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

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

Reviewed By: tejohnson, MaskRay

Differential Revision: https://reviews.llvm.org/D121809

Author: movie-travel-code

lld/ELF/Config.h

@@ -122,6 +122,7 @@ struct Configuration {
   llvm::Optional<uint64_t> optRemarksHotnessThreshold = 0;
   llvm::StringRef optRemarksPasses;
   llvm::StringRef optRemarksFormat;
+  llvm::StringRef optStatsFilename;
   llvm::StringRef progName;
   llvm::StringRef printArchiveStats;
   llvm::StringRef printSymbolOrder;

lld/ELF/Driver.cpp

@@ -1103,6 +1103,7 @@ static void readConfigs(opt::InputArgList &args) {
   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)) {

lld/ELF/LTO.cpp

@@ -142,6 +142,9 @@ static lto::Config createConfig() {
   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;

lld/ELF/Options.td

@@ -583,6 +583,8 @@ 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">;

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

@@ -0,0 +1,28 @@
+; 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}