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[Clang] Fall back to DW_TAG_typedef for instantiation dependent template aliases #90032

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Merged
merged 1 commit into from
Apr 25, 2024
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[Clang] Fall back to DW_TAG_typedef for instantiation dependent template aliases #90032

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21 changes: 20 additions & 1 deletion clang/lib/CodeGen/CGDebugInfo.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -1372,7 +1372,26 @@ llvm::DIType *CGDebugInfo::CreateType(const TemplateSpecializationType *Ty,

SourceLocation Loc = AliasDecl->getLocation();

if (CGM.getCodeGenOpts().DebugTemplateAlias) {
if (CGM.getCodeGenOpts().DebugTemplateAlias &&
// The TemplateSpecializationType doesn't contain any instantiation
// information; dependent template arguments can't be resolved. For now,
// fall back to DW_TAG_typedefs for template aliases that are
// instantiation dependent, e.g.:
// ```
// template <int>
// using A = int;
//
// template<int I>
// struct S {
// using AA = A<I>; // Instantiation dependent.
// AA aa;
// };
//
// S<0> s;
// ```
// S::AA's underlying type A<I> is dependent on I so will be emitted as a
// DW_TAG_typedef.
!Ty->isInstantiationDependentType()) {
auto ArgVector = ::GetTemplateArgs(TD, Ty);
TemplateArgs Args = {TD->getTemplateParameters(), ArgVector};

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21 changes: 21 additions & 0 deletions clang/test/CodeGenCXX/dependent-template-alias.cpp
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@@ -0,0 +1,21 @@
// RUN: %clang_cc1 -triple x86_64-unk-unk -o - -emit-llvm -debug-info-kind=standalone -gtemplate-alias %s -gsimple-template-names=simple \
// RUN: | FileCheck %s

//// Check that -gtemplate-alias falls back to DW_TAG_typedef emission
//// for instantiation dependent type aliases.

template <int>
using A = int;

template<int I>
struct S {
using AA = A<I>;
AA aa;
};

S<0> s;

// CHECK: !DIDerivedType(tag: DW_TAG_member, name: "aa", scope: ![[#]], file: ![[#]], line: [[#]], baseType: ![[AA:[0-9]+]], size: 32)
// CHECK: [[AA]] = !DIDerivedType(tag: DW_TAG_typedef, name: "AA", file: ![[#]], line: [[#]], baseType: ![[A:[0-9]+]])
// CHECK: [[A]] = !DIDerivedType(tag: DW_TAG_typedef, name: "A<I>", file: ![[#]], line: [[#]], baseType: ![[int:[0-9]+]])
// CHECK: [[int]] = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)