Improved name demangling performance by 20% on darwin. (e41e5899) · Commits · llvm-doe / llvm-project

lldb/include/lldb/Core/ConstString.h

+5 −1

Original line number	Diff line number	Diff line
		@@ -290,7 +290,11 @@ public:
		/// @li \b false if the contained string is not empty.
		//------------------------------------------------------------------
		bool
		IsEmpty () const;
		IsEmpty () const
		{
		return m_string == NULL \|\| m_string[0] == '\0';
		}


		//------------------------------------------------------------------
		/// Set the C string value.

lldb/lldb.xcodeproj/project.pbxproj

+1 −0

Original line number	Diff line number	Diff line
		@@ -2295,6 +2295,7 @@
		isa = PBXProject;
		buildConfigurationList = 1DEB91EF08733DB70010E9CD /* Build configuration list for PBXProject "lldb" */;
		compatibilityVersion = "Xcode 3.1";
		developmentRegion = English;
		hasScannedForEncodings = 1;
		knownRegions = (
		en,

lldb/source/Core/ConstString.cpp

+0 −9

Original line number	Diff line number	Diff line
		@@ -390,15 +390,6 @@ ConstString::DumpDebug(Stream *s) const
		s->Printf("%p: ConstString, string = %s%s%s, length = %zu", (int)sizeof(void) * 2, this, parens, cstr, parens, cstr_len);
		}

		//----------------------------------------------------------------------
		// Returns true if the contained string is empty.
		//----------------------------------------------------------------------
		bool
		ConstString::IsEmpty() const
		{
		return m_string == NULL \|\| m_string[0] == '\0';
		}

		//----------------------------------------------------------------------
		// Set the string value in the object by uniquing the "cstr" string
		// value in our global string pool.

lldb/source/Core/Mangled.cpp

+39 −8

Original line number	Diff line number	Diff line
		@@ -9,6 +9,8 @@

		#include <cxxabi.h>

		#include "llvm/ADT/DenseMap.h"

		#include "lldb/Core/ConstString.h"
		#include "lldb/Core/Mangled.h"
		#include "lldb/Core/Stream.h"
		@@ -142,11 +144,39 @@ Mangled::GetDemangledName () const
		const char * mangled = m_mangled.AsCString();
		if (mangled[0])
		{
		// Since demangling can be a costly, and since all names that go
		// into a ConstString (like our m_mangled and m_demangled members)
		// end up being unique "const char *" values, we can use a DenseMap
		// to speed up our lookup. We do this because often our symbol table
		// and our debug information both have the mangled names which they
		// would each need to demangle. Also, with GCC we end up with the one
		// definition rule where a lot of STL code produces symbols that are
		// in multiple compile units and the mangled names end up being in
		// the same binary multiple times. The performance win isn't huge,
		// but we showed a 20% improvement on darwin.
		typedef llvm::DenseMap<const char , const char > MangledToDemangledMap;
		static MangledToDemangledMap g_mangled_to_demangled;

		// Check our mangled string pointer to demangled string pointer map first
		MangledToDemangledMap::const_iterator pos = g_mangled_to_demangled.find (mangled);
		if (pos != g_mangled_to_demangled.end())
		{
		// We have already demangled this string, we can just use our saved result!
		m_demangled.SetCString(pos->second);
		}
		else
		{
		// We didn't already mangle this name, demangle it and if all goes well
		// add it to our map.
		char *demangled_name = abi::__cxa_demangle (mangled, NULL, NULL, NULL);

		if (demangled_name)
		{
		m_demangled.SetCString (demangled_name);
		// Now that the name has been uniqued, add the uniqued C string
		// pointer from m_mangled as the key to the uniqued C string
		// pointer in m_demangled.
		g_mangled_to_demangled.insert (std::make_pair (mangled, m_demangled.GetCString()));
		free (demangled_name);
		}
		else
		@@ -157,6 +187,7 @@ Mangled::GetDemangledName () const
		}
		}
		}
		}

		return m_demangled;
		}

lldb/source/Plugins/SymbolFile/DWARF/DWARFCompileUnit.cpp

+11 −6

Original line number	Diff line number	Diff line
		@@ -9,6 +9,7 @@

		#include "DWARFCompileUnit.h"

		#include "lldb/Core/Mangled.h"
		#include "lldb/Core/Stream.h"
		#include "lldb/Core/Timer.h"

		@@ -591,7 +592,7 @@ DWARFCompileUnit::Index

		DWARFDebugInfoEntry::Attributes attributes;
		const char *name = NULL;
		const char *mangled = NULL;
		Mangled mangled;
		bool is_variable = false;
		bool is_declaration = false;
		bool is_artificial = false;
		@@ -629,7 +630,7 @@ DWARFCompileUnit::Index

		case DW_AT_MIPS_linkage_name:
		if (attributes.ExtractFormValueAtIndex(m_dwarf2Data, i, form_value))
		mangled = form_value.AsCString(debug_str);
		mangled.GetMangledName().SetCString(form_value.AsCString(debug_str));
		break;

		case DW_AT_low_pc:
		@@ -761,8 +762,10 @@ DWARFCompileUnit::Index
		else
		base_name_to_function_die.Append(ConstString(name).AsCString(), die.GetOffset());
		}
		if (mangled)
		full_name_to_function_die.Append(ConstString(mangled).AsCString(), die.GetOffset());
		if (mangled.GetMangledName())
		full_name_to_function_die.Append(mangled.GetMangledName().AsCString(), die.GetOffset());
		if (mangled.GetDemangledName())
		full_name_to_function_die.Append(mangled.GetDemangledName().AsCString(), die.GetOffset());
		}
		break;

		@@ -771,8 +774,10 @@ DWARFCompileUnit::Index
		{
		if (name)
		base_name_to_function_die.Append(ConstString(name).AsCString(), die.GetOffset());
		if (mangled)
		full_name_to_function_die.Append(ConstString(mangled).AsCString(), die.GetOffset());
		if (mangled.GetMangledName())
		full_name_to_function_die.Append(mangled.GetMangledName().AsCString(), die.GetOffset());
		if (mangled.GetDemangledName())
		full_name_to_function_die.Append(mangled.GetDemangledName().AsCString(), die.GetOffset());
		}
		break;

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