, encoding: DW_ATE_signed)
+!8 = distinct !DISubprogram(name: "foo", linkageName: "_Z3foov", scope: !9, file: !9, line: 6, type: !5, isLocal: false, isDefinition: true, scopeLine: 6, flags: DIFlagPrototyped, isOptimized: false, variables: !2)
+!9 = !DIFile(filename: "test.h", directory: "/")
+!10 = !{!11}
+!11 = !DIImportedEntity(tag: DW_TAG_imported_module, scope: !12, entity: !14, line: 1)
+!12 = !DILexicalBlockFile(scope: !13, file: !9, discriminator: 0)
+!13 = distinct !DILexicalBlock(scope: !4, file: !1, line: 3)
+!14 = !DINamespace(name: "N", scope: null, file: !1, line: 1)
+!15 = !{i32 2, !"Dwarf Version", i32 4}
+!16 = !{i32 2, !"Debug Info Version", i32 3}
+!17 = !{!"clang version 3.9.0 (trunk 264349)"}
+!18 = !DILocalVariable(name: "y", scope: !13, file: !1, line: 4, type: !7)
+!19 = !DIExpression()
+!20 = !DILocation(line: 4, scope: !13)
+!21 = !DILocation(line: 2, scope: !12)
+!22 = !DILocation(line: 2, scope: !23)
+!23 = !DILexicalBlockFile(scope: !12, file: !9, discriminator: 1)
+!24 = !DILocation(line: 2, scope: !25)
+!25 = !DILexicalBlockFile(scope: !12, file: !9, discriminator: 2)
+!26 = !DILocation(line: 3, scope: !12)
+!27 = !DILocation(line: 5, scope: !28)
+!28 = !DILexicalBlockFile(scope: !4, file: !9, discriminator: 0)
+!29 = !DILocation(line: 4, scope: !13, inlinedAt: !30)
+!30 = distinct !DILocation(line: 7, scope: !8)
+!31 = !DILocation(line: 2, scope: !23, inlinedAt: !30)
+!32 = !DILocation(line: 2, scope: !25, inlinedAt: !30)
+!33 = !DILocation(line: 3, scope: !12, inlinedAt: !30)
+!34 = !DILocation(line: 5, scope: !28, inlinedAt: !30)
+!35 = !DILocation(line: 7, scope: !8)