[clang] [clang][DebugInfo] Revert to printing canonical typenames for template aliases (PR #110767)
via cfe-commits
cfe-commits at lists.llvm.org
Tue Oct 1 16:57:21 PDT 2024
llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang
Author: Michael Buch (Michael137)
<details>
<summary>Changes</summary>
This was originally added in https://reviews.llvm.org/D142268 have LLDB display variable typenames that benefit from suppressing defaulted template arguments.
We currently represent template aliases as `DW_AT_typedef`s instead of `DW_TAG_template_alias`. This means for types like:
```
template <class _Tp>
using __remove_cv_t = __remove_cv(_Tp);
template <class _Tp>
using remove_cv_t = __remove_cv_t<_Tp>;
template<typename T>
class optional {
using value_type = T;
remove_cv_t<value_type> __val_;
}
```
we would generate DWARF like:
```
0x0000274f: DW_TAG_typedef
DW_AT_type (0x0000000000002758 "__remove_cv_t<value_type>")
DW_AT_name ("remove_cv_t<value_type>")
```
This is an actual libc++ type layout introduced in https://github.com/llvm/llvm-project/pull/110355, which uncovered a shortcoming of LLDB's data-formatter infrastructure, which caches formatters on the contents of `DW_AT_name`.
To unblock the libc++ change, I think we can revert this without much fallout.
Then we have two options for follow-up (or do both):
1. reland this but adjust the LLDB formatter cache so it doesn't cache formatters for template specializations
2. implement support for `DW_TAG_template_alias` in LLDB (and make Clang generate them by default).
---
Full diff: https://github.com/llvm/llvm-project/pull/110767.diff
2 Files Affected:
- (modified) clang/lib/CodeGen/CGDebugInfo.cpp (-9)
- (modified) clang/test/CodeGenCXX/debug-info-alias.cpp (+1-1)
``````````diff
diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 8887c4de7c4c81..609957b75d6e7e 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -1472,15 +1472,6 @@ llvm::DIType *CGDebugInfo::CreateType(const TemplateSpecializationType *Ty,
return AliasTy;
}
- // Disable PrintCanonicalTypes here because we want
- // the DW_AT_name to benefit from the TypePrinter's ability
- // to skip defaulted template arguments.
- //
- // FIXME: Once -gsimple-template-names is enabled by default
- // and we attach template parameters to alias template DIEs
- // we don't need to worry about customizing the PrintingPolicy
- // here anymore.
- PP.PrintCanonicalTypes = false;
printTemplateArgumentList(OS, Ty->template_arguments(), PP,
TD->getTemplateParameters());
return DBuilder.createTypedef(Src, OS.str(), getOrCreateFile(Loc),
diff --git a/clang/test/CodeGenCXX/debug-info-alias.cpp b/clang/test/CodeGenCXX/debug-info-alias.cpp
index bf2dbee4659592..3cd1446d25270e 100644
--- a/clang/test/CodeGenCXX/debug-info-alias.cpp
+++ b/clang/test/CodeGenCXX/debug-info-alias.cpp
@@ -24,7 +24,7 @@ x::bar<int> bi;
// CHECK: [[BFLOAT]] = !DIDerivedType(tag: DW_TAG_typedef, name: "bar<float>"
x::bar<float> bf;
// CHECK: !DIGlobalVariable(name: "bz",{{.*}} type: [[BBAZ:![0-9]+]]
-// CHECK: [[BBAZ]] = !DIDerivedType(tag: DW_TAG_typedef, name: "bar<baz<int> >"
+// CHECK: [[BBAZ]] = !DIDerivedType(tag: DW_TAG_typedef, name: "bar<baz<int, int> >"
x::bar<baz<int>> bz;
using
``````````
</details>
https://github.com/llvm/llvm-project/pull/110767
More information about the cfe-commits
mailing list