[llvm] [llvm-profgen][SPGO] Support profiles with multiple concurrent processes (PR #169353)

[via llvm-commits]

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@@ -541,22 +555,41 @@ void PerfScriptReader::updateBinaryAddress(const MMapEvent &Event) {
     return;
 
   // Drop the event if process does not match pid filter
-  if (PIDFilter && Event.PID != *PIDFilter)
+  if (!PIDFilter.empty() && !PIDFilter.contains(Event.PID))
     return;
 
+  // If no PID is in the profile's samples, we treat everything as the default
+  // PID value
+  int32_t LookupPID = MultiProcessProfile ? Event.PID : DefaultPID;
+
   // Drop the event if its image is loaded at the same address
-  if (Event.Address == Binary->getBaseAddress()) {
+  if (Event.Address == Binary->getBaseAddress(LookupPID)) {
     Binary->setIsLoadedByMMap(true);
     return;
   }
 
+  std::optional<int32_t> LastSeenPID = Binary->getLastSeenPID();
+  if (!MultiProcessProfile && LastSeenPID.has_value() &&
+      LastSeenPID.value() != Event.PID) {
+    WithColor::warning() << "Binary previously loaded in process ID "
+                         << LastSeenPID.value() << " at "
+                         << format("0x%" PRIx64,
+                                   Binary->getBaseAddress(LookupPID))
+                         << " was reloaded in process ID " << Event.PID
+                         << " at " << format("0x%" PRIx64, Event.Address)
+                         << ". If profiling multiple processes running "
+                         << "concurrently, use --multi-process-profile to "
+                         << "prevent loss of samples.\n";
+  }
+  Binary->setLastSeenPID(Event.PID);
+
   if (IsKernel || Event.Offset == Binary->getTextSegmentOffset()) {
     // A binary image could be unloaded and then reloaded at different
     // place, so update binary load address.
     // Only update for the first executable segment and assume all other
     // segments are loaded at consecutive memory addresses, which is the case on
     // X64.
-    Binary->setBaseAddress(Event.Address);
+    Binary->setBaseAddress(LookupPID, Event.Address);
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HighW4y2H3ll wrote:

This doesn’t seem to apply to kernel?

https://github.com/llvm/llvm-project/pull/169353