[ThinLTO] Move -lto-use-new-pm to llvm-lto2, and change it to -use-new-pm.

[timshen]

Summary

As we teach Clang to use ThinkLTO + new PM, it's good for the users to
inject through Config, instead of setting a flag in the LTOBackend
library. Move the flag to llvm-lto2.

As it moves to llvm-lto2, a new name -use-new-pm seems simpler and as
clear.

[chandlerc]

(FWIW, I clearly like this patch as I sat with you. Mostly interested in tho folks who have worked on this library confirming they're happy with the API direction.)

[davide]

This is fine by me, in fact, IIRC this was the original approach I proposed, but for some reason we ended up using a cl::opt instead. (@pcc could have ideas on this).
We need to update lld as in all my configs I currently pass -mllvm -use-new-pm everywhere, but that's not a big problem (and given I'm probably the only person on the planet who's using that flag, nobody will be annoyed by the change).
I'll update the linker once this one goes in.

[pcc]

I suggested before that this could be a cl::opt because we were previously not exposing the new PM switch to users. On the assumption that exposing it to users is a good idea (and given that clang has apparently been doing so for the last few months), it seems reasonable enough to add it to config.

llvm/include/llvm/LTO/Config.h

50

Add to computeCacheKey.

[timshen]

Add UseNewPM to computeCacheKey.

[pcc]

LGTM

[davide]

Fine to me if Peter is happy.

[timshen]

Thanks for the quick review!

llvm/include/llvm/LTO/Config.h

struct Config {
   std::vector<std::string> MAttrs;
   Optional<Reloc::Model> RelocModel = Reloc::PIC_;
   CodeModel::Model CodeModel = CodeModel::Default;
   CodeGenOpt::Level CGOptLevel = CodeGenOpt::Default;
   TargetMachine::CodeGenFileType CGFileType = TargetMachine::CGFT_ObjectFile;
   unsigned OptLevel = 2;
   bool DisableVerify = false;
 
+  /// Use the new pass manager
+  bool UseNewPM = false;
+
   /// Disable entirely the optimizer, including importing for ThinLTO
   bool CodeGenOnly = false;
 
   /// If this field is set, the set of passes run in the middle-end optimizer
   /// will be the one specified by the string. Only works with the new pass
   /// manager as the old one doesn't have this ability.
   std::string OptPipeline;
 

llvm/lib/LTO/LTO.cpp

#endif
   if (Conf.RelocModel)
     AddUnsigned(*Conf.RelocModel);
   else
     AddUnsigned(-1);
   AddUnsigned(Conf.CodeModel);
   AddUnsigned(Conf.CGOptLevel);
   AddUnsigned(Conf.CGFileType);
   AddUnsigned(Conf.OptLevel);
+  AddUnsigned(Conf.UseNewPM);
   AddString(Conf.OptPipeline);
   AddString(Conf.AAPipeline);
   AddString(Conf.OverrideTriple);
   AddString(Conf.DefaultTriple);
 
   // Include the hash for the current module
   auto ModHash = Index.getModuleHash(ModuleID);
   Hasher.update(ArrayRef<uint8_t>((uint8_t *)&ModHash[0], sizeof(ModHash)));

llvm/lib/LTO/LTOBackend.cpp

 #include "llvm/Transforms/IPO/PassManagerBuilder.h"
 #include "llvm/Transforms/Scalar/LoopPassManager.h"
 #include "llvm/Transforms/Utils/FunctionImportUtils.h"
 #include "llvm/Transforms/Utils/SplitModule.h"
 
 using namespace llvm;
 using namespace lto;
 
-static cl::opt<bool>
-    LTOUseNewPM("lto-use-new-pm",
-                cl::desc("Run LTO passes using the new pass manager"),
-                cl::init(false), cl::Hidden);
-
 LLVM_ATTRIBUTE_NORETURN static void reportOpenError(StringRef Path, Twine Msg) {
   errs() << "failed to open " << Path << ": " << Msg << '\n';
   errs().flush();
   exit(1);
 }
 
 Error Config::addSaveTemps(std::string OutputFileName,
                            bool UseInputModulePath) {

 
 bool opt(Config &Conf, TargetMachine *TM, unsigned Task, Module &Mod,
          bool IsThinLTO, ModuleSummaryIndex *ExportSummary,
          const ModuleSummaryIndex *ImportSummary) {
   // FIXME: Plumb the combined index into the new pass manager.
   if (!Conf.OptPipeline.empty())
     runNewPMCustomPasses(Mod, TM, Conf.OptPipeline, Conf.AAPipeline,
                          Conf.DisableVerify);
-  else if (LTOUseNewPM)
+  else if (Conf.UseNewPM)
     runNewPMPasses(Mod, TM, Conf.OptLevel, IsThinLTO);
   else
     runOldPMPasses(Conf, Mod, TM, IsThinLTO, ExportSummary, ImportSummary);
   return !Conf.PostOptModuleHook || Conf.PostOptModuleHook(Task, Mod);
 }
 
 void codegen(Config &Conf, TargetMachine *TM, AddStreamFn AddStream,
              unsigned Task, Module &Mod) {

llvm/test/ThinLTO/X86/newpm-basic.ll

 ; RUN: opt -module-summary %s -o %t1.bc
 ; RUN: llvm-lto2 run %t1.bc -o %t.o \
 ; RUN:     -r=%t1.bc,_tinkywinky,pxl \
-; RUN:     -lto-use-new-pm
+; RUN:     -use-new-pm
 
 target datalayout = "e-m:o-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.11.0"
 
 define void @tinkywinky() {
     ret void
 }

llvm/test/tools/llvm-lto2/X86/pipeline.ll

 ; RUN: llvm-as < %s > %t1.bc
 
 ; Try a custom pipeline
 ; RUN: llvm-lto2 run %t1.bc -o %t.o -save-temps \
 ; RUN:  -r %t1.bc,patatino,px -opt-pipeline loweratomic \
 ; RUN:  -aa-pipeline basic-aa
 ; RUN: llvm-dis < %t.o.0.4.opt.bc | FileCheck %s --check-prefix=CUSTOM
 
 ; Try the new pass manager LTO default pipeline (make sure the option
 ; is accepted).
-; RUN: llvm-lto2 run %t1.bc -o %t.o -lto-use-new-pm -r %t1.bc,patatino,px
+; RUN: llvm-lto2 run %t1.bc -o %t.o -use-new-pm -r %t1.bc,patatino,px
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 define void @patatino() {
   fence seq_cst
   ret void
 }

llvm/tools/llvm-lto2/llvm-lto2.cpp

static cl::opt<std::string>
     OptRemarksOutput("pass-remarks-output",
                      cl::desc("YAML output file for optimization remarks"));
 
 static cl::opt<bool> OptRemarksWithHotness(
     "pass-remarks-with-hotness",
     cl::desc("Whether to include hotness informations in the remarks.\n"
              "Has effect only if -pass-remarks-output is specified."));
 
+static cl::opt<bool>
+    UseNewPM("use-new-pm",
+             cl::desc("Run LTO passes using the new pass manager"),
+             cl::init(false), cl::Hidden);
+
 static void check(Error E, std::string Msg) {
   if (!E)
     return;
   handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) {
     errs() << "llvm-lto2: " << Msg << ": " << EIB.message().c_str() << '\n';
   });
   exit(1);
 }
static int run(int argc, char **argv) {
   Conf.RemarksFilename = OptRemarksOutput;
   Conf.RemarksWithHotness = OptRemarksWithHotness;
 
   // Run a custom pipeline, if asked for.
   Conf.OptPipeline = OptPipeline;
   Conf.AAPipeline = AAPipeline;
 
   Conf.OptLevel = OptLevel - '0';
+  Conf.UseNewPM = UseNewPM;
   switch (CGOptLevel) {
   case '0':
     Conf.CGOptLevel = CodeGenOpt::None;
     break;
   case '1':
     Conf.CGOptLevel = CodeGenOpt::Less;
     break;
   case '2':

 int main(int argc, char **argv) {
   InitializeAllTargets();
   InitializeAllTargetMCs();
   InitializeAllAsmPrinters();
   InitializeAllAsmParsers();
 
   // FIXME: This should use llvm::cl subcommands, but it isn't currently
   // possible to pass an argument not associated with a subcommand to a
-  // subcommand (e.g. -lto-use-new-pm).
+  // subcommand (e.g. -use-new-pm).
   if (argc < 2)
     return usage();
 
   StringRef Subcommand = argv[1];
   // Ensure that argv[0] is correct after adjusting argv/argc.
   argv[1] = argv[0];
   if (Subcommand == "dump-symtab")
     return dumpSymtab(argc - 1, argv + 1);
   if (Subcommand == "run")
     return run(argc - 1, argv + 1);
   return usage();
 }