[LTO][ELF] Add --stats-file= option.

[MTC]

Summary

This patch adds a StatsFile option supported by gold to lld, related patch https://reviews.llvm.org/D45531.

[tejohnson]

lgtm. Few minor comments to address below before submitting.

lld/ELF/LTO.cpp

145

nit: s/Setup/Set up/

lld/test/ELF/lto/stats-file-option.ll

4

Nit: I believe the new convention in this test directory at least is to prefix comments with two semicolons.

5

nit: looks like no need to split this command into 2 lines to fit into 80 chars

[MaskRay]

([lld] may be thought of applying to all lld ports: COFF, ELF, MachO, wasm. I usually use [ELF] to indicate ELF specific changes).

stats-file option => --stats-file=

lld/test/ELF/lto/stats-file-option.ll

16

[MTC]

NFC, improve the comments and the test.

[MTC]

Thanks for all the kind comments, I have updated the patch.

[tejohnson]

lgtm

[MTC]

Sorry to interrupt, seems this patch caused the build failure, see https://lab.llvm.org/buildbot/#/builders/124/builds/3944. I don't have any clue why this failed, Did I miss something for the test file? Like ; REQUIRES: x86 is indispensable?

[tejohnson]

In D121809#3388287, @MTC wrote:

Sorry to interrupt, seems this patch caused the build failure, see https://lab.llvm.org/buildbot/#/builders/124/builds/3944. I don't have any clue why this failed, Did I miss something for the test file? Like ; REQUIRES: x86 is indispensable?

Ah, for stats printing I believe you need a "REQUIRES: asserts"

[MTC]

In D121809#3388356, @tejohnson wrote:

In D121809#3388287, @MTC wrote:

Sorry to interrupt, seems this patch caused the build failure, see https://lab.llvm.org/buildbot/#/builders/124/builds/3944. I don't have any clue why this failed, Did I miss something for the test file? Like ; REQUIRES: x86 is indispensable?

Ah, for stats printing I believe you need a "REQUIRES: asserts"

Very much appreciate your help, I will dig into it so as not to screw things up.

lld/ELF/Config.h

struct Configuration {
   llvm::StringRef ltoObjPath;
   llvm::StringRef ltoSampleProfile;
   llvm::StringRef mapFile;
   llvm::StringRef outputFile;
   llvm::StringRef optRemarksFilename;
   llvm::Optional<uint64_t> optRemarksHotnessThreshold = 0;
   llvm::StringRef optRemarksPasses;
   llvm::StringRef optRemarksFormat;
+  llvm::StringRef optStatsFilename;
   llvm::StringRef progName;
   llvm::StringRef printArchiveStats;
   llvm::StringRef printSymbolOrder;
   llvm::StringRef soName;
   llvm::StringRef sysroot;
   llvm::StringRef thinLTOCacheDir;
   llvm::StringRef thinLTOIndexOnlyArg;
   llvm::StringRef whyExtract;

lld/ELF/Driver.cpp

static void readConfigs(opt::InputArgList &args) {
   config->mmapOutputFile =
       args.hasFlag(OPT_mmap_output_file, OPT_no_mmap_output_file, true);
   config->nmagic = args.hasFlag(OPT_nmagic, OPT_no_nmagic, false);
   config->noinhibitExec = args.hasArg(OPT_noinhibit_exec);
   config->nostdlib = args.hasArg(OPT_nostdlib);
   config->oFormatBinary = isOutputFormatBinary(args);
   config->omagic = args.hasFlag(OPT_omagic, OPT_no_omagic, false);
   config->optRemarksFilename = args.getLastArgValue(OPT_opt_remarks_filename);
+  config->optStatsFilename = args.getLastArgValue(OPT_opt_stats_filename);
 
   // Parse remarks hotness threshold. Valid value is either integer or 'auto'.
   if (auto *arg = args.getLastArg(OPT_opt_remarks_hotness_threshold)) {
     auto resultOrErr = remarks::parseHotnessThresholdOption(arg->getValue());
     if (!resultOrErr)
       error(arg->getSpelling() + ": invalid argument '" + arg->getValue() +
             "', only integer or 'auto' is supported");
     else

lld/ELF/LTO.cpp

static lto::Config createConfig() {
 
   // Set up optimization remarks if we've been asked to.
   c.RemarksFilename = std::string(config->optRemarksFilename);
   c.RemarksPasses = std::string(config->optRemarksPasses);
   c.RemarksWithHotness = config->optRemarksWithHotness;
   c.RemarksHotnessThreshold = config->optRemarksHotnessThreshold;
   c.RemarksFormat = std::string(config->optRemarksFormat);
 
+  // Set up output file to emit statistics.
+  c.StatsFile = std::string(config->optStatsFilename);
+
   c.SampleProfile = std::string(config->ltoSampleProfile);
   c.UseNewPM = config->ltoNewPassManager;
   c.DebugPassManager = config->ltoDebugPassManager;
   c.DwoDir = std::string(config->dwoDir);
 
   c.HasWholeProgramVisibility = config->ltoWholeProgramVisibility;
   c.AlwaysEmitRegularLTOObj = !config->ltoObjPath.empty();
 

lld/ELF/Options.td

defm opt_remarks_hotness_threshold: EEq<"opt-remarks-hotness-threshold",
   " Use 'auto' to apply the threshold from profile summary.">,
   MetaVarName<"<value>">;
 def opt_remarks_passes: Separate<["--"], "opt-remarks-passes">,
   HelpText<"Regex for the passes that need to be serialized to the output file">;
 def opt_remarks_with_hotness: FF<"opt-remarks-with-hotness">,
   HelpText<"Include hotness information in the optimization remarks file">;
 def opt_remarks_format: Separate<["--"], "opt-remarks-format">,
   HelpText<"The format used for serializing remarks (default: YAML)">;
+def opt_stats_filename: JJ<"stats-file=">,
+  HelpText<"Filename to write statistics to">;
 def save_temps: F<"save-temps">, HelpText<"Save intermediate LTO compilation results">;
 def lto_basic_block_sections: JJ<"lto-basic-block-sections=">,
   HelpText<"Enable basic block sections for LTO">;
 defm lto_unique_basic_block_section_names: BB<"lto-unique-basic-block-section-names",
     "Give unique names to every basic block section for LTO",
     "Do not give unique names to every basic block section for LTO (default)">;
 defm shuffle_sections: EEq<"shuffle-sections",
   "Shuffle matched sections using the given seed before mapping them to the output sections. "

lld/test/ELF/lto/stats-file-option.ll

+; RUN: llvm-as -o %t.bc %s
+
+;; Try to save statistics to file.
+; RUN: ld.lld --stats-file=%t2.stats -m elf_x86_64 -r -o %t.o %t.bc
+; RUN: FileCheck --input-file=%t2.stats %s
+
+; CHECK: {
+; CHECK: "asm-printer.EmittedInsts":
+; CHECK: "inline.NumInlined":
+; CHECK: "prologepilog.NumFuncSeen":
+; CHECK: }
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i32 @patatino()
+
+define i32 @tinkywinky() {
+  %a = call i32 @patatino()
+  ret i32 %a
+}
+
+define i32 @main() !prof !0 {
+  %i = call i32 @tinkywinky()
+  ret i32 %i
+}
+
+!0 = !{!"function_entry_count", i64 300}