[ctx_prof] CtxProfAnalysis (#102084)

This is an immutable analysis that loads and makes the contextual profile available to other passes. This patch introduces the analysis and an analysis printer pass. Subsequent patches will introduce the APIs that IPO passes will call to modify the profile as result of their changes.

Author: mtrofin

llvm/include/llvm/Analysis/CtxProfAnalysis.h

@@ -0,0 +1,70 @@
+//===- CtxProfAnalysis.h - maintain contextual profile info   -*- 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
+//
+//===----------------------------------------------------------------------===//
+//
+#ifndef LLVM_ANALYSIS_CTXPROFANALYSIS_H
+#define LLVM_ANALYSIS_CTXPROFANALYSIS_H
+
+#include "llvm/IR/GlobalValue.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/ProfileData/PGOCtxProfReader.h"
+#include <map>
+
+namespace llvm {
+
+class CtxProfAnalysis;
+
+/// The instrumented contextual profile, produced by the CtxProfAnalysis.
+class PGOContextualProfile {
+  std::optional<PGOCtxProfContext::CallTargetMapTy> Profiles;
+
+public:
+  explicit PGOContextualProfile(PGOCtxProfContext::CallTargetMapTy &&Profiles)
+      : Profiles(std::move(Profiles)) {}
+  PGOContextualProfile() = default;
+  PGOContextualProfile(const PGOContextualProfile &) = delete;
+  PGOContextualProfile(PGOContextualProfile &&) = default;
+
+  operator bool() const { return Profiles.has_value(); }
+
+  const PGOCtxProfContext::CallTargetMapTy &profiles() const {
+    return *Profiles;
+  }
+
+  bool invalidate(Module &, const PreservedAnalyses &PA,
+                  ModuleAnalysisManager::Invalidator &) {
+    // Check whether the analysis has been explicitly invalidated. Otherwise,
+    // it's stateless and remains preserved.
+    auto PAC = PA.getChecker<CtxProfAnalysis>();
+    return !PAC.preservedWhenStateless();
+  }
+};
+
+class CtxProfAnalysis : public AnalysisInfoMixin<CtxProfAnalysis> {
+  StringRef Profile;
+
+public:
+  static AnalysisKey Key;
+  explicit CtxProfAnalysis(StringRef Profile) : Profile(Profile) {};
+
+  using Result = PGOContextualProfile;
+
+  PGOContextualProfile run(Module &M, ModuleAnalysisManager &MAM);
+};
+
+class CtxProfAnalysisPrinterPass
+    : public PassInfoMixin<CtxProfAnalysisPrinterPass> {
+  raw_ostream &OS;
+
+public:
+  explicit CtxProfAnalysisPrinterPass(raw_ostream &OS) : OS(OS) {}
+
+  PreservedAnalyses run(Module &M, ModuleAnalysisManager &MAM);
+  static bool isRequired() { return true; }
+};
+} // namespace llvm
+#endif // LLVM_ANALYSIS_CTXPROFANALYSIS_H

llvm/lib/Analysis/CMakeLists.txt

@@ -46,6 +46,7 @@ add_llvm_component_library(LLVMAnalysis
   CostModel.cpp
   CodeMetrics.cpp
   ConstantFolding.cpp
+  CtxProfAnalysis.cpp
   CycleAnalysis.cpp
   DDG.cpp
   DDGPrinter.cpp

llvm/lib/Analysis/CtxProfAnalysis.cpp

@@ -0,0 +1,95 @@
+//===- CtxProfAnalysis.cpp - contextual profile analysis ------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Implementation of the contextual profile analysis, which maintains contextual
+// profiling info through IPO passes.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/Analysis/CtxProfAnalysis.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/IR/Analysis.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/PassManager.h"
+#include "llvm/ProfileData/PGOCtxProfReader.h"
+#include "llvm/Support/JSON.h"
+#include "llvm/Support/MemoryBuffer.h"
+
+#define DEBUG_TYPE "ctx_prof"
+
+namespace llvm {
+namespace json {
+Value toJSON(const PGOCtxProfContext &P) {
+  Object Ret;
+  Ret["Guid"] = P.guid();
+  Ret["Counters"] = Array(P.counters());
+  if (P.callsites().empty())
+    return Ret;
+  auto AllCS =
+      ::llvm::map_range(P.callsites(), [](const auto &P) { return P.first; });
+  auto MaxIt = ::llvm::max_element(AllCS);
+  assert(MaxIt != AllCS.end() && "We should have a max value because the "
+                                 "callsites collection is not empty.");
+  Array CSites;
+  // Iterate to, and including, the maximum index.
+  for (auto I = 0U, Max = *MaxIt; I <= Max; ++I) {
+    CSites.push_back(Array());
+    Array &Targets = *CSites.back().getAsArray();
+    if (P.hasCallsite(I))
+      for (const auto &[_, Ctx] : P.callsite(I))
+        Targets.push_back(toJSON(Ctx));
+  }
+  Ret["Callsites"] = std::move(CSites);
+
+  return Ret;
+}
+
+Value toJSON(const PGOCtxProfContext::CallTargetMapTy &P) {
+  Array Ret;
+  for (const auto &[_, Ctx] : P)
+    Ret.push_back(toJSON(Ctx));
+  return Ret;
+}
+} // namespace json
+} // namespace llvm
+
+using namespace llvm;
+
+AnalysisKey CtxProfAnalysis::Key;
+
+CtxProfAnalysis::Result CtxProfAnalysis::run(Module &M,
+                                             ModuleAnalysisManager &MAM) {
+  ErrorOr<std::unique_ptr<MemoryBuffer>> MB = MemoryBuffer::getFile(Profile);
+  if (auto EC = MB.getError()) {
+    M.getContext().emitError("could not open contextual profile file: " +
+                             EC.message());
+    return {};
+  }
+  PGOCtxProfileReader Reader(MB.get()->getBuffer());
+  auto MaybeCtx = Reader.loadContexts();
+  if (!MaybeCtx) {
+    M.getContext().emitError("contextual profile file is invalid: " +
+                             toString(MaybeCtx.takeError()));
+    return {};
+  }
+  return Result(std::move(*MaybeCtx));
+}
+
+PreservedAnalyses CtxProfAnalysisPrinterPass::run(Module &M,
+                                                  ModuleAnalysisManager &MAM) {
+  CtxProfAnalysis::Result &C = MAM.getResult<CtxProfAnalysis>(M);
+  if (!C) {
+    M.getContext().emitError("Invalid CtxProfAnalysis");
+    return PreservedAnalyses::all();
+  }
+  const auto JSONed = ::llvm::json::toJSON(C.profiles());
+
+  OS << formatv("{0:2}", JSONed);
+  OS << "\n";
+  return PreservedAnalyses::all();
+}

llvm/lib/Passes/PassBuilder.cpp

@@ -28,6 +28,7 @@
 #include "llvm/Analysis/CallGraph.h"
 #include "llvm/Analysis/CallPrinter.h"
 #include "llvm/Analysis/CostModel.h"
+#include "llvm/Analysis/CtxProfAnalysis.h"
 #include "llvm/Analysis/CycleAnalysis.h"
 #include "llvm/Analysis/DDG.h"
 #include "llvm/Analysis/DDGPrinter.h"
@@ -330,6 +331,8 @@ cl::opt<bool> PrintPipelinePasses(
              "(best-effort only)."));
 } // namespace llvm
 
+extern cl::opt<std::string> UseCtxProfile;
+
 AnalysisKey NoOpModuleAnalysis::Key;
 AnalysisKey NoOpCGSCCAnalysis::Key;
 AnalysisKey NoOpFunctionAnalysis::Key;

llvm/lib/Passes/PassBuilderPipelines.cpp

@@ -304,7 +304,7 @@ static cl::opt<bool> UseLoopVersioningLICM(
     "enable-loop-versioning-licm", cl::init(false), cl::Hidden,
     cl::desc("Enable the experimental Loop Versioning LICM pass"));
 
-static cl::opt<std::string>
+cl::opt<std::string>
     UseCtxProfile("use-ctx-profile", cl::init(""), cl::Hidden,
                   cl::desc("Use the specified contextual profile file"));
 

llvm/lib/Passes/PassRegistry.def

@@ -20,6 +20,7 @@
 #endif
 MODULE_ANALYSIS("callgraph", CallGraphAnalysis())
 MODULE_ANALYSIS("collector-metadata", CollectorMetadataAnalysis())
+MODULE_ANALYSIS("ctx-prof-analysis", CtxProfAnalysis(UseCtxProfile))
 MODULE_ANALYSIS("inline-advisor", InlineAdvisorAnalysis())
 MODULE_ANALYSIS("ir-similarity", IRSimilarityAnalysis())
 MODULE_ANALYSIS("lcg", LazyCallGraphAnalysis())
@@ -79,6 +80,7 @@ MODULE_PASS("insert-gcov-profiling", GCOVProfilerPass())
 MODULE_PASS("instrorderfile", InstrOrderFilePass())
 MODULE_PASS("instrprof", InstrProfilingLoweringPass())
 MODULE_PASS("ctx-instr-lower", PGOCtxProfLoweringPass())
+MODULE_PASS("print<ctx-prof-analysis>", CtxProfAnalysisPrinterPass(dbgs()))
 MODULE_PASS("invalidate<all>", InvalidateAllAnalysesPass())
 MODULE_PASS("iroutliner", IROutlinerPass())
 MODULE_PASS("jmc-instrumenter", JMCInstrumenterPass())

llvm/test/Analysis/CtxProfAnalysis/load.ll

@@ -0,0 +1,56 @@
+; RUN: split-file %s %t
+; RUN: llvm-ctxprof-util fromJSON --input=%t/profile.json --output=%t/profile.ctxprofdata
+; RUN: not opt -passes='require<ctx-prof-analysis>,print<ctx-prof-analysis>' \
+; RUN:   %t/empty.ll -S 2>&1 | FileCheck %s --check-prefix=NO-FILE
+
+; RUN: not opt -passes='require<ctx-prof-analysis>,print<ctx-prof-analysis>' \
+; RUN:   -use-ctx-profile=does_not_exist.ctxprofdata %t/empty.ll -S 2>&1 | FileCheck %s --check-prefix=NO-FILE
+
+; RUN: opt -passes='require<ctx-prof-analysis>,print<ctx-prof-analysis>' \
+; RUN:   -use-ctx-profile=%t/profile.ctxprofdata %t/empty.ll -S 2> %t/output.json
+; RUN: diff %t/profile.json %t/output.json
+
+; NO-FILE: error: could not open contextual profile file
+;
+; This is the reference profile, laid out in the format the json formatter will
+; output it from opt.
+;--- profile.json
+[
+  {
+    "Callsites": [
+      [],
+      [
+        {
+          "Counters": [
+            4,
+            5
+          ],
+          "Guid": 2000
+        },
+        {
+          "Counters": [
+            6,
+            7,
+            8
+          ],
+          "Guid": 18446744073709551613
+        }
+      ]
+    ],
+    "Counters": [
+      1,
+      2,
+      3
+    ],
+    "Guid": 1000
+  },
+  {
+    "Counters": [
+      5,
+      9,
+      10
+    ],
+    "Guid": 18446744073709551612
+  }
+]
+;--- empty.ll