[llvm-exegesis][NFC] Add a way to declare the default counter binding for unbound CPUs for a target.

Summary:
This simplifies the code and moves everything to tablegen for consistency. This
also prepares the ground for adding issue counters.

Reviewers: gchatelet, john.brawn, jsji

Subscribers: nemanjai, mgorny, javed.absar, kbarton, tschuett, llvm-commits

Differential Revision: https://reviews.llvm.org/D54297

llvm-svn: 346489

llvm/include/llvm/Target/TargetPfmCounters.td

@@ -44,3 +44,7 @@ class PfmCountersBinding<string cpu_name, ProcPfmCounters counters> {
   string CpuName = cpu_name;
   ProcPfmCounters Counters = counters;
 }
+
+// Declares the default binding for unbound CPUs for the target.
+class PfmCountersDefaultBinding<ProcPfmCounters counters>
+    : PfmCountersBinding<"", counters> {}

llvm/lib/Target/AArch64/AArch64.td

@@ -626,3 +626,9 @@ def AArch64 : Target {
   let AssemblyWriters = [GenericAsmWriter, AppleAsmWriter];
   let AllowRegisterRenaming = 1;
 }
+
+//===----------------------------------------------------------------------===//
+// Pfm Counters
+//===----------------------------------------------------------------------===//
+
+include "AArch64PfmCounters.td"

llvm/lib/Target/AArch64/AArch64PfmCounters.td

@@ -0,0 +1,19 @@
+//===-- AArch64PfmCounters.td - AArch64 Hardware Counters --*- tablegen -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This describes the available hardware counters for AArch64.
+//
+//===----------------------------------------------------------------------===//
+
+def CpuCyclesPfmCounter : PfmCounter<"CPU_CYCLES">;
+
+def DefaultPfmCounters : ProcPfmCounters {
+  let CycleCounter = CpuCyclesPfmCounter;
+}
+def : PfmCountersDefaultBinding<DefaultPfmCounters>;

llvm/lib/Target/AArch64/CMakeLists.txt

@@ -15,6 +15,7 @@ tablegen(LLVM AArch64GenRegisterBank.inc -gen-register-bank)
 tablegen(LLVM AArch64GenRegisterInfo.inc -gen-register-info)
 tablegen(LLVM AArch64GenSubtargetInfo.inc -gen-subtarget)
 tablegen(LLVM AArch64GenSystemOperands.inc -gen-searchable-tables)
+tablegen(LLVM AArch64GenExegesis.inc -gen-exegesis)
 
 add_public_tablegen_target(AArch64CommonTableGen)
 

llvm/lib/Target/PowerPC/CMakeLists.txt

@@ -10,6 +10,7 @@ tablegen(LLVM PPCGenInstrInfo.inc -gen-instr-info)
 tablegen(LLVM PPCGenMCCodeEmitter.inc -gen-emitter)
 tablegen(LLVM PPCGenRegisterInfo.inc -gen-register-info)
 tablegen(LLVM PPCGenSubtargetInfo.inc -gen-subtarget)
+tablegen(LLVM PPCGenExegesis.inc -gen-exegesis)
 
 add_public_tablegen_target(PowerPCCommonTableGen)
 

llvm/lib/Target/PowerPC/PPC.td

@@ -478,3 +478,9 @@ def PPC : Target {
   let AssemblyParserVariants = [PPCAsmParserVariant];
   let AllowRegisterRenaming = 1;
 }
+
+//===----------------------------------------------------------------------===//
+// Pfm Counters
+//===----------------------------------------------------------------------===//
+
+include "PPCPfmCounters.td"

llvm/lib/Target/PowerPC/PPCPfmCounters.td

@@ -0,0 +1,19 @@
+//===-- PPCPfmCounters.td - PPC Hardware Counters ----------*- tablegen -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This describes the available hardware counters for PPC.
+//
+//===----------------------------------------------------------------------===//
+
+def CpuCyclesPfmCounter : PfmCounter<"CYCLES">;
+
+def DefaultPfmCounters : ProcPfmCounters {
+  let CycleCounter = CpuCyclesPfmCounter;
+}
+def : PfmCountersDefaultBinding<DefaultPfmCounters>;

llvm/lib/Target/X86/X86PfmCounters.td

@@ -14,6 +14,10 @@
 def UnhaltedCoreCyclesPfmCounter : PfmCounter<"unhalted_core_cycles">;
 def UopsIssuedPfmCounter : PfmCounter<"uops_issued:any">;
 
+// No default counters on X86.
+def DefaultPfmCounters : ProcPfmCounters {}
+def : PfmCountersDefaultBinding<DefaultPfmCounters>;
+
 def SandyBridgePfmCounters : ProcPfmCounters {
   let CycleCounter = UnhaltedCoreCyclesPfmCounter;
   let UopsCounter = UopsIssuedPfmCounter;

llvm/tools/llvm-exegesis/lib/AArch64/Target.cpp

@@ -14,22 +14,6 @@
 namespace llvm {
 namespace exegesis {
 
-namespace {
-
-class AArch64LatencyBenchmarkRunner : public LatencyBenchmarkRunner {
-public:
-  AArch64LatencyBenchmarkRunner(const LLVMState &State)
-      : LatencyBenchmarkRunner(State) {}
-
-private:
-  const char *getCounterName() const override {
-    // All AArch64 subtargets have CPU_CYCLES as the cycle counter name
-    return "CPU_CYCLES";
-  }
-};
-
-namespace {
-
 static unsigned getLoadImmediateOpcode(unsigned RegBitWidth) {
   switch (RegBitWidth) {
   case 32:
@@ -50,11 +34,13 @@ static llvm::MCInst loadImmediate(unsigned Reg, unsigned RegBitWidth,
       .addImm(Value.getZExtValue());
 }
 
-} // namespace
+#include "AArch64GenExegesis.inc"
+
+namespace {
 
 class ExegesisAArch64Target : public ExegesisTarget {
 public:
-  ExegesisAArch64Target() : ExegesisTarget({}) {}
+  ExegesisAArch64Target() : ExegesisTarget(AArch64CpuPfmCounters) {}
 
 private:
   std::vector<llvm::MCInst> setRegTo(const llvm::MCSubtargetInfo &STI,
@@ -76,11 +62,6 @@ private:
     // Function return is a pseudo-instruction that needs to be expanded
     PM.add(llvm::createAArch64ExpandPseudoPass());
   }
-
-  std::unique_ptr<BenchmarkRunner>
-  createLatencyBenchmarkRunner(const LLVMState &State) const override {
-    return llvm::make_unique<AArch64LatencyBenchmarkRunner>(State);
-  }
 };
 
 } // namespace

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

@@ -166,13 +166,6 @@ LatencySnippetGenerator::generateCodeTemplates(const Instruction &Instr) const {
   return std::move(Results);
 }
 
-const char *LatencyBenchmarkRunner::getCounterName() const {
-  const char *CounterName = State.getPfmCounters().CycleCounter;
-  if (!CounterName)
-    llvm::report_fatal_error("sched model does not define a cycle counter");
-  return CounterName;
-}
-
 LatencyBenchmarkRunner::~LatencyBenchmarkRunner() = default;
 
 llvm::Expected<std::vector<BenchmarkMeasure>>
@@ -182,9 +175,9 @@ LatencyBenchmarkRunner::runMeasurements(
   // measure several times and take the minimum value.
   constexpr const int NumMeasurements = 30;
   int64_t MinValue = std::numeric_limits<int64_t>::max();
-  const char *CounterName = getCounterName();
+  const char *CounterName = State.getPfmCounters().CycleCounter;
   if (!CounterName)
-    llvm::report_fatal_error("could not determine cycle counter name");
+    llvm::report_fatal_error("sched model does not define a cycle counter");
   for (size_t I = 0; I < NumMeasurements; ++I) {
     auto ExpectedCounterValue = Executor.runAndMeasure(CounterName);
     if (!ExpectedCounterValue)

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

@@ -40,8 +40,6 @@ public:
 private:
   llvm::Expected<std::vector<BenchmarkMeasure>>
   runMeasurements(const FunctionExecutor &Executor) const override;
-
-  virtual const char *getCounterName() const;
 };
 } // namespace exegesis
 } // namespace llvm

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

@@ -15,24 +15,12 @@
 namespace llvm {
 namespace exegesis {
 
-namespace {
-class PowerPCLatencyBenchmarkRunner : public LatencyBenchmarkRunner {
-public:
-  PowerPCLatencyBenchmarkRunner(const LLVMState &State)
-      : LatencyBenchmarkRunner(State) {}
-
-private:
-  const char *getCounterName() const override {
-    // All PowerPC subtargets have CYCLES as the cycle counter name
-    return "CYCLES";
-  }
-};
-} // end anonymous namespace
+#include "PPCGenExegesis.inc"
 
 namespace {
 class ExegesisPowerPCTarget : public ExegesisTarget {
 public:
-  ExegesisPowerPCTarget() : ExegesisTarget({}) {}
+  ExegesisPowerPCTarget() : ExegesisTarget(PPCCpuPfmCounters) {}
 
 private:
   std::vector<llvm::MCInst> setRegTo(const llvm::MCSubtargetInfo &STI,
@@ -41,10 +29,6 @@ private:
   bool matchesArch(llvm::Triple::ArchType Arch) const override {
     return Arch == llvm::Triple::ppc64le;
   }
-  std::unique_ptr<BenchmarkRunner>
-  createLatencyBenchmarkRunner(const LLVMState &State) const override {
-    return llvm::make_unique<PowerPCLatencyBenchmarkRunner>(State);
-  }
 };
 } // end anonymous namespace
 

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

@@ -87,7 +87,8 @@ ExegesisTarget::createUopsBenchmarkRunner(const LLVMState &State) const {
 
 static_assert(std::is_pod<PfmCountersInfo>::value,
               "We shouldn't have dynamic initialization here");
-const PfmCountersInfo PfmCountersInfo::Default = {nullptr, nullptr, nullptr, 0u};
+const PfmCountersInfo PfmCountersInfo::Default = {nullptr, nullptr, nullptr,
+                                                  0u};
 
 const PfmCountersInfo &
 ExegesisTarget::getPfmCounters(llvm::StringRef CpuName) const {
@@ -103,7 +104,13 @@ ExegesisTarget::getPfmCounters(llvm::StringRef CpuName) const {
       std::lower_bound(CpuPfmCounters.begin(), CpuPfmCounters.end(), CpuName);
   if (Found == CpuPfmCounters.end() ||
       llvm::StringRef(Found->CpuName) != CpuName) {
-    return PfmCountersInfo::Default;
+    // Use the default.
+    if (CpuPfmCounters.begin() != CpuPfmCounters.end() &&
+        CpuPfmCounters.begin()->CpuName[0] == '\0') {
+      Found = CpuPfmCounters.begin(); // The target specifies a default.
+    } else {
+      return PfmCountersInfo::Default; // No default for the target.
+    }
   }
   assert(Found->PCI && "Missing counters");
   return *Found->PCI;

llvm/unittests/tools/llvm-exegesis/AArch64/TargetTest.cpp

@@ -59,6 +59,12 @@ TEST_F(AArch64TargetTest, SetRegToConstant) {
   EXPECT_THAT(Insts, Not(IsEmpty()));
 }
 
+TEST_F(AArch64TargetTest, DefaultPfmCounters) {
+  EXPECT_EQ(ExegesisTarget_->getPfmCounters("").CycleCounter, "CPU_CYCLES");
+  EXPECT_EQ(ExegesisTarget_->getPfmCounters("unknown_cpu").CycleCounter,
+            "CPU_CYCLES");
+}
+
 } // namespace
 } // namespace exegesis
 } // namespace llvm

llvm/unittests/tools/llvm-exegesis/PowerPC/TargetTest.cpp

@@ -59,6 +59,12 @@ TEST_F(PowerPCTargetTest, SetRegToConstant) {
   EXPECT_THAT(Insts, Not(IsEmpty()));
 }
 
+TEST_F(PowerPCTargetTest, DefaultPfmCounters) {
+  EXPECT_EQ(ExegesisTarget_->getPfmCounters("").CycleCounter, "CYCLES");
+  EXPECT_EQ(ExegesisTarget_->getPfmCounters("unknown_cpu").CycleCounter,
+            "CYCLES");
+}
+
 } // namespace
 } // namespace exegesis
 } // namespace llvm

llvm/utils/TableGen/ExegesisEmitter.cpp

@@ -11,6 +11,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/Support/Debug.h"
@@ -114,10 +115,6 @@ void ExegesisEmitter::emitPfmCountersInfo(const Record &Def,
   const size_t NumIssueCounters =
       Def.getValueAsListOfDefs("IssueCounters").size();
 
-  // This is the default, do not emit.
-  if (CycleCounter.empty() && UopsCounter.empty() && NumIssueCounters == 0)
-    return;
-
   OS << "\nstatic const PfmCountersInfo " << Target << Def.getName()
      << " = {\n";
 
@@ -157,28 +154,35 @@ void ExegesisEmitter::emitPfmCounters(raw_ostream &OS) const {
   // Emit the IssueCounters table.
   const auto PfmCounterDefs =
       Records.getAllDerivedDefinitions("ProcPfmCounters");
-  OS << "static const PfmCountersInfo::IssueCounter " << Target
-     << "PfmIssueCounters[] = {\n";
-  for (const Record *Def : PfmCounterDefs) {
-    for (const Record *ICDef : Def->getValueAsListOfDefs("IssueCounters"))
-      OS << "  { " << Target << "PfmCounterNames["
-         << getPfmCounterId(ICDef->getValueAsString("Counter")) << "], \""
-         << ICDef->getValueAsString("ResourceName") << "\"},\n";
+  // Only emit if non-empty.
+  const bool HasAtLeastOnePfmIssueCounter =
+      llvm::any_of(PfmCounterDefs, [](const Record *Def) {
+        return !Def->getValueAsListOfDefs("IssueCounters").empty();
+      });
+  if (HasAtLeastOnePfmIssueCounter) {
+    OS << "static const PfmCountersInfo::IssueCounter " << Target
+       << "PfmIssueCounters[] = {\n";
+    for (const Record *Def : PfmCounterDefs) {
+      for (const Record *ICDef : Def->getValueAsListOfDefs("IssueCounters"))
+        OS << "  { " << Target << "PfmCounterNames["
+           << getPfmCounterId(ICDef->getValueAsString("Counter")) << "], \""
+           << ICDef->getValueAsString("ResourceName") << "\"},\n";
+    }
+    OS << "};\n";
   }
 
-  OS << "};\n";
-
   // Now generate the PfmCountersInfo.
   unsigned IssueCountersTableOffset = 0;
   for (const Record *Def : PfmCounterDefs)
     emitPfmCountersInfo(*Def, IssueCountersTableOffset, OS);
 
   OS << "\n";
-}
+} // namespace
 
 void ExegesisEmitter::emitPfmCountersLookupTable(raw_ostream &OS) const {
   std::vector<Record *> Bindings =
       Records.getAllDerivedDefinitions("PfmCountersBinding");
+  assert(!Bindings.empty() && "there must be at least one binding");
   llvm::sort(Bindings, [](const Record *L, const Record *R) {
     return L->getValueAsString("CpuName") < R->getValueAsString("CpuName");
   });