[gmodules] Skip CXXDeductionGuideDecls when visiting FunctionDecls in DebugTypeVisitor

[ahatanak]

Summary

rdar://92845517

[ahatanak]

Without this fix, CXXNameMangler::mangleUnresolvedName crashes when it tries to mangle the name of a CXXDeductionGuideDecl.

[ahatanak]

ping.

Does debug info need information on deduction guides? I think it's safe to skip deduction guides as they are used only for template argument deduction.

[aprantl]

Adding the debug-info group. I don't really know enough about deduction guides to comment on the implications, but if it fixes the crash it seems to be a strict improvement. Maybe wait another day to see if someone else has an opinion on this.

[kaz7]

Hi, after this patch, our buildbot for VE having errors like https://lab.llvm.org/buildbot/#/builders/91/builds/9984.

When I run a test script by hand, it shows following errors. Please investigate them. Thank you.

$ cd build
$ /home/marukawa/llvm-upstream/build/bin/clang -cc1 -internal-isystem /home/marukawa/llvm-upstream/build/lib/clang/15.0.0/include -nostdsysteminc -std=c++2b -x c++-header -emit-pch -fmodule-format=obj -I /home/marukawa/llvm-upstream/llvm-project/clang/test/Modules/Inputs    -o /home/marukawa/llvm-upstream/build/tools/clang/test/Modules/Output/gmodules-deduction-guide.cpp.tmp.pch /home/marukawa/llvm-upstream/llvm-project/clang/test/Modules/Inputs/gmodules-deduction-guide.h    -mllvm -debug-only=pchcontainer &>/home/marukawa/llvm-upstream/build/tools/clang/test/Modules/Output/gmodules-deduction-guide.cpp.tmp-pch.ll
$ echo $?
1
$ cat /home/marukawa/llvm-upstream/build/tools/clang/test/Modules/Output/gmodules-deduction-guide.cpp.tmp-pch.ll | /home/marukawa/llvm-upstream/build/bin/FileCheck /home/marukawa/llvm-upstream/llvm-project/clang/test/Modules/gmodules-deduction-guide.cpp
/home/marukawa/llvm-upstream/llvm-project/clang/test/Modules/gmodules-deduction-guide.cpp:6:11: error: CHECK: expected string not found in input
// CHECK: ![[V0:.*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S<A>",
          ^
<stdin>:1:1: note: scanning from here
clang (LLVM option parsing): Unknown command line argument '-debug-only=pchcontainer'. Try: 'clang (LLVM option parsing) --help'
^

Input file: <stdin>
Check file: /home/marukawa/llvm-upstream/llvm-project/clang/test/Modules/gmodules-deduction-guide.cpp

-dump-input=help explains the following input dump.

Input was:
<<<<<<
         1: clang (LLVM option parsing): Unknown command line argument '-debug-only=pchcontainer'. Try: 'clang (LLVM option parsing) --help'
check:6     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
         2: clang (LLVM option parsing): Did you mean '--debug-pass=pchcontainer'?
check:6     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>>>>>

[chapuni]

clang/test/Modules/gmodules-deduction-guide.cpp

3

FYI, it is unavailable with -Asserts

[ahatanak]

clang/test/Modules/gmodules-deduction-guide.cpp

3

Ah, right. Thank you!

[kaz7]

Thank you, @chapuni and @ahatanak, for quick fixing.

clang/lib/CodeGen/ObjectFilePCHContainerOperations.cpp

struct DebugTypeVisitor : public RecursiveASTVisitor<DebugTypeVisitor> {
     bool VisitObjCInterfaceDecl(ObjCInterfaceDecl *D) {
       QualType QualTy(D->getTypeForDecl(), 0);
       if (!QualTy.isNull() && CanRepresent(QualTy.getTypePtr()))
         DI.getOrCreateStandaloneType(QualTy, D->getLocation());
       return true;
     }
 
     bool VisitFunctionDecl(FunctionDecl *D) {
+      // Skip deduction guides.
+      if (isa<CXXDeductionGuideDecl>(D))
+        return true;
+
       if (isa<CXXMethodDecl>(D))
         // This is not yet supported. Constructing the `this' argument
         // mandates a CodeGenFunction.
         return true;
 
       SmallVector<QualType, 16> ArgTypes;
       for (auto i : D->parameters())
         ArgTypes.push_back(i->getType());

clang/test/Modules/Inputs/gmodules-deduction-guide.h

+struct A {
+};
+
+template <class T>
+struct S{
+  S(const A &);
+};
+
+S(const A&) -> S<A>;
+
+typedef decltype(S(A())) Type0;

clang/test/Modules/gmodules-deduction-guide.cpp

+// RUN: %clang_cc1 -std=c++2b -x c++-header -emit-pch -fmodule-format=obj -I %S/Inputs \
+// RUN:   -o %t.pch %S/Inputs/gmodules-deduction-guide.h \
+// RUN:   -mllvm -debug-only=pchcontainer &>%t-pch.ll
+// RUN: cat %t-pch.ll | FileCheck %s
+
+// CHECK: ![[V0:.*]] = distinct !DICompositeType(tag: DW_TAG_structure_type, name: "S<A>",
+// CHECK: !DIDerivedType(tag: DW_TAG_typedef, name: "Type0",{{.*}}, baseType: ![[V0]])