[flang][Driver] Enables lto-partitions and fat-lto-object.

lto-partition helps in performing parallel lto and fat-lto-objects
allows bit code to be embedded in object files generated.

Author: anchuraj

clang/include/clang/Driver/Options.td

@@ -3171,10 +3171,11 @@ def fthin_link_bitcode_EQ : Joined<["-"], "fthin-link-bitcode=">,
   MarshallingInfoString<CodeGenOpts<"ThinLinkBitcodeFile">>;
 defm fat_lto_objects : BoolFOption<"fat-lto-objects",
   CodeGenOpts<"FatLTO">, DefaultFalse,
-  PosFlag<SetTrue, [], [ClangOption, CC1Option], "Enable">,
-  NegFlag<SetFalse, [], [ClangOption, CC1Option], "Disable">,
+  PosFlag<SetTrue, [], [ClangOption, CC1Option, FlangOption, FC1Option], "Enable">,
+  NegFlag<SetFalse, [], [ClangOption, CC1Option, FlangOption, FC1Option], "Disable">,
   BothFlags<[], [ClangOption, CC1Option], " fat LTO object support">>;
 def flto_partitions_EQ : Joined<["-"], "flto-partitions=">, Group<f_Group>,
+  Visibility<[ClangOption, FlangOption]>,
   HelpText<"Number of partitions to use for parallel full LTO codegen, ld.lld only.">;
 def fmacro_backtrace_limit_EQ : Joined<["-"], "fmacro-backtrace-limit=">,
   Group<f_Group>, Visibility<[ClangOption, CC1Option, CLOption]>,

clang/lib/Driver/ToolChains/Flang.cpp

@@ -182,6 +182,29 @@ void Flang::addCodegenOptions(const ArgList &Args,
     CmdArgs.push_back("-fcoarray");
 }
 
+void Flang::addLTOOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
+  const auto &TC = getToolChain();
+  const Driver &D = TC.getDriver();
+  DiagnosticsEngine &Diags = D.getDiags();
+  LTOKind LTOMode = D.getLTOMode();
+  // LTO mode is parsed by the Clang driver library.
+  assert(LTOMode != LTOK_Unknown && "Unknown LTO mode.");
+  if (LTOMode == LTOK_Full)
+    CmdArgs.push_back("-flto=full");
+  else if (LTOMode == LTOK_Thin) {
+    Diags.Report(
+        Diags.getCustomDiagID(DiagnosticsEngine::Warning,
+                              "the option '-flto=thin' is a work in progress"));
+    CmdArgs.push_back("-flto=thin");
+  }
+  if (Args.hasArg(options::OPT_flto_partitions_EQ)) {
+    StringRef A = Args.getLastArgValue(options::OPT_flto_partitions_EQ, "8");
+    CmdArgs.push_back(Args.MakeArgString("-flto-partitions=" + A));
+  }
+  Args.addAllArgs(CmdArgs, {options::OPT_ffat_lto_objects,
+                            options::OPT_fno_fat_lto_objects});
+}
+
 void Flang::addPicOptions(const ArgList &Args, ArgStringList &CmdArgs) const {
   // ParsePICArgs parses -fPIC/-fPIE and their variants and returns a tuple of
   // (RelocationModel, PICLevel, IsPIE).
@@ -821,7 +844,6 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
 
   const Driver &D = TC.getDriver();
   ArgStringList CmdArgs;
-  DiagnosticsEngine &Diags = D.getDiags();
 
   // Invoke ourselves in -fc1 mode.
   CmdArgs.push_back("-fc1");
@@ -884,17 +906,7 @@ void Flang::ConstructJob(Compilation &C, const JobAction &JA,
 
   handleColorDiagnosticsArgs(D, Args, CmdArgs);
 
-  // LTO mode is parsed by the Clang driver library.
-  LTOKind LTOMode = D.getLTOMode();
-  assert(LTOMode != LTOK_Unknown && "Unknown LTO mode.");
-  if (LTOMode == LTOK_Full)
-    CmdArgs.push_back("-flto=full");
-  else if (LTOMode == LTOK_Thin) {
-    Diags.Report(
-        Diags.getCustomDiagID(DiagnosticsEngine::Warning,
-                              "the option '-flto=thin' is a work in progress"));
-    CmdArgs.push_back("-flto=thin");
-  }
+  addLTOOptions(Args, CmdArgs);
 
   // -fPIC and related options.
   addPicOptions(Args, CmdArgs);

clang/lib/Driver/ToolChains/Flang.h

@@ -40,6 +40,14 @@ class LLVM_LIBRARY_VISIBILITY Flang : public Tool {
   void addPreprocessingOptions(const llvm::opt::ArgList &Args,
                                llvm::opt::ArgStringList &CmdArgs) const;
 
+  /// Extract LTO options from the driver arguments and add them to
+  /// the command arguments.
+  ///
+  /// \param [in] Args The list of input driver arguments
+  /// \param [out] CmdArgs The list of output command arguments
+  void addLTOOptions(const llvm::opt::ArgList &Args,
+                     llvm::opt::ArgStringList &CmdArgs) const;
+
   /// Extract PIC options from the driver arguments and add them to
   /// the command arguments.
   ///

flang/include/flang/Frontend/CodeGenOptions.def

@@ -35,6 +35,7 @@ CODEGENOPT(InstrumentFunctions, 1, 0) ///< Set when -finstrument_functions is
 
 CODEGENOPT(IsPIE, 1, 0) ///< PIE level is the same as PIC Level.
 CODEGENOPT(PICLevel, 2, 0) ///< PIC level of the LLVM module.
+CODEGENOPT(PrepareForFatLTO , 1, 0) ///<  Set when -ffat-lto-objects is enabled.
 CODEGENOPT(PrepareForFullLTO , 1, 0) ///< Set when -flto is enabled on the
                                      ///< compile step.
 CODEGENOPT(PrepareForThinLTO , 1, 0) ///< Set when -flto=thin is enabled on the

flang/lib/Frontend/CompilerInvocation.cpp

@@ -325,6 +325,10 @@ static void parseCodeGenArgs(Fortran::frontend::CodeGenOptions &opts,
   if (args.hasArg(clang::driver::options::OPT_finstrument_functions))
     opts.InstrumentFunctions = 1;
 
+  opts.PrepareForFatLTO =
+      args.hasFlag(clang::driver::options::OPT_ffat_lto_objects,
+                   clang::driver::options::OPT_fno_fat_lto_objects, false);
+
   // -flto=full/thin option.
   if (const llvm::opt::Arg *a =
           args.getLastArg(clang::driver::options::OPT_flto_EQ)) {

flang/lib/Frontend/FrontendActions.cpp

@@ -995,7 +995,9 @@ void CodeGenAction::runOptimizationPipeline(llvm::raw_pwrite_stream &os) {
 
   // Create the pass manager.
   llvm::ModulePassManager mpm;
-  if (opts.PrepareForFullLTO)
+  if (opts.PrepareForFatLTO)
+    mpm = pb.buildFatLTODefaultPipeline(level, opts.PrepareForThinLTO, true);
+  else if (opts.PrepareForFullLTO)
     mpm = pb.buildLTOPreLinkDefaultPipeline(level);
   else if (opts.PrepareForThinLTO)
     mpm = pb.buildThinLTOPreLinkDefaultPipeline(level);

flang/test/Driver/lto-fatlto.f90

@@ -0,0 +1,20 @@
+! REQUIRES: x86-registered-target
+! checks fatlto objects: that valid bitcode is included in the object file generated. 
+
+! RUN: %flang -fc1 -triple x86_64-unknown-linux-gnu -flto -ffat-lto-objects -emit-obj %s -o %t.o
+! RUN: llvm-readelf -S %t.o | FileCheck %s --check-prefixes=ELF
+! RUN: llvm-objcopy --dump-section=.llvm.lto=%t.bc %t.o
+! RUN: llvm-dis %t.bc -o - | FileCheck %s --check-prefixes=DIS
+
+! ELF: .llvm.lto
+! DIS: define void @_QQmain()
+! DIS-NEXT:  ret void
+! DIS-NEXT: }
+
+! RUN: %flang -fc1 -triple x86_64-unknown-linux-gnu -flto -ffat-lto-objects -S %s -o - | FileCheck %s --check-prefixes=ASM
+
+!      ASM: .section        .llvm.lto,"e",@llvm_lto
+! ASM-NEXT: .Lllvm.embedded.object:
+! ASM-NEXT:        .asciz  "BC
+! ASM-NEXT: .size   .Lllvm.embedded.object
+end program

flang/test/Driver/lto-lld-flags.f90

@@ -0,0 +1,19 @@
+! UNSUPPORTED: system-windows
+! check flto-partitions is passed to lld, fc1
+! RUN: %flang -### -fuse-ld=lld -flto=full -flto-partitions=16 %s 2>&1 | FileCheck %s --check-prefixes=LLD-PART,FC1-PART
+
+! FC1-PART: "-fc1"
+! FC1-PART-SAME: "-flto=full"
+! FC1-PART-SAME: "-flto-partitions=16"
+! LLD-PART: ld.lld
+! LLD-PART-SAME: "--lto-partitions=16"
+
+! check fat-lto-objects is passed to lld, fc1
+! RUN: %flang -### -fuse-ld=lld -flto -ffat-lto-objects %s 2>&1 | FileCheck %s --check-prefixes=LLD-FAT,FC1-FAT
+
+! FC1-FAT: "-fc1"
+! FC1-FAT-SAME: "-flto=full"
+! FC1-FAT-SAME: "-ffat-lto-objects"
+! LLD-FAT: ld.lld
+! LLD-FAT-SAME: "--fat-lto-objects"
+end program