[llvm] [BOLT][AArch64] Introduce SPE mode in BasicAggregation (PR #120741)

[Pavel Iliin via llvm-commits]

================
@@ -1703,6 +1786,46 @@ std::error_code DataAggregator::parseBasicEvents() {
   return std::error_code();
 }
 
+std::error_code DataAggregator::parseSpeAsBasicEvents() {
+  outs() << "PERF2BOLT: parsing SPE data as basic events (no LBR)...\n";
+  NamedRegionTimer T("parseSPEBasic", "Parsing SPE as basic events",
+                     TimerGroupName, TimerGroupDesc, opts::TimeAggregator);
+  uint64_t NumSpeBranchSamples = 0;
+
+  // Convert entries to one or two basic samples, depending on whether there is
+  // branch target information.
+  while (hasData()) {
+    auto SamplePair = parseSpeAsBasicSamples();
+    if (std::error_code EC = SamplePair.getError())
+      return EC;
+
+    auto registerSample = [this](const PerfBasicSample *Sample) {
+      if (!Sample->PC)
+        return;
+
+      if (BinaryFunction *BF = getBinaryFunctionContainingAddress(Sample->PC))
+        BF->setHasProfileAvailable();
+
+      ++BasicSamples[Sample->PC];
+      EventNames.insert(Sample->EventName);
+    };
+
+    if (SamplePair->first.PC != 0x0 && SamplePair->second.PC != 0x0)
+      ++NumSpeBranchSamples;
+
+    registerSample(&SamplePair->first);
+    registerSample(&SamplePair->second);
----------------
ilinpv wrote:

Right, thank you @paschalis-mpeis for clarifying about taken/not taken information and updating examples. @aaupov @maksfb would you like any additional explanations regarding SPE packets? Generally speaking SPE is providing event  based sampling for branches and doesn't have enough information to create trace of N>1 branches and inferring fall throughs. We are aiming to add BRBE ([Branch Record Buffer Extension](https://developer.arm.com/documentation/109697/2024_12/Feature-descriptions/The-Armv9-2-architecture-extension?lang=en )) support for this in BOLT and provide branch stack trace like LBR with it.

https://github.com/llvm/llvm-project/pull/120741