AnnotationRemarks.cpp

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//===-- AnnotationRemarks.cpp - Generate remarks for annotated instrs. ----===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// Generate remarks for instructions marked with !annotation.
//
//===----------------------------------------------------------------------===//
 
#include "llvm/Transforms/Scalar/AnnotationRemarks.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/Analysis/OptimizationRemarkEmitter.h"
#include "llvm/Analysis/TargetLibraryInfo.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/InstIterator.h"
#include "llvm/IR/Instructions.h"
#include "llvm/IR/IntrinsicInst.h"
#include "llvm/InitializePasses.h"
#include "llvm/Pass.h"
#include "llvm/Support/Debug.h"
#include "llvm/Transforms/Scalar.h"
#include "llvm/Transforms/Utils/AutoInitRemark.h"
 
using namespace llvm;
using namespace llvm::ore;
 
#define DEBUG_TYPE "annotation-remarks"
#define REMARK_PASS DEBUG_TYPE
 
static void tryEmitAutoInitRemark(ArrayRef<Instruction *> Instructions,
                                  OptimizationRemarkEmitter &ORE,
                                  const TargetLibraryInfo &TLI) {
  // For every auto-init annotation generate a separate remark.
  for (Instruction *I : Instructions) {
    if (!I->hasMetadata(LLVMContext::MD_annotation))
      continue;
    for (const MDOperand &Op :
         I->getMetadata(LLVMContext::MD_annotation)->operands()) {
      if (cast<MDString>(Op.get())->getString() != "auto-init")
        continue;
 
      Function &F = *I->getParent()->getParent();
      const DataLayout &DL = F.getParent()->getDataLayout();
      AutoInitRemark Remark(ORE, REMARK_PASS, DL, TLI);
      // For some of them, we can provide more information:
 
      // For stores:
      // * size
      // * volatile / atomic
      if (auto *SI = dyn_cast<StoreInst>(I)) {
        Remark.inspectStore(*SI);
        continue;
      }
 
      // For intrinsics:
      // * user-friendly name
      // * size
      if (auto *II = dyn_cast<IntrinsicInst>(I)) {
        Remark.inspectIntrinsicCall(*II);
        continue;
      }
 
      // For calls:
      // * known/unknown function (e.g. the compiler knows bzero, but it doesn't
      //                                know my_bzero)
      // * memory operation size
      if (auto *CI = dyn_cast<CallInst>(I)) {
        Remark.inspectCall(*CI);
        continue;
      }
 
      Remark.inspectUnknown(*I);
    }
  }
}
 
static void runImpl(Function &F, const TargetLibraryInfo &TLI) {
  if (!OptimizationRemarkEmitter::allowExtraAnalysis(F, REMARK_PASS))
    return;
 
  // Track all annotated instructions aggregated based on their debug location.
  DenseMap<MDNode *, SmallVector<Instruction *, 4>> DebugLoc2Annotated;
 
  OptimizationRemarkEmitter ORE(&F);
  // First, generate a summary of the annotated instructions.
  MapVector<StringRef, unsigned> Mapping;
  for (Instruction &I : instructions(F)) {
    if (!I.hasMetadata(LLVMContext::MD_annotation))
      continue;
    auto Iter = DebugLoc2Annotated.insert({I.getDebugLoc().getAsMDNode(), {}});
    Iter.first->second.push_back(&I);
 
    for (const MDOperand &Op :
         I.getMetadata(LLVMContext::MD_annotation)->operands()) {
      auto Iter = Mapping.insert({cast<MDString>(Op.get())->getString(), 0});
      Iter.first->second++;
    }
  }
 
  for (const auto &KV : Mapping)
    ORE.emit(OptimizationRemarkAnalysis(REMARK_PASS, "AnnotationSummary",
                                        F.getSubprogram(), &F.front())
             << "Annotated " << NV("count", KV.second) << " instructions with "
             << NV("type", KV.first));
 
  // For each debug location, look for all the instructions with annotations and
  // generate more detailed remarks to be displayed at that location.
  for (auto &KV : DebugLoc2Annotated) {
    // Don't generate remarks with no debug location.
    if (!KV.first)
      continue;
 
    tryEmitAutoInitRemark(KV.second, ORE, TLI);
  }
}
 
namespace {
 
struct AnnotationRemarksLegacy : public FunctionPass {
  static char ID;
 
  AnnotationRemarksLegacy() : FunctionPass(ID) {
    initializeAnnotationRemarksLegacyPass(*PassRegistry::getPassRegistry());
  }
 
  bool runOnFunction(Function &F) override {
    const TargetLibraryInfo &TLI =
        getAnalysis<TargetLibraryInfoWrapperPass>().getTLI(F);
    runImpl(F, TLI);
    return false;
  }
 
  void getAnalysisUsage(AnalysisUsage &AU) const override {
    AU.setPreservesAll();
    AU.addRequired<TargetLibraryInfoWrapperPass>();
  }
};
 
} // end anonymous namespace
 
char AnnotationRemarksLegacy::ID = 0;
 
INITIALIZE_PASS_BEGIN(AnnotationRemarksLegacy, "annotation-remarks",
                      "Annotation Remarks", false, false)
INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfoWrapperPass)
INITIALIZE_PASS_END(AnnotationRemarksLegacy, "annotation-remarks",
                    "Annotation Remarks", false, false)
 
FunctionPass *llvm::createAnnotationRemarksLegacyPass() {
  return new AnnotationRemarksLegacy();
}
 
PreservedAnalyses AnnotationRemarksPass::run(Function &F,
                                             FunctionAnalysisManager &AM) {
  auto &TLI = AM.getResult<TargetLibraryAnalysis>(F);
  runImpl(F, TLI);
  return PreservedAnalyses::all();
}