[llvm-exegesis] Make createCounter a virtual method on Target to allow targets to create target-specific counters

[oontvoo]

Summary

Context: Split off from https://reviews.llvm.org/D77422

[oontvoo]

fix accidentally mixed-up branches

P.S: actually still not fixed. i've sorted out the branches locally and re-run arc diff but that didn't seem to fix it. Any idea which else to try?

[courbet]

Can you also include making the Counter virtual, and the use of this new function in FunctionExecutorImpl::runAndMeasure ? This would remove more unrelated changes from the other patch.

[oontvoo]

Move non-LBR related changes from benchmarkrunner and PerfHelper over too.

[oontvoo]

Sync/rebase

[courbet]

LGTM modulo one comment.

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

85 ↗

(On Diff #266683)

I don't think this needs to be virtual, does it ? readOrError is the real thing.

[oontvoo]

Make read() non-virtual

[oontvoo]

Committed (cc8fafa2be8d5315cc55aec54b2a6d7e60f470c4)

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

 #include "LlvmState.h"
 #include "SnippetGenerator.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/CodeGen/TargetPassConfig.h"
 #include "llvm/IR/CallingConv.h"
 #include "llvm/IR/LegacyPassManager.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/Support/Error.h"
 
 namespace llvm {
 namespace exegesis {
 
 struct PfmCountersInfo {
   // An optional name of a performance counter that can be used to measure
   // cycles.
   const char *CycleCounter;
struct CpuAndPfmCounters {
   bool operator<(StringRef S) const { return StringRef(CpuName) < S; }
 };
 
 class ExegesisTarget {
 public:
   explicit ExegesisTarget(ArrayRef<CpuAndPfmCounters> CpuPfmCounters)
       : CpuPfmCounters(CpuPfmCounters) {}
 
+  // Targets can use this to create target-specific perf counters.
+  virtual Expected<std::unique_ptr<pfm::Counter>>
+  createCounter(const char *CounterName, const LLVMState &State) const;
+
   // Targets can use this to add target-specific passes in assembleToStream();
   virtual void addTargetSpecificPasses(PassManagerBase &PM) const {}
 
   // Generates code to move a constant into a the given register.
   // Precondition: Value must fit into Reg.
   virtual std::vector<MCInst> setRegTo(const MCSubtargetInfo &STI, unsigned Reg,
                                        const APInt &Value) const = 0;
 

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

 //===-- Target.cpp ----------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 #include "Target.h"
 
 #include "LatencyBenchmarkRunner.h"
 #include "ParallelSnippetGenerator.h"
 #include "SerialSnippetGenerator.h"
 #include "UopsBenchmarkRunner.h"
+#include "llvm/ADT/Twine.h"
+#include "llvm/Support/Error.h"
 
 namespace llvm {
 namespace exegesis {
 
 ExegesisTarget::~ExegesisTarget() {} // anchor.
 
 static ExegesisTarget *FirstTarget = nullptr;
 
 const ExegesisTarget *ExegesisTarget::lookup(Triple TT) {
   for (const ExegesisTarget *T = FirstTarget; T != nullptr; T = T->Next) {
     if (T->matchesArch(TT.getArch()))
       return T;
   }
   return nullptr;
 }
 
+Expected<std::unique_ptr<pfm::Counter>>
+ExegesisTarget::createCounter(const char *CounterName,
+                              const LLVMState &) const {
+  pfm::PerfEvent Event(CounterName);
+  if (!Event.valid())
+    return llvm::make_error<Failure>(
+        llvm::Twine("Unable to create counter with name '")
+            .concat(CounterName)
+            .concat("'"));
+
+  return std::make_unique<pfm::Counter>(std::move(Event));
+}
+
 void ExegesisTarget::registerTarget(ExegesisTarget *Target) {
   if (FirstTarget == nullptr) {
     FirstTarget = Target;
     return;
   }
   if (Target->Next != nullptr)
     return; // Already registered.
   Target->Next = FirstTarget;