[Lldb-commits] [lldb] [lldb][DWARF] Delay struct/class/union definition DIE searching when parsing declaration DIEs. (PR #90663)
via lldb-commits
lldb-commits at lists.llvm.org
Tue Apr 30 13:57:05 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-lldb
Author: Zequan Wu (ZequanWu)
<details>
<summary>Changes</summary>
This is the implementation for https://discourse.llvm.org/t/rfc-delay-definition-die-searching-when-parse-a-declaration-die-for-record-type/78526.
#### Motivation
Currently, lldb eagerly searches for definition DIE when parsing a declaration DIE for struct/class/union definition DIE. It will search for all definition DIEs with the same unqualified name (just `DW_AT_name` ) and then find out those DIEs with same fully qualified name. Then lldb will try to resolve those DIEs to create the Types from definition DIEs. It works fine most time. However, when built with `-gsimple-template-names`, the search graph expands very quickly, because for the specialized-template classes, they don’t have template parameter names encoded inside `DW_AT_name`. They have `DW_TAG_template_type_parameter` to reference the types used as template parameters. In order to identify if a definition DIE matches a declaration DIE, lldb needs to resolve all template parameter types first and those template parameter types might be template classes as well, and so on… So, the search graph explodes, causing a lot unnecessary searching/type-resolving to just get the fully qualified names for a specialized-template class. This causes lldb stack overflow for us internally on template-heavy libraries.
#### Implementation
Instead of searching for definition DIEs when parsing declaration DIEs, we always construct the record type from the DIE regardless if it's definition or declaration. At the same time, use a map `GetDeclarationDIEToDefinitionDIE()` to track the mapping from declarations/definition DIEs to the unique definition DIE. The process of searching for definition DIE is refactored to `SymbolFileDWARF::FindDefinitionDIE` which is invoked when 1) completing the type on `SymbolFileDWARF::CompleteType`. 2) the record type needs to start its definition as a containing type so that nested classes can be added into it in `PrepareContextToReceiveMembers`.
The key difference is `SymbolFileDWARF::ResolveType` return a `Type*` that might be created from declaration DIE, which means it hasn't starts its definition yet. We also need to change according in places where we want the type to start definition, like `PrepareContextToReceiveMembers` (I'm not aware of any other places, but this should be a simple call to `SymbolFileDWARF::FindDefinitionDIE`)
#### Result
It fixes the stack overflow of lldb for the internal binary built with simple template name. When constructing the fully qualified name built with `-gsimple-template-names`, it gets the name of the type parameter by resolving the referenced DIE, which might be a declaration (we won't try to search for the definition DIE to just get the name).
---
Patch is 34.35 KiB, truncated to 20.00 KiB below, full version: https://github.com/llvm/llvm-project/pull/90663.diff
7 Files Affected:
- (modified) lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp (+107-163)
- (modified) lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp (+103-2)
- (modified) lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.h (+14)
- (modified) lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.cpp (+5)
- (modified) lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARFDwo.h (+2)
- (modified) lldb/source/Plugins/SymbolFile/DWARF/UniqueDWARFASTType.cpp (+50-45)
- (modified) lldb/source/Plugins/SymbolFile/DWARF/UniqueDWARFASTType.h (+15-6)
``````````diff
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
index bea11e0e3840af..7ad661c9a9d49b 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
@@ -252,7 +252,8 @@ static void ForcefullyCompleteType(CompilerType type) {
static void PrepareContextToReceiveMembers(TypeSystemClang &ast,
ClangASTImporter &ast_importer,
clang::DeclContext *decl_ctx,
- DWARFDIE die,
+ const DWARFDIE &decl_ctx_die,
+ const DWARFDIE &die,
const char *type_name_cstr) {
auto *tag_decl_ctx = clang::dyn_cast<clang::TagDecl>(decl_ctx);
if (!tag_decl_ctx)
@@ -279,6 +280,13 @@ static void PrepareContextToReceiveMembers(TypeSystemClang &ast,
type_name_cstr ? type_name_cstr : "", die.GetOffset());
}
+ // By searching for the definition DIE of the decl_ctx type, we will either:
+ // 1. Found the the definition DIE and start its definition with
+ // TypeSystemClang::StartTagDeclarationDefinition.
+ // 2. Unable to find it, then need to forcefully complete it.
+ die.GetDWARF()->FindDefinitionDIE(decl_ctx_die);
+ if (tag_decl_ctx->isCompleteDefinition() || tag_decl_ctx->isBeingDefined())
+ return;
// We don't have a type definition and/or the import failed. We must
// forcefully complete the type to avoid crashes.
ForcefullyCompleteType(type);
@@ -620,10 +628,11 @@ DWARFASTParserClang::ParseTypeModifier(const SymbolContext &sc,
if (tag == DW_TAG_typedef) {
// DeclContext will be populated when the clang type is materialized in
// Type::ResolveCompilerType.
- PrepareContextToReceiveMembers(
- m_ast, GetClangASTImporter(),
- GetClangDeclContextContainingDIE(die, nullptr), die,
- attrs.name.GetCString());
+ DWARFDIE decl_ctx_die;
+ clang::DeclContext *decl_ctx =
+ GetClangDeclContextContainingDIE(die, &decl_ctx_die);
+ PrepareContextToReceiveMembers(m_ast, GetClangASTImporter(), decl_ctx,
+ decl_ctx_die, die, attrs.name.GetCString());
if (attrs.type.IsValid()) {
// Try to parse a typedef from the (DWARF embedded in the) Clang
@@ -1100,32 +1109,6 @@ DWARFASTParserClang::ParseSubroutine(const DWARFDIE &die,
// struct and see if this is actually a C++ method
Type *class_type = dwarf->ResolveType(decl_ctx_die);
if (class_type) {
- if (class_type->GetID() != decl_ctx_die.GetID() ||
- IsClangModuleFwdDecl(decl_ctx_die)) {
-
- // We uniqued the parent class of this function to another
- // class so we now need to associate all dies under
- // "decl_ctx_die" to DIEs in the DIE for "class_type"...
- DWARFDIE class_type_die = dwarf->GetDIE(class_type->GetID());
-
- if (class_type_die) {
- std::vector<DWARFDIE> failures;
-
- CopyUniqueClassMethodTypes(decl_ctx_die, class_type_die,
- class_type, failures);
-
- // FIXME do something with these failures that's
- // smarter than just dropping them on the ground.
- // Unfortunately classes don't like having stuff added
- // to them after their definitions are complete...
-
- Type *type_ptr = dwarf->GetDIEToType()[die.GetDIE()];
- if (type_ptr && type_ptr != DIE_IS_BEING_PARSED) {
- return type_ptr->shared_from_this();
- }
- }
- }
-
if (attrs.specification.IsValid()) {
// We have a specification which we are going to base our
// function prototype off of, so we need this type to be
@@ -1260,6 +1243,39 @@ DWARFASTParserClang::ParseSubroutine(const DWARFDIE &die,
}
}
}
+ // By here, we should have already completed the c++ class_type
+ // because if either specification or abstract_origin is present, we
+ // call GetClangDeclContextForDIE to resolve the DW_TAG_subprogram
+ // refered by this one until we reached the DW_TAG_subprogram without
+ // specification or abstract_origin (the else branch above). Then the
+ // above GetFullCompilerType() will complete the class_type if it's
+ // not completed yet. After that, we will have the mapping from DIEs
+ // in class_type_die to DeclContexts in m_die_to_decl_ctx.
+ if (class_type->GetID() != decl_ctx_die.GetID() ||
+ IsClangModuleFwdDecl(decl_ctx_die)) {
+
+ // We uniqued the parent class of this function to another
+ // class so we now need to associate all dies under
+ // "decl_ctx_die" to DIEs in the DIE for "class_type"...
+ DWARFDIE class_type_die = dwarf->GetDIE(class_type->GetID());
+
+ if (class_type_die) {
+ std::vector<DWARFDIE> failures;
+
+ CopyUniqueClassMethodTypes(decl_ctx_die, class_type_die,
+ class_type, failures);
+
+ // FIXME do something with these failures that's
+ // smarter than just dropping them on the ground.
+ // Unfortunately classes don't like having stuff added
+ // to them after their definitions are complete...
+
+ Type *type_ptr = dwarf->GetDIEToType()[die.GetDIE()];
+ if (type_ptr && type_ptr != DIE_IS_BEING_PARSED) {
+ return type_ptr->shared_from_this();
+ }
+ }
+ }
}
}
}
@@ -1651,6 +1667,7 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
ConstString unique_typename(attrs.name);
Declaration unique_decl(attrs.decl);
+ uint64_t byte_size = attrs.byte_size.value_or(0);
if (attrs.name) {
if (Language::LanguageIsCPlusPlus(cu_language)) {
@@ -1664,13 +1681,34 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
}
if (dwarf->GetUniqueDWARFASTTypeMap().Find(
- unique_typename, die, unique_decl, attrs.byte_size.value_or(-1),
- *unique_ast_entry_up)) {
+ unique_typename, die, unique_decl, byte_size,
+ attrs.is_forward_declaration, *unique_ast_entry_up)) {
type_sp = unique_ast_entry_up->m_type_sp;
if (type_sp) {
dwarf->GetDIEToType()[die.GetDIE()] = type_sp.get();
LinkDeclContextToDIE(
GetCachedClangDeclContextForDIE(unique_ast_entry_up->m_die), die);
+ if (!attrs.is_forward_declaration) {
+ dwarf->GetDeclarationDIEToDefinitionDIE().try_emplace(
+ unique_ast_entry_up->m_die.GetDIE(), *die.GetDIERef());
+ // If the parameter DIE is definition and the entry in the map is
+ // declaration, then we need to update the entry to point to the
+ // definition DIE.
+ if (unique_ast_entry_up->m_is_forward_declaration) {
+ unique_ast_entry_up->m_die = die;
+ unique_ast_entry_up->m_byte_size = byte_size;
+ unique_ast_entry_up->m_declaration = unique_decl;
+ unique_ast_entry_up->m_is_forward_declaration = false;
+ // Need to update Type ID to refer to the definition DIE. because
+ // it's used in ParseSubroutine to determine if we need to copy cxx
+ // method types from a declaration DIE to this definition DIE.
+ type_sp->SetID(die.GetID());
+ if (attrs.class_language != eLanguageTypeObjC &&
+ attrs.class_language != eLanguageTypeObjC_plus_plus)
+ TypeSystemClang::StartTagDeclarationDefinition(
+ type_sp->GetForwardCompilerType());
+ }
+ }
return type_sp;
}
}
@@ -1707,112 +1745,22 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
attrs.is_forward_declaration = true;
}
- if (attrs.class_language == eLanguageTypeObjC ||
- attrs.class_language == eLanguageTypeObjC_plus_plus) {
- if (!attrs.is_complete_objc_class &&
- die.Supports_DW_AT_APPLE_objc_complete_type()) {
- // We have a valid eSymbolTypeObjCClass class symbol whose name
- // matches the current objective C class that we are trying to find
- // and this DIE isn't the complete definition (we checked
- // is_complete_objc_class above and know it is false), so the real
- // definition is in here somewhere
- type_sp =
- dwarf->FindCompleteObjCDefinitionTypeForDIE(die, attrs.name, true);
-
- if (!type_sp) {
- SymbolFileDWARFDebugMap *debug_map_symfile =
- dwarf->GetDebugMapSymfile();
- if (debug_map_symfile) {
- // We weren't able to find a full declaration in this DWARF,
- // see if we have a declaration anywhere else...
- type_sp = debug_map_symfile->FindCompleteObjCDefinitionTypeForDIE(
- die, attrs.name, true);
- }
- }
-
- if (type_sp) {
- if (log) {
- dwarf->GetObjectFile()->GetModule()->LogMessage(
- log,
- "SymbolFileDWARF({0:p}) - {1:x16}: {2} type "
- "\"{3}\" is an "
- "incomplete objc type, complete type is {4:x8}",
- static_cast<void *>(this), die.GetOffset(),
- DW_TAG_value_to_name(tag), attrs.name.GetCString(),
- type_sp->GetID());
- }
-
- // We found a real definition for this type elsewhere so lets use
- // it and cache the fact that we found a complete type for this
- // die
- dwarf->GetDIEToType()[die.GetDIE()] = type_sp.get();
- return type_sp;
- }
- }
- }
-
if (attrs.is_forward_declaration) {
- // We have a forward declaration to a type and we need to try and
- // find a full declaration. We look in the current type index just in
- // case we have a forward declaration followed by an actual
- // declarations in the DWARF. If this fails, we need to look
- // elsewhere...
- if (log) {
- dwarf->GetObjectFile()->GetModule()->LogMessage(
- log,
- "SymbolFileDWARF({0:p}) - {1:x16}: {2} type \"{3}\" is a "
- "forward declaration, trying to find complete type",
- static_cast<void *>(this), die.GetOffset(), DW_TAG_value_to_name(tag),
- attrs.name.GetCString());
- }
-
// See if the type comes from a Clang module and if so, track down
// that type.
type_sp = ParseTypeFromClangModule(sc, die, log);
if (type_sp)
return type_sp;
-
- // type_sp = FindDefinitionTypeForDIE (dwarf_cu, die,
- // type_name_const_str);
- type_sp = dwarf->FindDefinitionTypeForDWARFDeclContext(die);
-
- if (!type_sp) {
- SymbolFileDWARFDebugMap *debug_map_symfile = dwarf->GetDebugMapSymfile();
- if (debug_map_symfile) {
- // We weren't able to find a full declaration in this DWARF, see
- // if we have a declaration anywhere else...
- type_sp = debug_map_symfile->FindDefinitionTypeForDWARFDeclContext(die);
- }
- }
-
- if (type_sp) {
- if (log) {
- dwarf->GetObjectFile()->GetModule()->LogMessage(
- log,
- "SymbolFileDWARF({0:p}) - {1:x16}: {2} type \"{3}\" is a "
- "forward declaration, complete type is {4:x8}",
- static_cast<void *>(this), die.GetOffset(),
- DW_TAG_value_to_name(tag), attrs.name.GetCString(),
- type_sp->GetID());
- }
-
- // We found a real definition for this type elsewhere so lets use
- // it and cache the fact that we found a complete type for this die
- dwarf->GetDIEToType()[die.GetDIE()] = type_sp.get();
- clang::DeclContext *defn_decl_ctx =
- GetCachedClangDeclContextForDIE(dwarf->GetDIE(type_sp->GetID()));
- if (defn_decl_ctx)
- LinkDeclContextToDIE(defn_decl_ctx, die);
- return type_sp;
- }
}
+
assert(tag_decl_kind != -1);
UNUSED_IF_ASSERT_DISABLED(tag_decl_kind);
- bool clang_type_was_created = false;
- clang::DeclContext *decl_ctx = GetClangDeclContextContainingDIE(die, nullptr);
+ DWARFDIE decl_ctx_die;
+ clang::DeclContext *decl_ctx =
+ GetClangDeclContextContainingDIE(die, &decl_ctx_die);
- PrepareContextToReceiveMembers(m_ast, GetClangASTImporter(), decl_ctx, die,
- attrs.name.GetCString());
+ PrepareContextToReceiveMembers(m_ast, GetClangASTImporter(), decl_ctx,
+ decl_ctx_die, die, attrs.name.GetCString());
if (attrs.accessibility == eAccessNone && decl_ctx) {
// Check the decl context that contains this class/struct/union. If
@@ -1850,20 +1798,20 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
tag_decl_kind, template_param_infos);
clang_type =
m_ast.CreateClassTemplateSpecializationType(class_specialization_decl);
- clang_type_was_created = true;
m_ast.SetMetadata(class_template_decl, metadata);
m_ast.SetMetadata(class_specialization_decl, metadata);
}
- if (!clang_type_was_created) {
- clang_type_was_created = true;
+ if (!clang_type) {
clang_type = m_ast.CreateRecordType(
decl_ctx, GetOwningClangModule(die), attrs.accessibility,
attrs.name.GetCString(), tag_decl_kind, attrs.class_language, &metadata,
attrs.exports_symbols);
}
-
+ if (!attrs.is_forward_declaration)
+ dwarf->GetDeclarationDIEToDefinitionDIE().try_emplace(die.GetDIE(),
+ *die.GetDIERef());
// Store a forward declaration to this class type in case any
// parameters in any class methods need it for the clang types for
// function prototypes.
@@ -1880,7 +1828,8 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
unique_ast_entry_up->m_type_sp = type_sp;
unique_ast_entry_up->m_die = die;
unique_ast_entry_up->m_declaration = unique_decl;
- unique_ast_entry_up->m_byte_size = attrs.byte_size.value_or(0);
+ unique_ast_entry_up->m_byte_size = byte_size;
+ unique_ast_entry_up->m_is_forward_declaration = attrs.is_forward_declaration;
dwarf->GetUniqueDWARFASTTypeMap().Insert(unique_typename,
*unique_ast_entry_up);
@@ -1921,38 +1870,33 @@ DWARFASTParserClang::ParseStructureLikeDIE(const SymbolContext &sc,
GetClangASTImporter().SetRecordLayout(record_decl, layout);
}
}
- } else if (clang_type_was_created) {
- // Start the definition if the class is not objective C since the
- // underlying decls respond to isCompleteDefinition(). Objective
- // C decls don't respond to isCompleteDefinition() so we can't
- // start the declaration definition right away. For C++
- // class/union/structs we want to start the definition in case the
- // class is needed as the declaration context for a contained class
- // or type without the need to complete that type..
-
- if (attrs.class_language != eLanguageTypeObjC &&
- attrs.class_language != eLanguageTypeObjC_plus_plus)
- TypeSystemClang::StartTagDeclarationDefinition(clang_type);
-
- // Leave this as a forward declaration until we need to know the
- // details of the type. lldb_private::Type will automatically call
- // the SymbolFile virtual function
- // "SymbolFileDWARF::CompleteType(Type *)" When the definition
- // needs to be defined.
- assert(!dwarf->GetForwardDeclCompilerTypeToDIE().count(
- ClangUtil::RemoveFastQualifiers(clang_type)
- .GetOpaqueQualType()) &&
- "Type already in the forward declaration map!");
- // Can't assume m_ast.GetSymbolFile() is actually a
- // SymbolFileDWARF, it can be a SymbolFileDWARFDebugMap for Apple
- // binaries.
- dwarf->GetForwardDeclCompilerTypeToDIE().try_emplace(
- ClangUtil::RemoveFastQualifiers(clang_type).GetOpaqueQualType(),
- *die.GetDIERef());
- m_ast.SetHasExternalStorage(clang_type.GetOpaqueQualType(), true);
}
+ // Start the definition if the class is not objective C since the
+ // underlying decls respond to isCompleteDefinition(). Objective
+ // C decls don't respond to isCompleteDefinition() so we can't
+ // start the declaration definition right away. For C++
+ // class/union/structs we want to start the definition in case the
+ // class is needed as the declaration context for a contained class
+ // or type without the need to complete that type..
+
+ if (attrs.class_language != eLanguageTypeObjC &&
+ attrs.class_language != eLanguageTypeObjC_plus_plus)
+ TypeSystemClang::StartTagDeclarationDefinition(clang_type);
}
+ // Leave this as a forward declaration until we need to know the
+ // details of the type. lldb_private::Type will automatically call
+ // the SymbolFile virtual function
+ // "SymbolFileDWARF::CompleteType(Type *)" When the definition
+ // needs to be defined.
+ assert(!dwarf->GetForwardDeclCompilerTypeToDIE().count(
+ ClangUtil::RemoveFastQualifiers(clang_type).GetOpaqueQualType()) &&
+ "Type already in the forward declaration map!");
+ dwarf->GetForwardDeclCompilerTypeToDIE().try_emplace(
+ ClangUtil::RemoveFastQualifiers(clang_type).GetOpaqueQualType(),
+ *die.GetDIERef());
+ m_ast.SetHasExternalStorage(clang_type.GetOpaqueQualType(), true);
+
// If we made a clang type, set the trivial abi if applicable: We only
// do this for pass by value - which implies the Trivial ABI. There
// isn't a way to assert that something that would normally be pass by
diff --git a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
index 49f13d2c89e380..5a317db7e74028 100644
--- a/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
+++ b/lldb/source/Plugins/SymbolFile/DWARF/SymbolFileDWARF.cpp
@@ -1631,13 +1631,19 @@ bool SymbolFileDWARF::CompleteType(CompilerType &compiler_type) {
return true;
}
- DWARFDIE dwarf_die = GetDIE(die_it->getSecond());
+ DWARFDIE dwarf_die = FindDefinitionDIE(GetDIE(die_it->getSecond()));
if (dwarf_die) {
// Once we start resolving this type, remove it from the forward
// declaration map in case anyone child members or other types require this
// type to get resolved. The type will get resolved when all of the calls
// to SymbolFileDWARF::ResolveClangOpaqueTypeDefinition are done.
- GetForwardDeclCompilerTypeToDIE().erase(die_it);
+ // Need to get a new iterator because FindDefinitionDIE might add new
+ // entries into the map and invalidate previous iterator.
+ auto die_it = GetForwardDeclCompilerTypeToDIE().find(
+ compiler_type_no_qualifiers.GetOpaqueQualType());
+ if (die_it != GetForwardDeclCompilerTypeToDIE().end()) {
+ GetForwardDeclCompilerTypeToDIE().erase(die_it);
+ }
Type *type = GetDIEToType().lookup(dwarf_die.GetDIE());
@@ -1654,6 +1660,101 @@ bool SymbolFileDWARF::CompleteType(CompilerType &compiler_type) {
return false;
}
+DWARFDIE SymbolFileDWARF::FindDefinitionDIE(const DWARFDIE &die) {
+ auto def_die_it = GetDeclarationDIEToDefinitionDIE().find(die.GetDIE());
+ if (def_die_it != GetDeclarationDIEToDefinitionDIE().end())
+ return GetDIE(def_die_it->getSecond());
+
+ ParsedDWARFTypeAttributes attrs(die);
+ const dw_tag_t tag = die.Tag();
+ TypeSP type_sp;
+ Log *log = GetLog(DWARFLog::TypeCompletion | DWARFLog::Lookups);
+ if (log) {
+ GetObjectFile()->GetModule()->LogMessage(
+ log,
+ "SymbolFileDWARF({0:p}) - {1:x16}: {2} type \"{3}\" is a "
+ "forward declaration DIE, trying to find definition DIE",
+ static_cast<void *>(this), die.GetOffset(), DW_TAG_value_to_name(tag),
+ attrs.name.GetCString());
+ }
+ // We haven't parse definition die for this type, starting to search for it.
+ // After we found the definition die, the GetDeclarationDIEToDefinitionDIE()...
[truncated]
``````````
</details>
https://github.com/llvm/llvm-project/pull/90663
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