JIT: Don't always look up symbols for blocks

With tons of symbols, this results in noticeable stuttering, so
skip lookups if the perf dir option isn't set anyway.

Source/Core/Common/JitRegister.cpp

@@ -37,10 +37,13 @@ static File::IOFile s_perf_map_file;
 
 namespace JitRegister
 {
+static bool s_is_enabled = false;
+
 void Init(const std::string& perf_dir)
 {
 #if defined USE_OPROFILE && USE_OPROFILE
   s_agent = op_open_agent();
+  s_is_enabled = true;
 #endif
 
   if (!perf_dir.empty() || getenv("PERF_BUILDID_DIR"))
@@ -51,6 +54,7 @@ void Init(const std::string& perf_dir)
     // Disable buffering in order to avoid missing some mappings
     // if the event of a crash:
     std::setvbuf(s_perf_map_file.GetHandle(), nullptr, _IONBF, 0);
+    s_is_enabled = true;
   }
 }
 
@@ -67,6 +71,13 @@ void Shutdown()
 
   if (s_perf_map_file.IsOpen())
     s_perf_map_file.Close();
+
+  s_is_enabled = false;
+}
+
+bool IsEnabled()
+{
+  return s_is_enabled;
 }
 
 void RegisterV(const void* base_address, u32 code_size, const char* format, va_list args)

Source/Core/Common/JitRegister.h

@@ -12,6 +12,7 @@ namespace JitRegister
 void Init(const std::string& perf_dir);
 void Shutdown();
 void RegisterV(const void* base_address, u32 code_size, const char* format, va_list args);
+bool IsEnabled();
 
 inline void Register(const void* base_address, u32 code_size, const char* format, ...)
 {

Source/Core/Core/PowerPC/JitCommon/JitCache.cpp

@@ -132,12 +132,18 @@ void JitBaseBlockCache::FinalizeBlock(JitBlock& block, bool block_link,
     LinkBlock(block);
   }
 
-  if (Symbol* symbol = g_symbolDB.GetSymbolFromAddr(block.effectiveAddress))
+  Symbol* symbol = nullptr;
+  if (JitRegister::IsEnabled() &&
+      (symbol = g_symbolDB.GetSymbolFromAddr(block.effectiveAddress)) != nullptr)
+  {
     JitRegister::Register(block.checkedEntry, block.codeSize, "JIT_PPC_%s_%08x",
                           symbol->function_name.c_str(), block.physicalAddress);
+  }
   else
+  {
     JitRegister::Register(block.checkedEntry, block.codeSize, "JIT_PPC_%08x",
                           block.physicalAddress);
+  }
 }
 
 JitBlock* JitBaseBlockCache::GetBlockFromStartAddress(u32 addr, u32 msr)