[llvm] [llvm-profgen] Support creating profiles of arbitrary events (PR #99026)

[via llvm-commits]

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@@ -575,14 +591,54 @@ bool PerfScriptReader::extractLBRStack(TraceStream &TraceIt,
 
   // Skip the leading instruction pointer.
   size_t Index = 0;
+
+  StringRef EventName;
+  // Skip a perf event name. This may or may not exist.
+  if (Records.size() > Index && Records[Index].ends_with(":")) {
+    EventName = Records[Index].ltrim().rtrim(':');
+    Index++;
+
+    if (PerfEventFilter.empty()) {
+      WithColor::warning() << "No --perf-event filter was specified, but an "
+                              "\"event\" field was found in line "
+                           << TraceIt.getLineNumber() << ": "
+                           << TraceIt.getCurrentLine() << "\n";
+    } else if (std::find(PerfEventFilter.begin(), PerfEventFilter.end(),
+                         EventName) == PerfEventFilter.end()) {
+      TraceIt.advance();
+      return false;
+    }
+
+  } else if (!PerfEventFilter.empty()) {
+    WithColor::warning() << "A --perf-event filter was specified, but no "
+                            "\"event\" field found in line "
+                         << TraceIt.getLineNumber() << ": "
+                         << TraceIt.getCurrentLine() << "\n";
+  }
+
   uint64_t LeadingAddr;
-  if (!Records.empty() && !Records[0].contains('/')) {
-    if (Records[0].getAsInteger(16, LeadingAddr)) {
+  if (Records.size() > Index && !Records[Index].contains('/')) {
+    if (Records[Index].getAsInteger(16, LeadingAddr)) {
       WarnInvalidLBR(TraceIt);
       TraceIt.advance();
       return false;
     }
-    Index = 1;
+    Index++;
+  }
+
+  // We assume that if we saw an event name we also saw a leading addr.
+  // In other words, LeadingAddr is set if Index is 1 or 2.
+  if (LeadingIPOnly && Index > 0) {
+    // Form a profile only from the sample IP. Do not assume an LBR stack
+    // follows, and ignore it if it does.
+    uint64_t SampleIP = Binary->canonicalizeVirtualAddress(LeadingAddr);
+    bool SampleIPIsInternal = Binary->addressIsCode(SampleIP);
+    if (SampleIPIsInternal) {
+      // Form a half LBR entry where the sample IP is the destination.
+      LBRStack.emplace_back(LBREntry(SampleIP, SampleIP));
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WenleiHe wrote:

This doesn't really fit in LBRStack, instead, it fits CallStack better. All of the special case from `warnInvalidRange` can be avoided if we handle these events as part of `extractCallstack`. 

https://github.com/llvm/llvm-project/pull/99026