[IRForTarget] Strenghten handling of alternate mangling.

Summary:
This fixes an issue with GCC generated binaries wherein an expression
with method invocations on std::string variables was failing. Such use
cases are tested in TestSTL (albeit, in a test marked with
@unittest2.expectedFailure because of other reasons).

The reason for this particular failure with GCC is that the generated
DWARF for std::basic_string<...> is incomplete, which makes clang not
to use the alternate mangling scheme. GCC correctly generates the name
of basic_string<...>:

DW_AT_name "basic_string<char, std::char_traits<char>, std::allocator<char> >"

It also lists the template parameters of basic_string correctly:

DW_TAG_template_type_parameter
    DW_AT_name                  "_CharT"
    DW_AT_type                  <0x0000009c>
DW_TAG_template_type_parameter
    DW_AT_name                  "_Traits"
    DW_AT_type                  <0x00000609>
DW_TAG_template_type_parameter
    DW_AT_name                  "_Alloc"
    DW_AT_type                  <0x000007fb>

However, it does not list the template parameters of std::char_traits<>.
This makes Clang feel (while parsing the expression) that the string
variable is not actually a basic_string instance, and consequently does
not use the alternate mangling scheme.

Test Plan:
dotest.py -C gcc -p TestSTL
          -- See it go past the "for" loop expression successfully.

Reviewers: clayborg, spyffe

Reviewed By: clayborg, spyffe

Subscribers: tberghammer, zturner, lldb-commits

Differential Revision: http://reviews.llvm.org/D8846

llvm-svn: 234522

2 files changed, 51 insertions, 0 deletions

diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp
index 50537eb119f..5712b208855 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.cpp
@@ -281,9 +281,43 @@ ItaniumABILanguageRuntime::IsVTableName (const char *name)
         return false;
 }
 
+size_t
+ItaniumABILanguageRuntime::GetAlternateManglings(const ConstString &mangled, std::vector<ConstString> &alternates)
+{
+    if (!mangled)
+        return static_cast<size_t>(0);
+
+    alternates.clear();
+    const char *mangled_cstr = mangled.AsCString();
+    for (typename std::map<ConstString, std::vector<ConstString> >::iterator it = s_alternate_mangling_prefixes.begin();
+         it != s_alternate_mangling_prefixes.end();
+         ++it)
+    {
+        const char *prefix_cstr = it->first.AsCString();
+        if (strncmp(mangled_cstr, prefix_cstr, strlen(prefix_cstr)) == 0)
+        {
+            const std::vector<ConstString> &alternate_prefixes = it->second;
+            for (size_t i = 0; i < alternate_prefixes.size(); ++i)
+            {
+                std::string alternate_mangling(alternate_prefixes[i].AsCString());
+                alternate_mangling.append(mangled_cstr + strlen(prefix_cstr));
+
+                alternates.push_back(ConstString(alternate_mangling.c_str()));
+            }
+
+            return alternates.size();
+        }
+    }
+
+    return static_cast<size_t>(0);
+}
+
 //------------------------------------------------------------------
 // Static Functions
 //------------------------------------------------------------------
+
+std::map<ConstString, std::vector<ConstString> > ItaniumABILanguageRuntime::s_alternate_mangling_prefixes;
+
 LanguageRuntime *
 ItaniumABILanguageRuntime::CreateInstance (Process *process, lldb::LanguageType language)
 {
@@ -304,6 +338,15 @@ ItaniumABILanguageRuntime::Initialize()
     PluginManager::RegisterPlugin (GetPluginNameStatic(),
                                    "Itanium ABI for the C++ language",
                                    CreateInstance);    
+
+    // Alternate manglings for std::basic_string<...>
+    std::vector<ConstString> basic_string_alternates;
+    basic_string_alternates.push_back(ConstString("_ZNSs"));
+    basic_string_alternates.push_back(ConstString("_ZNKSs"));
+    s_alternate_mangling_prefixes[ConstString("_ZNSbIcSt17char_traits<char>St15allocator<char>E")] =
+        basic_string_alternates;
+    s_alternate_mangling_prefixes[ConstString("_ZNKSbIcSt17char_traits<char>St15allocator<char>E")] =
+        basic_string_alternates;
 }
 
 void
diff --git a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.h b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.h
index cd0a4b2c15e..d1dbb7ad407 100644
--- a/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.h
+++ b/lldb/source/Plugins/LanguageRuntime/CPlusPlus/ItaniumABI/ItaniumABILanguageRuntime.h
@@ -20,6 +20,9 @@
 #include "lldb/Target/CPPLanguageRuntime.h"
 #include "lldb/Core/Value.h"
 
+#include <map>
+#include <vector>
+
 namespace lldb_private {
     
     class ItaniumABILanguageRuntime :
@@ -82,6 +85,9 @@ namespace lldb_private {
         virtual lldb::SearchFilterSP
         CreateExceptionSearchFilter ();
 
+        virtual size_t
+        GetAlternateManglings(const ConstString &mangled, std::vector<ConstString> &alternates);
+
     protected:
 
         lldb::BreakpointResolverSP
@@ -97,6 +103,8 @@ namespace lldb_private {
         ItaniumABILanguageRuntime(Process *process) : lldb_private::CPPLanguageRuntime(process) { } // Call CreateInstance instead.
         
         lldb::BreakpointSP                              m_cxx_exception_bp_sp;
+
+        static std::map<ConstString, std::vector<ConstString> > s_alternate_mangling_prefixes;
     };
     
 } // namespace lldb_private