[clang] 87ec4ab - [Clang] Fall back to DW_TAG_typedef for instantiation dependent template aliases (#90032)
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Thu Apr 25 02:34:36 PDT 2024
Author: Orlando Cazalet-Hyams
Date: 2024-04-25T10:34:32+01:00
New Revision: 87ec4ab72cb3ae27ac08d040b2825ee01214fe75
URL: https://github.com/llvm/llvm-project/commit/87ec4ab72cb3ae27ac08d040b2825ee01214fe75
DIFF: https://github.com/llvm/llvm-project/commit/87ec4ab72cb3ae27ac08d040b2825ee01214fe75.diff
LOG: [Clang] Fall back to DW_TAG_typedef for instantiation dependent template aliases (#90032)
Workaround for issue #89774 until it can be properly fixed.
When `-gtemplate-alias` is specified Clang emits a DW_TAG_template_alias
for template aliases. This patch avoids an assertion failure by falling
back to the `-gno-template-alias` (default) behaviour, emitting a
DW_TAG_typedef, if the alias is instantiation dependent.
Added:
clang/test/CodeGenCXX/dependent-template-alias.cpp
Modified:
clang/lib/CodeGen/CGDebugInfo.cpp
Removed:
################################################################################
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 539ded5cca5e1b..787db350487417 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -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};
diff --git a/clang/test/CodeGenCXX/dependent-template-alias.cpp b/clang/test/CodeGenCXX/dependent-template-alias.cpp
new file mode 100644
index 00000000000000..deb243f9fc88d0
--- /dev/null
+++ b/clang/test/CodeGenCXX/dependent-template-alias.cpp
@@ -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)
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