[gold] Add support for optimization remarks

[tejohnson]

Summary

Adds support for LTO opt remarks (optionally with hotness) to
gold-plugin.

[anemet]

Looks pretty straight-forward.

test/tools/gold/X86/opt-remarks.ll

+; Test plugin options for opt-remarks.
+; RUN: llvm-as %s -o %t.o
+; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold%shlibext -shared \
+; RUN:    -plugin-opt=save-temps \
+; RUN:    -plugin-opt=opt-remarks-filename=%t.yaml %t.o -o %t2.o 2>&1
+; RUN: llvm-dis %t2.o.0.4.opt.bc -o - | FileCheck %s
+; RUN: %gold -m elf_x86_64 -plugin %llvmshlibdir/LLVMgold%shlibext -shared \
+; RUN:    -plugin-opt=opt-remarks-with-hotness \
+; RUN:    -plugin-opt=opt-remarks-filename=%t.hot.yaml %t.o -o %t2.o 2>&1
+; RUN: cat %t.yaml | FileCheck %s -check-prefix=YAML
+; RUN: cat %t.hot.yaml | FileCheck %s -check-prefix=YAML-HOT
+
+; Check that @f is inlined after optimizations.
+; CHECK-LABEL: define i32 @_start
+; CHECK-NEXT:  %a.i = call i32 @bar()
+; CHECK-NEXT:  ret i32 %a.i
+; CHECK-NEXT: }
+
+; YAML: --- !Missed
+; YAML-NEXT: Pass:            inline
+; YAML-NEXT: Name:            NoDefinition
+; YAML-NEXT: Function:        f
+; YAML-NEXT: Args:
+; YAML-NEXT:   - Callee:          bar
+; YAML-NEXT:   - String:          ' will not be inlined into '
+; YAML-NEXT:   - Caller:          f
+; YAML-NEXT:   - String:          ' because its definition is unavailable'
+; YAML-NEXT: ...
+; YAML-NEXT: --- !Passed
+; YAML-NEXT: Pass:            inline
+; YAML-NEXT: Name:            Inlined
+; YAML-NEXT: Function:        _start
+; YAML-NEXT: Args:
+; YAML-NEXT:   - Callee:          f
+; YAML-NEXT:   - String:          ' inlined into '
+; YAML-NEXT:   - Caller:          _start
+; YAML-NEXT:   - String:          ' with cost='
+; YAML-NEXT:   - Cost:            '0'
+; YAML-NEXT:   - String:          ' (threshold='
+; YAML-NEXT:   - Threshold:       '337'
+; YAML-NEXT:   - String:          ')'
+; YAML-NEXT: ...
+
+; YAML-HOT: ...
+; YAML-HOT: --- !Passed
+; YAML-HOT: Pass:            inline
+; YAML-HOT-NEXT: Name:            Inlined
+; YAML-HOT-NEXT: Function:        _start
+; YAML-HOT-NEXT: Hotness:         300
+; YAML-HOT-NEXT: Args:
+; YAML-HOT-NEXT:   - Callee:          f
+; YAML-HOT-NEXT:   - String:          ' inlined into '
+; YAML-HOT-NEXT:   - Caller:          _start
+; YAML-HOT-NEXT:   - String:          ' with cost='
+; YAML-HOT-NEXT:   - Cost:            '0'
+; YAML-HOT-NEXT:   - String:          ' (threshold='
+; YAML-HOT-NEXT:   - Threshold:       '337'
+; YAML-HOT-NEXT:   - String:          ')'
+; YAML-HOT-NEXT: ...
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i32 @bar()
+
+define i32 @f() {
+  %a = call i32 @bar()
+  ret i32 %a
+}
+
+define i32 @_start() !prof !0 {
+  %call = call i32 @f()
+  ret i32 %call
+}
+
+!0 = !{!"function_entry_count", i64 300}

tools/gold/gold-plugin.cpp

#endif
   static bool new_pass_manager = false;
   // Debug new pass manager
   static bool debug_pass_manager = false;
   // Objcopy for debug fission.
   static std::string objcopy;
   // Directory to store the .dwo files.
   static std::string dwo_dir;
 
+  // Optimization remarks filename and hotness options
+  static std::string OptRemarksFilename;
+  static bool OptRemarksWithHotness = false;
+
   static void process_plugin_option(const char *opt_)
   {
     if (opt_ == nullptr)
       return;
     llvm::StringRef opt = opt_;
 
     if (opt.startswith("mcpu=")) {
       mcpu = opt.substr(strlen("mcpu="));
static void process_plugin_option(const char *opt_)
     } else if (opt == "new-pass-manager") {
       new_pass_manager = true;
     } else if (opt == "debug-pass-manager") {
       debug_pass_manager = true;
     } else if (opt.startswith("objcopy=")) {
       objcopy = opt.substr(strlen("objcopy="));
     } else if (opt.startswith("dwo_dir=")) {
       dwo_dir = opt.substr(strlen("dwo_dir="));
+    } else if (opt.startswith("opt-remarks-filename=")) {
+      OptRemarksFilename = opt.substr(strlen("opt-remarks-filename="));
+    } else if (opt == "opt-remarks-with-hotness") {
+      OptRemarksWithHotness = true;
     } else {
       // Save this option to pass to the code generator.
       // ParseCommandLineOptions() expects argv[0] to be program name. Lazily
       // add that.
       if (extra.empty())
         extra.push_back("LLVMgold");
 
       extra.push_back(opt_);
static std::unique_ptr<LTO> createLTO(IndexWriteCallback OnIndexWrite,
 
   if (!options::sample_profile.empty())
     Conf.SampleProfile = options::sample_profile;
 
   Conf.DwoDir = options::dwo_dir;
 
   Conf.Objcopy = options::objcopy;
 
+  // Set up optimization remarks handling.
+  Conf.RemarksFilename = options::OptRemarksFilename;
+  Conf.RemarksWithHotness = options::OptRemarksWithHotness;
+
   // Use new pass manager if set in driver
   Conf.UseNewPM = options::new_pass_manager;
   // Debug new pass manager if requested
   Conf.DebugPassManager = options::debug_pass_manager;
 
   return llvm::make_unique<LTO>(std::move(Conf), Backend,
                                 options::ParallelCodeGenParallelismLevel);
 }