[llvm-exegesis] Add tablegen support for validation counters (llvm#76652)

This patch adds support in the llvm-exegesis tablegen emitter for
validation counters. Full support for validation counters in
llvm-exegesis will be added in a future patch.

Author: boomanaiden154

llvm/include/llvm/Target/TargetPfmCounters.td

@@ -28,6 +28,27 @@ class PfmIssueCounter<string resource_name, string counter>
   string ResourceName = resource_name;
 }
 
+// Definition of a validation event. A validation event represents a specific
+// event that can be measured using performance counters that is interesting
+// in regard to the snippet state.
+class ValidationEvent <int event_number> {
+  int EventNumber = event_number;
+}
+
+def L1DCacheLoadMiss    : ValidationEvent<0>;
+def InstructionRetired  : ValidationEvent<1>;
+def DataTLBLoadMiss     : ValidationEvent<2>;
+def DataTLBStoreMiss    : ValidationEvent<3>;
+
+// PfmValidationCounter provides a mapping between the events that are
+// are interesting in regards to the snippet execution environment and
+// a concrete performance counter name that can be looked up in libpfm.
+class PfmValidationCounter<ValidationEvent event_type, string counter>
+    : PfmCounter<counter> {
+  // The name of the event that the validation counter detects.
+  ValidationEvent EventType = event_type;
+}
+
 def NoPfmCounter : PfmCounter <""> {}
 
 // Set of PfmCounters for measuring sched model characteristics.
@@ -38,6 +59,9 @@ class ProcPfmCounters {
   PfmCounter UopsCounter = NoPfmCounter;
   // Processors can define how to measure issued uops by defining IssueCounters.
   list<PfmIssueCounter> IssueCounters = [];
+  // Processor can list mappings between validation events and real counters
+  // to measure the specified events.
+  list<PfmValidationCounter> ValidationCounters = [];
 }
 
 // A binding of a set of counters to a CPU.

llvm/lib/Target/X86/X86PfmCounters.td

@@ -275,6 +275,9 @@ def ZnVer2PfmCounters : ProcPfmCounters {
     PfmIssueCounter<"Zn2AGU", "ls_dispatch:ld_st_dispatch + ls_dispatch:ld_dispatch + ls_dispatch:store_dispatch">,
     PfmIssueCounter<"Zn2Divider", "div_op_count">
   ];
+  let ValidationCounters = [
+    PfmValidationCounter<InstructionRetired, "RETIRED_INSTRUCTIONS">
+  ];
 }
 def : PfmCountersBinding<"znver2", ZnVer2PfmCounters>;
 
@@ -288,6 +291,9 @@ def ZnVer3PfmCounters : ProcPfmCounters {
     PfmIssueCounter<"Zn3Store", "ls_dispatch:store_dispatch">,
     PfmIssueCounter<"Zn3Divider", "div_op_count">
   ];
+  let ValidationCounters = [
+    PfmValidationCounter<InstructionRetired, "RETIRED_INSTRUCTIONS">
+  ];
 }
 def : PfmCountersBinding<"znver3", ZnVer3PfmCounters>;
 

llvm/tools/llvm-exegesis/lib/Target.cpp

@@ -149,10 +149,15 @@ std::unique_ptr<BenchmarkRunner> ExegesisTarget::createUopsBenchmarkRunner(
 
 static_assert(std::is_trivial_v<PfmCountersInfo>,
               "We shouldn't have dynamic initialization here");
+
 const PfmCountersInfo PfmCountersInfo::Default = {nullptr, nullptr, nullptr,
-                                                  0u};
+                                                  0u,      nullptr, 0u};
 const PfmCountersInfo PfmCountersInfo::Dummy = {
-    pfm::PerfEvent::DummyEventString, pfm::PerfEvent::DummyEventString, nullptr,
+    pfm::PerfEvent::DummyEventString,
+    pfm::PerfEvent::DummyEventString,
+    nullptr,
+    0u,
+    nullptr,
     0u};
 
 const PfmCountersInfo &ExegesisTarget::getPfmCounters(StringRef CpuName) const {

llvm/tools/llvm-exegesis/lib/Target.h

@@ -39,6 +39,13 @@ extern cl::OptionCategory Options;
 extern cl::OptionCategory BenchmarkOptions;
 extern cl::OptionCategory AnalysisOptions;
 
+enum ValidationEvent {
+  L1DCacheLoadMiss,
+  InstructionRetired,
+  DataTLBLoadMiss,
+  DataTLBStoreMiss
+};
+
 struct PfmCountersInfo {
   // An optional name of a performance counter that can be used to measure
   // cycles.
@@ -59,6 +66,9 @@ struct PfmCountersInfo {
   const IssueCounter *IssueCounters;
   unsigned NumIssueCounters;
 
+  const std::pair<ValidationEvent, const char *> *ValidationEvents;
+  unsigned NumValidationEvents;
+
   static const PfmCountersInfo Default;
   static const PfmCountersInfo Dummy;
 };

llvm/utils/TableGen/ExegesisEmitter.cpp

@@ -81,6 +81,11 @@ collectPfmCounters(const RecordKeeper &Records) {
                         "duplicate ResourceName " + ResourceName);
       AddPfmCounterName(IssueCounter);
     }
+
+    for (const Record *ValidationCounter :
+         Def->getValueAsListOfDefs("ValidationCounters"))
+      AddPfmCounterName(ValidationCounter);
+
     AddPfmCounterName(Def->getValueAsDef("CycleCounter"));
     AddPfmCounterName(Def->getValueAsDef("UopsCounter"));
   }
@@ -100,6 +105,17 @@ ExegesisEmitter::ExegesisEmitter(RecordKeeper &RK)
   Target = std::string(Targets[0]->getName());
 }
 
+struct ValidationCounterInfo {
+  int64_t EventNumber;
+  StringRef EventName;
+  unsigned PfmCounterID;
+};
+
+bool EventNumberLess(const ValidationCounterInfo &LHS,
+                     const ValidationCounterInfo &RHS) {
+  return LHS.EventNumber < RHS.EventNumber;
+}
+
 void ExegesisEmitter::emitPfmCountersInfo(const Record &Def,
                                           unsigned &IssueCountersTableOffset,
                                           raw_ostream &OS) const {
@@ -109,6 +125,31 @@ void ExegesisEmitter::emitPfmCountersInfo(const Record &Def,
       Def.getValueAsDef("UopsCounter")->getValueAsString("Counter");
   const size_t NumIssueCounters =
       Def.getValueAsListOfDefs("IssueCounters").size();
+  const size_t NumValidationCounters =
+      Def.getValueAsListOfDefs("ValidationCounters").size();
+
+  // Emit Validation Counters Array
+  if (NumValidationCounters != 0) {
+    std::vector<ValidationCounterInfo> ValidationCounters;
+    ValidationCounters.reserve(NumValidationCounters);
+    for (const Record *ValidationCounter :
+         Def.getValueAsListOfDefs("ValidationCounters")) {
+      ValidationCounters.push_back(
+          {ValidationCounter->getValueAsDef("EventType")
+               ->getValueAsInt("EventNumber"),
+           ValidationCounter->getValueAsDef("EventType")->getName(),
+           getPfmCounterId(ValidationCounter->getValueAsString("Counter"))});
+    }
+    std::sort(ValidationCounters.begin(), ValidationCounters.end(),
+              EventNumberLess);
+    OS << "\nstatic const std::pair<ValidationEvent, const char*> " << Target
+       << Def.getName() << "ValidationCounters[] = {\n";
+    for (const ValidationCounterInfo &VCI : ValidationCounters) {
+      OS << "  { " << VCI.EventName << ", " << Target << "PfmCounterNames["
+         << VCI.PfmCounterID << "]},\n";
+    }
+    OS << "};\n";
+  }
 
   OS << "\nstatic const PfmCountersInfo " << Target << Def.getName()
      << " = {\n";
@@ -129,10 +170,17 @@ void ExegesisEmitter::emitPfmCountersInfo(const Record &Def,
 
   // Issue Counters
   if (NumIssueCounters == 0)
-    OS << "  nullptr,  // No issue counters.\n  0\n";
+    OS << "  nullptr, 0, // No issue counters\n";
   else
     OS << "  " << Target << "PfmIssueCounters + " << IssueCountersTableOffset
-       << ", " << NumIssueCounters << " // Issue counters.\n";
+       << ", " << NumIssueCounters << ", // Issue counters.\n";
+
+  // Validation Counters
+  if (NumValidationCounters == 0)
+    OS << "  nullptr, 0 // No validation counters.\n";
+  else
+    OS << "  " << Target << Def.getName() << "ValidationCounters, "
+       << NumValidationCounters << " // Validation counters.\n";
 
   OS << "};\n";
   IssueCountersTableOffset += NumIssueCounters;