[llvm-exegesis] Add an analysis mode.

Summary:
The analysis mode gives the user a clustered view of the measurement results.
Next steps are (requires the split ok AsmTemplate.Name into {mnemonic, mode}):
 - Show the sched class.
 - Highlight any inconsistencies with the checked-in data.

Reviewers: gchatelet

Subscribers: mgorny, llvm-commits, tschuett

Differential Revision: https://reviews.llvm.org/D46865

llvm-svn: 332344

1 files changed, 67 insertions, 18 deletions

diff --git a/llvm/tools/llvm-exegesis/llvm-exegesis.cpp b/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
index 77683572da6..fff18776eec 100644
--- a/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
+++ b/llvm/tools/llvm-exegesis/llvm-exegesis.cpp
@@ -12,8 +12,10 @@
 ///
 //===----------------------------------------------------------------------===//
 
+#include "lib/Analysis.h"
 #include "lib/BenchmarkResult.h"
 #include "lib/BenchmarkRunner.h"
+#include "lib/Clustering.h"
 #include "lib/Latency.h"
 #include "lib/LlvmState.h"
 #include "lib/PerfHelper.h"
@@ -23,8 +25,11 @@
 #include "llvm/ADT/Twine.h"
 #include "llvm/MC/MCInstBuilder.h"
 #include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Format.h"
 #include "llvm/Support/Path.h"
+#include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include <algorithm>
 #include <random>
@@ -39,26 +44,41 @@ static llvm::cl::opt<std::string>
     OpcodeName("opcode-name", llvm::cl::desc("opcode to measure, by name"),
                llvm::cl::init(""));
 
-enum class BenchmarkModeE { Latency, Uops };
-static llvm::cl::opt<BenchmarkModeE>
-    BenchmarkMode("benchmark-mode", llvm::cl::desc("the benchmark mode to run"),
-                  llvm::cl::values(clEnumValN(BenchmarkModeE::Latency,
-                                              "latency", "Instruction Latency"),
-                                   clEnumValN(BenchmarkModeE::Uops, "uops",
-                                              "Uop Decomposition")));
+static llvm::cl::opt<std::string>
+    BenchmarkFile("benchmarks-file", llvm::cl::desc(""), llvm::cl::init("-"));
+
+enum class BenchmarkModeE { Latency, Uops, Analysis };
+static llvm::cl::opt<BenchmarkModeE> BenchmarkMode(
+    "benchmark-mode", llvm::cl::desc("the benchmark mode to run"),
+    llvm::cl::values(
+        clEnumValN(BenchmarkModeE::Latency, "latency", "Instruction Latency"),
+        clEnumValN(BenchmarkModeE::Uops, "uops", "Uop Decomposition"),
+        clEnumValN(BenchmarkModeE::Analysis, "analysis", "Analysis")));
 
 static llvm::cl::opt<unsigned>
     NumRepetitions("num-repetitions",
                    llvm::cl::desc("number of time to repeat the asm snippet"),
                    llvm::cl::init(10000));
 
+static llvm::cl::opt<unsigned> AnalysisNumPoints(
+    "analysis-numpoints",
+    llvm::cl::desc("minimum number of points in an analysis cluster"),
+    llvm::cl::init(3));
+
+static llvm::cl::opt<float>
+    AnalysisEpsilon("analysis-epsilon",
+                    llvm::cl::desc("dbscan epsilon for analysis clustering"),
+                    llvm::cl::init(0.1));
+
 namespace exegesis {
 
-void main() {
-  if (OpcodeName.empty() == (OpcodeIndex == 0)) {
+void benchmarkMain() {
+  if (exegesis::pfm::pfmInitialize())
+    llvm::report_fatal_error("cannot initialize libpfm");
+
+  if (OpcodeName.empty() == (OpcodeIndex == 0))
     llvm::report_fatal_error(
         "please provide one and only one of 'opcode-index' or 'opcode-name'");
-  }
 
   llvm::InitializeNativeTarget();
   llvm::InitializeNativeTargetAsmPrinter();
@@ -94,10 +114,42 @@ void main() {
   case BenchmarkModeE::Uops:
     Runner = llvm::make_unique<UopsBenchmarkRunner>();
     break;
+  case BenchmarkModeE::Analysis:
+    llvm_unreachable("not a benchmark");
   }
 
   Runner->run(State, Opcode, NumRepetitions > 0 ? NumRepetitions : 1, Filter)
-      .writeYamlOrDie("-");
+      .writeYamlOrDie(BenchmarkFile);
+  exegesis::pfm::pfmTerminate();
+}
+
+void analysisMain() {
+  // Read benchmarks.
+  const std::vector<InstructionBenchmark> Points =
+      InstructionBenchmark::readYamlsOrDie(BenchmarkFile);
+  llvm::outs() << "Parsed " << Points.size() << " benchmark points\n";
+  if (Points.empty()) {
+    llvm::errs() << "no benchmarks to analyze\n";
+    return;
+  }
+  // FIXME: Check that all points have the same triple/cpu.
+  // FIXME: Merge points from several runs (latency and uops).
+
+  llvm::InitializeAllTargets();
+  std::string Error;
+  const auto *TheTarget =
+      llvm::TargetRegistry::lookupTarget(Points[0].LLVMTriple, Error);
+  if (!TheTarget) {
+    llvm::errs() << "unknown target '" << Points[0].LLVMTriple << "'\n";
+    return;
+  }
+  std::unique_ptr<llvm::MCSubtargetInfo> STI(TheTarget->createMCSubtargetInfo(
+      Points[0].LLVMTriple, Points[0].CpuName, ""));
+
+  const auto Clustering = llvm::cantFail(InstructionBenchmarkClustering::create(
+      Points, AnalysisNumPoints, AnalysisEpsilon));
+  if (auto Err = printAnalysisClusters(Clustering, *STI, llvm::outs()))
+    llvm::report_fatal_error(std::move(Err));
 }
 
 } // namespace exegesis
@@ -105,13 +157,10 @@ void main() {
 int main(int Argc, char **Argv) {
   llvm::cl::ParseCommandLineOptions(Argc, Argv, "");
 
-  if (exegesis::pfm::pfmInitialize()) {
-    llvm::errs() << "cannot initialize libpfm\n";
-    return EXIT_FAILURE;
+  if (BenchmarkMode == BenchmarkModeE::Analysis) {
+    exegesis::analysisMain();
+  } else {
+    exegesis::benchmarkMain();
   }
-
-  exegesis::main();
-
-  exegesis::pfm::pfmTerminate();
   return EXIT_SUCCESS;
 }