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[clang][DebugInfo] Revert to attaching DW_AT_const_value on static me…
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…mber declarations (#73626)

In #71780 we started emitting
definitions for all static data-members with constant initialisers, even
if they were constants (i.e., didn't have a location). We also dropped
the DW_AT_const_value from the declaration to [help resolve
inconsistencies during type merging in the
DWARFParallelLinker](#68721).
However, for static data members that do have locations, we wouldn't
emit a DW_AT_const_value on it, assuming that the consumer knows how to
read the value using the location. This broke some consumers that really
wanted to find a DW_AT_const_value. Ultimately we want to attach a
DW_AT_const_value to definitions that have a location too. But to fix
consumers broken by said change, this patch adds the constant back onto
the declaration. This is what we used to do prior to
#71780
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@Michael137
Michael137 authored Nov 28, 2023
1 parent f3a9dbe commit 7f3ee3c
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Showing 3 changed files with 26 additions and 14 deletions.
18 changes: 15 additions & 3 deletions clang/lib/CodeGen/CGDebugInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1680,14 +1680,26 @@ CGDebugInfo::CreateRecordStaticField(const VarDecl *Var, llvm::DIType *RecordTy,
unsigned LineNumber = getLineNumber(Var->getLocation());
StringRef VName = Var->getName();

// FIXME: to avoid complications with type merging we should
// emit the constant on the definition instead of the declaration.
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 Tag = CGM.getCodeGenOpts().DwarfVersion >= 5
? llvm::dwarf::DW_TAG_variable
: llvm::dwarf::DW_TAG_member;
auto Align = getDeclAlignIfRequired(Var, CGM.getContext());
llvm::DIDerivedType *GV =
DBuilder.createStaticMemberType(RecordTy, VName, VUnit, LineNumber, VTy,
Flags, /* Val */ nullptr, Tag, Align);
llvm::DIDerivedType *GV = DBuilder.createStaticMemberType(
RecordTy, VName, VUnit, LineNumber, VTy, Flags, C, Tag, Align);
StaticDataMemberCache[Var->getCanonicalDecl()].reset(GV);
StaticDataMemberDefinitionsToEmit.push_back(Var->getCanonicalDecl());
return GV;
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14 changes: 7 additions & 7 deletions clang/test/CodeGenCXX/debug-info-static-inline-member.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -49,35 +49,35 @@ int main() {

// CHECK: ![[INT_DECL]] = !DIDerivedType(tag: DW_TAG_member, name: "cexpr_int_with_addr",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 25

// CHECK: ![[INT_DECL2:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "cexpr_int2",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 26

// CHECK: ![[FLOAT_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "cexpr_float",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: float

// CHECK: ![[ENUM_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "cexpr_enum",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 -1

// CHECK: ![[EMPTY_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "cexpr_struct_with_addr",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:

// CHECK: ![[IENUM_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "inline_enum",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 -1

// CHECK: ![[EMPTY_TEMPLATED_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "empty_templated",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 1

// CHECK: ![[TEMPLATE_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "cexpr_template",
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 1

// CHECK: !DIGlobalVariableExpression(var: ![[EMPTY_VAR:[0-9]+]], expr: !DIExpression())
// CHECK: ![[EMPTY_VAR]] = distinct !DIGlobalVariable(name: "cexpr_struct_with_addr", linkageName:
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8 changes: 4 additions & 4 deletions clang/test/CodeGenCXX/debug-info-static-member.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -74,15 +74,15 @@ int C::a = 4;
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i1 true

// DWARF4: ![[CONST_B_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "const_b"
// DWARF5: ![[CONST_B_DECL:[0-9]+]] = !DIDerivedType(tag: DW_TAG_variable, name: "const_b"
// CHECK-NOT: size:
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagProtected | DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: float

// DWARF4: ![[DECL_C:[0-9]+]] = !DIDerivedType(tag: DW_TAG_member, name: "c"
// DWARF5: ![[DECL_C:[0-9]+]] = !DIDerivedType(tag: DW_TAG_variable, name: "c"
Expand All @@ -97,7 +97,7 @@ int C::a = 4;
// CHECK-NOT: align:
// CHECK-NOT: offset:
// CHECK-SAME: flags: DIFlagPublic | DIFlagStaticMember
// CHECK-NOT: extraData:
// CHECK-SAME: extraData: i32 18
//
// DWARF4: !DIDerivedType(tag: DW_TAG_member, name: "x_a"
// DWARF5: !DIDerivedType(tag: DW_TAG_variable, name: "x_a"
Expand Down Expand Up @@ -154,7 +154,7 @@ 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 {
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