[PATCH] D45451: [ItaniumMangle] Undeduced auto type doesn't belong in the substitution table

[Erik Pilkington via Phabricator via cfe-commits]

erik.pilkington created this revision.
erik.pilkington added reviewers: rsmith, majnemer, rjmccall.

Since "Da" and "Dc" (auto and decltype(auto)) are under <builtin-type> in the mangling grammer, they shouldn't have a substitution (https://itanium-cxx-abi.github.io/cxx-abi/abi.html#mangling-compression). I believe that a deduced AutoType shouldn't be able to reach mangleType(AutoType) because it's deduced type would have been canonicalized in mangleType(QualType) before, so I removed that branch and added an assert. FWIW, with this patch applied Clang and GCC agree on the manglings in the affected file.

Thanks for taking a look!
Erik


Repository:
  rC Clang

https://reviews.llvm.org/D45451

Files:
  clang/lib/AST/ItaniumMangle.cpp
  clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp


Index: clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
===================================================================
--- clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
+++ clang/test/CodeGenCXX/lambda-expressions-inside-auto-functions.cpp
@@ -52,10 +52,10 @@
   
   template<class T> auto foo() { return [](const T&) { return 42; }; }
 };
-//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIdE14default_lambdaIdEEDavENKUlRKdE_clES5_(%class.anon
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIdE14default_lambdaIdEEDavENKUlRKdE_clES4_(%class.anon
 int run2 = A<double>{}.func()(3.14);
 
-//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIcE14default_lambdaIcEEDavENKUlRKcE_clES5_(%class.anon
+//CHECK-LABEL: define linkonce_odr i32 @_ZZN22inline_member_function1AIcE14default_lambdaIcEEDavENKUlRKcE_clES4_(%class.anon
 int run3 = A<char>{}.func()('a');
 } // end inline_member_function
 
Index: clang/lib/AST/ItaniumMangle.cpp
===================================================================
--- clang/lib/AST/ItaniumMangle.cpp
+++ clang/lib/AST/ItaniumMangle.cpp
@@ -2338,7 +2338,8 @@
     return true;
   if (Ty->isBuiltinType())
     return false;
-
+  if (isa<AutoType>(Ty))
+    return false;
   return true;
 }
 
@@ -3250,14 +3251,13 @@
 }
 
 void CXXNameMangler::mangleType(const AutoType *T) {
-  QualType D = T->getDeducedType();
-  // <builtin-type> ::= Da  # dependent auto
-  if (D.isNull()) {
-    assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
-           "shouldn't need to mangle __auto_type!");
-    Out << (T->isDecltypeAuto() ? "Dc" : "Da");
-  } else
-    mangleType(D);
+  assert(T->getDeducedType().isNull() &&
+         "Deduced AutoType shouldn't be handled here!");
+  assert(T->getKeyword() != AutoTypeKeyword::GNUAutoType &&
+         "shouldn't need to mangle __auto_type!");
+  // <builtin-type> ::= Da # auto
+  //                ::= Dc # decltype(auto)
+  Out << (T->isDecltypeAuto() ? "Dc" : "Da");
 }
 
 void CXXNameMangler::mangleType(const DeducedTemplateSpecializationType *T) {


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