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Revert "Reland "clang][DebugInfo] Emit global variable definitions fo…
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…r static data members with constant initializers (#70639)""

This casued asserts:

  llvm/lib/IR/Metadata.cpp:689:
  void llvm::MDNode::resolve(): Assertion `isUniqued() && "Expected this to be uniqued"' failed.

See comments on the PR.

This also reverts the dependent follow-up commits, see below.

> When an LLDB user asks for the value of a static data member, LLDB
> starts by searching the Names accelerator table for the corresponding
> variable definition DIE. For static data members with out-of-class
> definitions that works fine, because those get represented as global
> variables with a location and making them eligible to be added to the
> Names table. However, in-class definitions won<E2><80><99>t get indexed because
> we usually don't emit global variables for them. So in DWARF we end
> up with a single `DW_TAG_member` that usually holds the constant
> initializer.  But we don't get a corresponding CU-level
> `DW_TAG_variable` like we do for out-of-class definitions.
>
> To make it more convenient for debuggers to get to the value of
> inline static data members, this patch makes sure we emit definitions
> for static variables with constant initializers the same way we do
> for other static variables. This also aligns Clang closer to GCC,
> which produces CU-level definitions for inline statics and also
> emits these into `.debug_pubnames`.
>
> The implementation keeps track of newly created static data members.
> Then in `CGDebugInfo::finalize`, we emit a global `DW_TAG_variable`
> with a `DW_AT_const_value` for any of those declarations that didn't
> end up with a definition in the `DeclCache`.
>
> The newly emitted `DW_TAG_variable` will look as follows:
> ```
> 0x0000007b:   DW_TAG_structure_type
>                 DW_AT_calling_convention        (DW_CC_pass_by_value)
>                 DW_AT_name      ("Foo")
>                 ...
>
> 0x0000008d:     DW_TAG_member
>                   DW_AT_name    ("i")
>                   DW_AT_type    (0x00000062 "const int")
>                   DW_AT_external        (true)
>                   DW_AT_declaration     (true)
>                   DW_AT_const_value     (4)
>
> Newly added
> vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv
>
> 0x0000009a:   DW_TAG_variable
>                 DW_AT_specification     (0x0000008d "i")
>                 DW_AT_const_value       (4)
>                 DW_AT_linkage_name      ("_ZN2t2IiE1iIfEE")
> ```
>
> This patch also drops the `DW_AT_const_value` off of the declaration
> since we now always have it on the definition. This ensures that the
> `DWARFParallelLinker` can type-merge class with static members where
> we couldn't attach the constant on the declaration in some CUs.

This reverts commit 7c3707a.
This reverts commit cab0a19.
This reverts commit 317481b.
This reverts commit 15fc809.
This reverts commit 470de2b.
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@zmodem
zmodem committed Nov 7, 2023
1 parent a737a33 commit 066eea7
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Showing 13 changed files with 48 additions and 361 deletions.
58 changes: 11 additions & 47 deletions clang/lib/CodeGen/CGDebugInfo.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1677,13 +1677,22 @@ CGDebugInfo::CreateRecordStaticField(const VarDecl *Var, llvm::DIType *RecordTy,

unsigned LineNumber = getLineNumber(Var->getLocation());
StringRef VName = Var->getName();
llvm::Constant *C = nullptr;
if (Var->getInit()) {
const APValue *Value = Var->evaluateValue();
if (Value) {
if (Value->isInt())
C = llvm::ConstantInt::get(CGM.getLLVMContext(), Value->getInt());
if (Value->isFloat())
C = llvm::ConstantFP::get(CGM.getLLVMContext(), Value->getFloat());
}
}

llvm::DINode::DIFlags Flags = getAccessFlag(Var->getAccess(), RD);
auto Align = getDeclAlignIfRequired(Var, CGM.getContext());
llvm::DIDerivedType *GV = DBuilder.createStaticMemberType(
RecordTy, VName, VUnit, LineNumber, VTy, Flags, /* Val */ nullptr, Align);
RecordTy, VName, VUnit, LineNumber, VTy, Flags, C, Align);
StaticDataMemberCache[Var->getCanonicalDecl()].reset(GV);
StaticDataMemberDefinitionsToEmit.push_back(Var->getCanonicalDecl());
return GV;
}

Expand Down Expand Up @@ -5587,39 +5596,6 @@ void CGDebugInfo::EmitGlobalVariable(const ValueDecl *VD, const APValue &Init) {
TemplateParameters, Align));
}

void CGDebugInfo::EmitGlobalVariable(const VarDecl *VD) {
assert(VD->hasInit());
assert(CGM.getCodeGenOpts().hasReducedDebugInfo());
if (VD->hasAttr<NoDebugAttr>())
return;

auto &GV = DeclCache[VD];
if (GV)
return;

auto const *InitVal = VD->evaluateValue();
if (!InitVal)
return;

llvm::DIFile *Unit = nullptr;
llvm::DIScope *DContext = nullptr;
unsigned LineNo;
StringRef DeclName, LinkageName;
QualType T;
llvm::MDTuple *TemplateParameters = nullptr;
collectVarDeclProps(VD, Unit, LineNo, T, DeclName, LinkageName,
TemplateParameters, DContext);

auto Align = getDeclAlignIfRequired(VD, CGM.getContext());
llvm::DINodeArray Annotations = CollectBTFDeclTagAnnotations(VD);
llvm::DIExpression *InitExpr = createConstantValueExpression(VD, *InitVal);

GV.reset(DBuilder.createGlobalVariableExpression(
TheCU, DeclName, LinkageName, Unit, LineNo, getOrCreateType(T, Unit),
true, true, InitExpr, getOrCreateStaticDataMemberDeclarationOrNull(VD),
TemplateParameters, Align, Annotations));
}

void CGDebugInfo::EmitExternalVariable(llvm::GlobalVariable *Var,
const VarDecl *D) {
assert(CGM.getCodeGenOpts().hasReducedDebugInfo());
Expand Down Expand Up @@ -5890,18 +5866,6 @@ void CGDebugInfo::finalize() {
DBuilder.replaceTemporary(std::move(FwdDecl), cast<llvm::MDNode>(Repl));
}

for (auto const *VD : StaticDataMemberDefinitionsToEmit) {
assert(VD->isStaticDataMember());

if (DeclCache.contains(VD))
continue;

if (!VD->hasInit())
continue;

EmitGlobalVariable(VD);
}

// We keep our own list of retained types, because we need to look
// up the final type in the type cache.
for (auto &RT : RetainedTypes)
Expand Down
6 changes: 0 additions & 6 deletions clang/lib/CodeGen/CGDebugInfo.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -161,9 +161,6 @@ class CGDebugInfo {
llvm::DenseMap<const Decl *, llvm::TypedTrackingMDRef<llvm::DIDerivedType>>
StaticDataMemberCache;

/// Keeps track of static data members for which we should emit a definition.
std::vector<const VarDecl *> StaticDataMemberDefinitionsToEmit;

using ParamDecl2StmtTy = llvm::DenseMap<const ParmVarDecl *, const Stmt *>;
using Param2DILocTy =
llvm::DenseMap<const ParmVarDecl *, llvm::DILocalVariable *>;
Expand Down Expand Up @@ -529,9 +526,6 @@ class CGDebugInfo {
/// Emit a constant global variable's debug info.
void EmitGlobalVariable(const ValueDecl *VD, const APValue &Init);

/// Emit debug-info for a variable with a constant initializer.
void EmitGlobalVariable(const VarDecl *VD);

/// Emit information about an external variable.
void EmitExternalVariable(llvm::GlobalVariable *GV, const VarDecl *Decl);

Expand Down
13 changes: 4 additions & 9 deletions clang/test/CodeGenCXX/debug-info-class.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -116,19 +116,11 @@ int main(int argc, char **argv) {
// CHECK-SAME: DIFlagFwdDecl
// CHECK-NOT: identifier:
// CHECK-SAME: ){{$}}

// CHECK: !DIGlobalVariableExpression(var: ![[HDR_VAR:[0-9]+]], expr: !DIExpression(DW_OP_constu, 52, DW_OP_stack_value))
// CHECK: ![[HDR_VAR]] = distinct !DIGlobalVariable(name: "HdrSize",
// CHECK-SAME: isLocal: true, isDefinition: true, declaration: ![[HDR_VAR_DECL:[0-9]+]])
// CHECK: ![[INT:[0-9]+]] = !DIBasicType(name: "int"
// CHECK: ![[HDR_VAR_DECL]] = !DIDerivedType(tag: DW_TAG_member, name: "HdrSize"

// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "A"

// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "I"
// CHECK-NOT: DIFlagFwdDecl
// CHECK-SAME: ){{$}}

// CHECK: ![[INT:[0-9]+]] = !DIBasicType(name: "int"
// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "foo"
// CHECK: !DICompositeType(tag: DW_TAG_class_type, name: "bar"
// CHECK: !DICompositeType(tag: DW_TAG_union_type, name: "baz"
Expand Down Expand Up @@ -194,5 +186,8 @@ int main(int argc, char **argv) {
// CHECK: [[G_INNER_I]] = !DIDerivedType(tag: DW_TAG_member, name: "j"
// CHECK-SAME: baseType: ![[INT]]

// CHECK: !DICompositeType(tag: DW_TAG_structure_type, name: "A"
// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "HdrSize"
//
// CHECK: ![[EXCEPTLOC]] = !DILocation(line: 100,
// CHECK: ![[RETLOC]] = !DILocation(line: 99,
94 changes: 0 additions & 94 deletions clang/test/CodeGenCXX/debug-info-static-inline-member.cpp
View file

This file was deleted.

52 changes: 20 additions & 32 deletions clang/test/CodeGenCXX/debug-info-static-member.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -63,32 +63,32 @@ int C::a = 4;
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagStaticMember)
//
// CHECK: ![[CONST_A_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "const_a"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:

// CHECK: ![[CONST_B_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "const_b"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagProtected | DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "const_a"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagStaticMember,
// CHECK-SAME: extraData: i1 true)

// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "const_b"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagProtected | DIFlagStaticMember,
// CHECK-SAME: extraData: float 0x{{.*}})

// CHECK: ![[DECL_C:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "c"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagPublic | DIFlagStaticMember)
//
// CHECK: ![[CONST_C_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "const_c"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagPublic | DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "const_c"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagPublic | DIFlagStaticMember,
// CHECK-SAME: extraData: i32 18)
//
// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "x_a"
// CHECK-SAME: flags: DIFlagPublic | DIFlagStaticMember)
Expand Down Expand Up @@ -144,7 +144,7 @@ struct V {
// const_va is not emitted for MS targets.
// NOT-MS: !DIDerivedType(tag: DW_TAG_member, name: "const_va",
// NOT-MS-SAME: line: [[@LINE-5]]
// NOT-MS-NOT: extraData:
// NOT-MS-SAME: extraData: i32 42
const int V::const_va;

namespace x {
Expand All @@ -156,15 +156,3 @@ struct y {
};
int y::z;
}

// CHECK: !DIGlobalVariableExpression(var: ![[CONST_A_VAR:[0-9]+]], expr: !DIExpression(DW_OP_constu, 1, DW_OP_stack_value))
// CHECK: ![[CONST_A_VAR]] = distinct !DIGlobalVariable(name: "const_a"
// CHECK-SAME: isLocal: true, isDefinition: true, declaration: ![[CONST_A_DECL]])

// CHECK: !DIGlobalVariableExpression(var: ![[CONST_B_VAR:[0-9]+]], expr: !DIExpression(DW_OP_constu, {{.*}}, DW_OP_stack_value))
// CHECK: ![[CONST_B_VAR]] = distinct !DIGlobalVariable(name: "const_b"
// CHECK-SAME: isLocal: true, isDefinition: true, declaration: ![[CONST_B_DECL]])

// CHECK: !DIGlobalVariableExpression(var: ![[CONST_C_VAR:[0-9]+]], expr: !DIExpression(DW_OP_constu, 18, DW_OP_stack_value))
// CHECK: ![[CONST_C_VAR]] = distinct !DIGlobalVariable(name: "const_c"
// CHECK-SAME: isLocal: true, isDefinition: true, declaration: ![[CONST_C_DECL]])
63 changes: 1 addition & 62 deletions lldb/source/Plugins/SymbolFile/DWARF/DWARFASTParserClang.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -31,7 +31,6 @@
#include "lldb/Symbol/SymbolFile.h"
#include "lldb/Symbol/TypeList.h"
#include "lldb/Symbol/TypeMap.h"
#include "lldb/Symbol/VariableList.h"
#include "lldb/Target/Language.h"
#include "lldb/Utility/LLDBAssert.h"
#include "lldb/Utility/Log.h"
Expand Down Expand Up @@ -134,54 +133,6 @@ static lldb::ModuleSP GetContainingClangModule(const DWARFDIE &die) {
return lldb::ModuleSP();
}

std::optional<DWARFFormValue>
DWARFASTParserClang::FindConstantOnVariableDefinition(DWARFDIE die) {
assert(die.Tag() == llvm::dwarf::DW_TAG_member);

auto *dwarf = die.GetDWARF();
if (!dwarf)
return {};

ConstString name{die.GetName()};
if (!name)
return {};

auto *CU = die.GetCU();
if (!CU)
return {};

DWARFASTParser *dwarf_ast = dwarf->GetDWARFParser(*CU);
auto parent_decl_ctx = dwarf_ast->GetDeclContextContainingUIDFromDWARF(die);

// Make sure we populate the GetDieToVariable cache.
VariableList variables;
dwarf->FindGlobalVariables(name, parent_decl_ctx, UINT_MAX, variables);

// The cache contains the variable definition whose DW_AT_specification
// points to our declaration DIE. Look up that definition using our
// declaration.
auto const &die_to_var = dwarf->GetDIEToVariable();
auto it = die_to_var.find(die.GetDIE());
if (it == die_to_var.end())
return {};

auto var_sp = it->getSecond();
assert(var_sp != nullptr);

if (!var_sp->GetLocationIsConstantValueData())
return {};

auto def = dwarf->GetDIE(var_sp->GetID());
auto def_attrs = def.GetAttributes();
DWARFFormValue form_value;
if (!def_attrs.ExtractFormValueAtIndex(
def_attrs.FindAttributeIndex(llvm::dwarf::DW_AT_const_value),
form_value))
return {};

return form_value;
}

TypeSP DWARFASTParserClang::ParseTypeFromClangModule(const SymbolContext &sc,
const DWARFDIE &die,
Log *log) {
Expand Down Expand Up @@ -2955,21 +2906,9 @@ void DWARFASTParserClang::ParseSingleMember(

bool unused;
// TODO: Support float/double static members as well.
if (!ct.IsIntegerOrEnumerationType(unused))
if (!attrs.const_value_form || !ct.IsIntegerOrEnumerationType(unused))
return;

// Newer versions of Clang don't emit the DW_AT_const_value
// on the declaration of an inline static data member. Instead
// it's attached to the definition DIE. If that's the case,
// try and fetch it.
if (!attrs.const_value_form) {
auto maybe_form_value = FindConstantOnVariableDefinition(die);
if (!maybe_form_value)
return;

attrs.const_value_form = *maybe_form_value;
}

llvm::Expected<llvm::APInt> const_value_or_err =
ExtractIntFromFormValue(ct, *attrs.const_value_form);
if (!const_value_or_err) {
Expand Down
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