Commit 31ae0165 authored by Gabor Horvath's avatar Gabor Horvath
Browse files

[LTO] Add optimization remarks for removed functions 

This only works with regular LTO for now.

Differential Revision: https://reviews.llvm.org/D73597
parent a10cec02

llvm/include/llvm/LTO/LTOBackend.h

+3 −0
Original line number Diff line number Diff line
@@ -45,6 +45,9 @@ Error thinBackend(const Config &C, unsigned Task, AddStreamFn AddStream, 
                  const FunctionImporter::ImportMapTy &ImportList,

                  const GVSummaryMapTy &DefinedGlobals,

                  MapVector<StringRef, BitcodeModule> &ModuleMap);



Error finalizeOptimizationRemarks(

    std::unique_ptr<ToolOutputFile> DiagOutputFile);

}

}

llvm/lib/IR/DiagnosticInfo.cpp

+3 −6
Original line number Diff line number Diff line
@@ -244,11 +244,8 @@ OptimizationRemark::OptimizationRemark(const char *PassName, 
                                   RemarkName, *Inst->getParent()->getParent(),

                                   Inst->getDebugLoc(), Inst->getParent()) {}



// Helper to allow for an assert before attempting to return an invalid

// reference.

static const BasicBlock &getFirstFunctionBlock(const Function *Func) {

  assert(!Func->empty() && "Function does not have a body");

  return Func->front();

static const BasicBlock *getFirstFunctionBlock(const Function *Func) {

  return Func->empty() ? nullptr : &Func->front();

}



OptimizationRemark::OptimizationRemark(const char *PassName,
@@ -256,7 +253,7 @@ OptimizationRemark::OptimizationRemark(const char *PassName, 
                                       const Function *Func)

    : DiagnosticInfoIROptimization(DK_OptimizationRemark, DS_Remark, PassName,

                                   RemarkName, *Func, Func->getSubprogram(),

                                   &getFirstFunctionBlock(Func)) {}

                                   getFirstFunctionBlock(Func)) {}



bool OptimizationRemark::isEnabled() const {

  const Function &Fn = getFunction();

llvm/lib/LTO/LTO.cpp

+36 −14
Original line number Diff line number Diff line
@@ -12,6 +12,7 @@ 


#include "llvm/LTO/LTO.h"

#include "llvm/ADT/Statistic.h"

#include "llvm/Analysis/OptimizationRemarkEmitter.h"

#include "llvm/Analysis/TargetLibraryInfo.h"

#include "llvm/Analysis/TargetTransformInfo.h"

#include "llvm/Bitcode/BitcodeReader.h"
@@ -781,8 +782,15 @@ Error LTO::linkRegularLTO(RegularLTOState::AddedModule Mod, 
                          bool LivenessFromIndex) {

  std::vector<GlobalValue *> Keep;

  for (GlobalValue *GV : Mod.Keep) {

    if (LivenessFromIndex && !ThinLTO.CombinedIndex.isGUIDLive(GV->getGUID()))

    if (LivenessFromIndex && !ThinLTO.CombinedIndex.isGUIDLive(GV->getGUID())) {

      if (Function *F = dyn_cast<Function>(GV)) {

        OptimizationRemarkEmitter ORE(F);

        ORE.emit(OptimizationRemark(DEBUG_TYPE, "deadfunction", F)

                 << ore::NV("Function", F)

                 << " not added to the combined module ");

      }

      continue;

    }



    if (!GV->hasAvailableExternallyLinkage()) {

      Keep.push_back(GV);
@@ -931,17 +939,6 @@ Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) { 
    return StatsFileOrErr.takeError();

  std::unique_ptr<ToolOutputFile> StatsFile = std::move(StatsFileOrErr.get());



  // Finalize linking of regular LTO modules containing summaries now that

  // we have computed liveness information.

  for (auto &M : RegularLTO.ModsWithSummaries)

    if (Error Err = linkRegularLTO(std::move(M),

                                   /*LivenessFromIndex=*/true))

      return Err;



  // Ensure we don't have inconsistently split LTO units with type tests.

  if (Error Err = checkPartiallySplit())

    return Err;



  Error Result = runRegularLTO(AddStream);

  if (!Result)

    Result = runThinLTO(AddStream, Cache, GUIDPreservedSymbols);
@@ -953,6 +950,27 @@ Error LTO::run(AddStreamFn AddStream, NativeObjectCache Cache) { 
}



Error LTO::runRegularLTO(AddStreamFn AddStream) {

  // Setup optimization remarks.

  auto DiagFileOrErr = lto::setupOptimizationRemarks(

      RegularLTO.CombinedModule->getContext(), Conf.RemarksFilename,

      Conf.RemarksPasses, Conf.RemarksFormat, Conf.RemarksWithHotness);

  if (!DiagFileOrErr)

    return DiagFileOrErr.takeError();



  // Finalize linking of regular LTO modules containing summaries now that

  // we have computed liveness information.

  for (auto &M : RegularLTO.ModsWithSummaries)

    if (Error Err = linkRegularLTO(std::move(M),

                                   /*LivenessFromIndex=*/true))

      return Err;



  // Ensure we don't have inconsistently split LTO units with type tests.

  // FIXME: this checks both LTO and ThinLTO. It happens to work as we take

  // this path both cases but eventually this should be split into two and

  // do the ThinLTO checks in `runThinLTO`.

  if (Error Err = checkPartiallySplit())

    return Err;



  // Make sure commons have the right size/alignment: we kept the largest from

  // all the prevailing when adding the inputs, and we apply it here.

  const DataLayout &DL = RegularLTO.CombinedModule->getDataLayout();
@@ -1017,8 +1035,12 @@ Error LTO::runRegularLTO(AddStreamFn AddStream) { 
        !Conf.PostInternalizeModuleHook(0, *RegularLTO.CombinedModule))

      return Error::success();

  }

  return backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,

                 std::move(RegularLTO.CombinedModule), ThinLTO.CombinedIndex);

  if (Error Err =

          backend(Conf, AddStream, RegularLTO.ParallelCodeGenParallelismLevel,

                  std::move(RegularLTO.CombinedModule), ThinLTO.CombinedIndex))

    return Err;



  return finalizeOptimizationRemarks(std::move(*DiagFileOrErr));

}



static const char *libcallRoutineNames[] = {

llvm/lib/LTO/LTOBackend.cpp

+4 −12
Original line number Diff line number Diff line
@@ -434,8 +434,8 @@ Expected<const Target *> initAndLookupTarget(const Config &C, Module &Mod) { 
}

}



static Error

finalizeOptimizationRemarks(std::unique_ptr<ToolOutputFile> DiagOutputFile) {

Error lto::finalizeOptimizationRemarks(

    std::unique_ptr<ToolOutputFile> DiagOutputFile) {

  // Make sure we flush the diagnostic remarks file in case the linker doesn't

  // call the global destructors before exiting.

  if (!DiagOutputFile)
@@ -455,18 +455,10 @@ Error lto::backend(const Config &C, AddStreamFn AddStream, 


  std::unique_ptr<TargetMachine> TM = createTargetMachine(C, *TOrErr, *Mod);



  // Setup optimization remarks.

  auto DiagFileOrErr = lto::setupOptimizationRemarks(

      Mod->getContext(), C.RemarksFilename, C.RemarksPasses, C.RemarksFormat,

      C.RemarksWithHotness);

  if (!DiagFileOrErr)

    return DiagFileOrErr.takeError();

  auto DiagnosticOutputFile = std::move(*DiagFileOrErr);



  if (!C.CodeGenOnly) {

    if (!opt(C, TM.get(), 0, *Mod, /*IsThinLTO=*/false,

             /*ExportSummary=*/&CombinedIndex, /*ImportSummary=*/nullptr))

      return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));

      return Error::success();

  }



  if (ParallelCodeGenParallelismLevel == 1) {
@@ -475,7 +467,7 @@ Error lto::backend(const Config &C, AddStreamFn AddStream, 
    splitCodeGen(C, TM.get(), AddStream, ParallelCodeGenParallelismLevel,

                 std::move(Mod));

  }

  return finalizeOptimizationRemarks(std::move(DiagnosticOutputFile));

  return Error::success();

}



static void dropDeadSymbols(Module &Mod, const GVSummaryMapTy &DefinedGlobals,

llvm/test/LTO/Resolution/X86/dead-strip-fulllto.ll

+13 −3
Original line number Diff line number Diff line 
; RUN: opt -module-summary -o %t %s

; RUN: opt -module-summary -o %t2 %S/Inputs/dead-strip-fulllto.ll



; RUN: llvm-lto2 run %t -r %t,main,px -r %t,live1, -r %t,live2,p -r %t,dead2,p \

; RUN: llvm-lto2 run --pass-remarks-output=%t4.yaml --pass-remarks-filter=. \

; RUN:               %t -r %t,main,px -r %t,live1, -r %t,live2,p -r %t,dead2,p \

; RUN:               %t2 -r %t2,live1,p -r %t2,live2, -r %t2,dead1,p -r %t2,dead2, -r %t2,odr, \

; RUN:               -save-temps -o %t3



; RUN: cat %t4.yaml | FileCheck %s -check-prefix=REMARK

; RUN: llvm-nm %t3.0 | FileCheck --check-prefix=FULL %s

; RUN: llvm-nm %t3.1 | FileCheck --check-prefix=THIN %s
@@ -13,6 +16,13 @@ 
; RUN: llvm-nm %t3.0 | FileCheck --check-prefix=FULL %s

; RUN: llvm-nm %t3.1 | FileCheck --check-prefix=THIN %s



; REMARK:      Pass:            lto

; REMARK-NEXT: Name:            deadfunction

; REMARK-NEXT: Function:        dead2

; REMARK-NEXT: Args:

; REMARK-NEXT:   - Function:        dead2

; REMARK-NEXT:   - String:          ' not added to the combined module '



; FULL-NOT: dead

; FULL: U live1

; FULL: T live2