[llvm-cxxfilt] Do not consider the prefix dot as part of the demangled symbol name.

Summary:

In AIX OS, function entry label are begin with '.', it can not be decoded currently.
we support to decode the name in this patch for all OS.

Reviewers: Fangrui Song, James Henderson,
Differential Revision: https://reviews.llvm.org/D139864

Author: diggerlin

llvm/include/llvm/Demangle/Demangle.h

@@ -67,7 +67,8 @@ char *dlangDemangle(std::string_view MangledName);
 /// demangling occurred.
 std::string demangle(std::string_view MangledName);
 
-bool nonMicrosoftDemangle(std::string_view MangledName, std::string &Result);
+bool nonMicrosoftDemangle(std::string_view MangledName, std::string &Result,
+                          bool CanHaveLeadingDot = true);
 
 /// "Partial" demangler. This supports demangling a string into an AST
 /// (typically an intermediate stage in itaniumDemangle) and querying certain

llvm/lib/Demangle/Demangle.cpp

@@ -24,7 +24,8 @@ std::string llvm::demangle(std::string_view MangledName) {
     return Result;
 
   if (starts_with(MangledName, '_') &&
-      nonMicrosoftDemangle(MangledName.substr(1), Result))
+      nonMicrosoftDemangle(MangledName.substr(1), Result,
+                           /*CanHaveLeadingDot=*/false))
     return Result;
 
   if (char *Demangled = microsoftDemangle(MangledName, nullptr, nullptr)) {
@@ -46,8 +47,15 @@ static bool isRustEncoding(std::string_view S) { return starts_with(S, "_R"); }
 static bool isDLangEncoding(std::string_view S) { return starts_with(S, "_D"); }
 
 bool llvm::nonMicrosoftDemangle(std::string_view MangledName,
-                                std::string &Result) {
+                                std::string &Result, bool CanHaveLeadingDot) {
   char *Demangled = nullptr;
+
+  // Do not consider the dot prefix as part of the demangled symbol name.
+  if (CanHaveLeadingDot && MangledName.size() > 0 && MangledName[0] == '.') {
+    MangledName.remove_prefix(1);
+    Result = ".";
+  }
+
   if (isItaniumEncoding(MangledName))
     Demangled = itaniumDemangle(MangledName);
   else if (isRustEncoding(MangledName))
@@ -58,7 +66,7 @@ bool llvm::nonMicrosoftDemangle(std::string_view MangledName,
   if (!Demangled)
     return false;
 
-  Result = Demangled;
+  Result += Demangled;
   std::free(Demangled);
   return true;
 }

llvm/test/tools/llvm-cxxfilt/delimiters.test

@@ -32,7 +32,7 @@ RUN:      '_Z3Foo,,_Z3Bar::_Z3Baz  _Z3Foo,_Z3Bar:_Z3Baz' \
 COM: Piping the echo output causes '⦙' to be converted to '?' in some
 COM: builds/environments. Redirect echo output to and from %t to work
 COM: around this. See D111072.
-RUN:      '_Z3Foo$ ._Z3Foo' > %t
+RUN:      '_Z3Foo$ Foo._Z3Bar' > %t
 RUN:      llvm-cxxfilt -n < %t | FileCheck %s
 
 CHECK: ,,Foo!
@@ -66,4 +66,4 @@ CHECK: Foo}
 CHECK: Foo~,,
 CHECK: Foo⦙Bar
 CHECK: Foo,,Bar::Baz  Foo,Bar:Baz
-CHECK: _Z3Foo$ ._Z3Foo
+CHECK: _Z3Foo$ Foo._Z3Bar

llvm/test/tools/llvm-cxxfilt/dot-prefix.test

@@ -0,0 +1,4 @@
+## Show that the llvm-cxxfilt does not consider the dot prefix to be part of the symbol name to be demangled.
+RUN: llvm-cxxfilt -n ._ZL5func0v | FileCheck %s
+
+CHECK: .func0()

llvm/test/tools/llvm-cxxfilt/strip-underscore.test

@@ -1,15 +1,17 @@
 ## Show the behaviour of --[no-]strip-underscore. This test does not test
 ## the platform-specific default behaviour. This is tested elsewhere.
 
-RUN: llvm-cxxfilt -_ __ZN2ns1fE _ZSt1f _f | FileCheck %s -check-prefix CHECK-STRIPPED
-RUN: llvm-cxxfilt --strip-underscore __ZN2ns1fE _ZSt1f _f | FileCheck %s -check-prefix CHECK-STRIPPED
-RUN: llvm-cxxfilt -n __ZN2ns1fE _ZSt1f _f | FileCheck %s -check-prefix CHECK-UNSTRIPPED
-RUN: llvm-cxxfilt --no-strip-underscore __ZN2ns1fE _ZSt1f _f | FileCheck %s -check-prefix CHECK-UNSTRIPPED
+RUN: llvm-cxxfilt -_ __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-STRIPPED
+RUN: llvm-cxxfilt --strip-underscore __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-STRIPPED
+RUN: llvm-cxxfilt -n __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-UNSTRIPPED
+RUN: llvm-cxxfilt --no-strip-underscore __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-UNSTRIPPED
 
 CHECK-STRIPPED: ns::f
 CHECK-STRIPPED: _ZSt1f
 CHECK-STRIPPED: _f
+CHECK-STRIPPED: ._Z3f.0v
 
 CHECK-UNSTRIPPED: __ZN2ns1fE
 CHECK-UNSTRIPPED: std::f
 CHECK-UNSTRIPPED: _f
+CHECK-UNSTRIPPED: _._Z3f.0v

llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp

@@ -67,12 +67,14 @@ static void error(const Twine &Message) {
 static std::string demangle(const std::string &Mangled) {
   using llvm::itanium_demangle::starts_with;
   std::string_view DecoratedStr = Mangled;
-  if (StripUnderscore)
-    if (DecoratedStr[0] == '_')
-      DecoratedStr.remove_prefix(1);
+  bool CanHaveLeadingDot = true;
+  if (StripUnderscore && DecoratedStr[0] == '_') {
+    DecoratedStr.remove_prefix(1);
+    CanHaveLeadingDot = false;
+  }
 
   std::string Result;
-  if (nonMicrosoftDemangle(DecoratedStr, Result))
+  if (nonMicrosoftDemangle(DecoratedStr, Result, CanHaveLeadingDot))
     return Result;
 
   std::string Prefix;