[XRay] cache symbolized function names for a repeatedly queried function ID

Summary:
Processing 2 GB XRay traces with "llvm-xray convert -symbolize" needs to
go over each trace record and symbolize the function name refered to by
its ID.  Currently this happens by asking the LLVM symbolizer code every
single time.  A simple cache can save around 30 minutes of processing of
that trace.

llvm-xray's resident memory usage increased negligibly with this cache.

Reviewers: dberris

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D43896

llvm-svn: 326407

1 files changed, 7 insertions, 1 deletions

diff --git a/llvm/tools/llvm-xray/func-id-helper.cc b/llvm/tools/llvm-xray/func-id-helper.cc
index 3234010695b..9bf55b23bdd 100644
--- a/llvm/tools/llvm-xray/func-id-helper.cc
+++ b/llvm/tools/llvm-xray/func-id-helper.cc
@@ -19,6 +19,10 @@ using namespace llvm;
 using namespace xray;
 
 std::string FuncIdConversionHelper::SymbolOrNumber(int32_t FuncId) const {
+  auto CacheIt = CachedNames.find(FuncId);
+  if (CacheIt != CachedNames.end())
+    return CacheIt->second;
+
   std::ostringstream F;
   auto It = FunctionAddresses.find(FuncId);
   if (It == FunctionAddresses.end()) {
@@ -37,7 +41,9 @@ std::string FuncIdConversionHelper::SymbolOrNumber(int32_t FuncId) const {
       F << "@(" << std::hex << It->second << ")";
     });
 
-  return F.str();
+  auto S = F.str();
+  CachedNames[FuncId] = S;
+  return S;
 }
 
 std::string FuncIdConversionHelper::FileLineAndColumn(int32_t FuncId) const {