[llvm] da4e5fc - [llvm-profgen] Deduplicate PID when processing perf input

[Wenlei He via llvm-commits]

Author: Wenlei He
Date: 2021-10-10T13:30:17-07:00
New Revision: da4e5fc86158c669ddcb335d151fffd7c6e2ed4b

URL: https://github.com/llvm/llvm-project/commit/da4e5fc86158c669ddcb335d151fffd7c6e2ed4b
DIFF: https://github.com/llvm/llvm-project/commit/da4e5fc86158c669ddcb335d151fffd7c6e2ed4b.diff

LOG: [llvm-profgen] Deduplicate PID when processing perf input

When parsing mmap to retrieve PID, deduplicate them before passing PID list to perf script. Perf script would error out when there's duplicated PID in the input, however raw perf data may main duplicated PID for large binary where more than one mmap is needed to load executable segment.

Differential Revision: https://reviews.llvm.org/D111384

Added: 
    

Modified: 
    llvm/tools/llvm-profgen/PerfReader.cpp

Removed: 
    


################################################################################
diff  --git a/llvm/tools/llvm-profgen/PerfReader.cpp b/llvm/tools/llvm-profgen/PerfReader.cpp
index 019ca5ab46512..2aa66832a051a 100644
--- a/llvm/tools/llvm-profgen/PerfReader.cpp
+++ b/llvm/tools/llvm-profgen/PerfReader.cpp
@@ -322,18 +322,26 @@ std::string PerfReaderBase::convertPerfDataToTrace(ProfiledBinary *Binary,
   // Collect the PIDs
   TraceStream TraceIt(PerfTraceFile);
   std::string PIDs;
+  std::unordered_set<uint32_t> PIDSet;
   while (!TraceIt.isAtEoF()) {
     MMapEvent MMap;
     if (isMMap2Event(TraceIt.getCurrentLine()) &&
         extractMMap2EventForBinary(Binary, TraceIt.getCurrentLine(), MMap)) {
-      if (!PIDs.empty()) {
-        PIDs.append(",");
+      auto It = PIDSet.emplace(MMap.PID);
+      if (It.second) {
+        if (!PIDs.empty()) {
+          PIDs.append(",");
+        }
+        PIDs.append(utostr(MMap.PID));
       }
-      PIDs.append(utostr(MMap.PID));
     }
     TraceIt.advance();
   }
 
+  if (PIDs.empty()) {
+    exitWithError("No relevant mmap event is found in perf data.");
+  }
+
   // Run perf script again to retrieve events for PIDs collected above
   StringRef ScriptSampleArgs[] = {PerfPath, "script",     "--show-mmap-events",
                                   "-F",     "ip,brstack", "--pid",