Add a CC1 option to enable the Swift function-merging pass

Patch by Linus Nilsson.

Author: vedantk

include/clang/Driver/CC1Options.td

@@ -217,6 +217,8 @@ def fdump_vtable_layouts : Flag<["-"], "fdump-vtable-layouts">,
   HelpText<"Dump the layouts of all vtables that will be emitted in a translation unit">;
 def fmerge_functions : Flag<["-"], "fmerge-functions">,
   HelpText<"Permit merging of identical functions when optimizing.">;
+def fmerge_similar_functions : Flag<["-"], "fmerge-similar-functions">,
+  HelpText<"Permit merging of similar functions when optimizing.">;
 def femit_coverage_notes : Flag<["-"], "femit-coverage-notes">,
   HelpText<"Emit a gcov coverage notes file when compiling.">;
 def femit_coverage_data: Flag<["-"], "femit-coverage-data">,

include/clang/Frontend/CodeGenOptions.def

@@ -119,6 +119,7 @@ CODEGENOPT(IncrementalLinkerCompatible, 1, 0) ///< Emit an object file which can
                                               ///< linker.
 CODEGENOPT(MergeAllConstants , 1, 1) ///< Merge identical constants.
 CODEGENOPT(MergeFunctions    , 1, 0) ///< Set when -fmerge-functions is enabled.
+CODEGENOPT(MergeSimilarFunctions , 1, 0) ///< Set when -fmerge-similar-functions is enabled.
 CODEGENOPT(MSVolatile        , 1, 0) ///< Set when /volatile:ms is enabled.
 CODEGENOPT(NoCommon          , 1, 0) ///< Set when -fno-common or C++ is enabled.
 CODEGENOPT(NoDwarfDirectoryAsm , 1, 0) ///< Set when -fno-dwarf-directory-asm is

lib/CodeGen/BackendUtil.cpp

@@ -535,6 +535,7 @@ void EmitAssemblyHelper::CreatePasses(legacy::PassManager &MPM,
 
   PMBuilder.DisableUnrollLoops = !CodeGenOpts.UnrollLoops;
   PMBuilder.MergeFunctions = CodeGenOpts.MergeFunctions;
+  PMBuilder.MergeSimilarFunctions = CodeGenOpts.MergeSimilarFunctions;
   PMBuilder.PrepareForThinLTO = CodeGenOpts.PrepareForThinLTO;
   PMBuilder.PrepareForLTO = CodeGenOpts.PrepareForLTO;
   PMBuilder.RerollLoops = CodeGenOpts.RerollLoops;

lib/Driver/ToolChains/Clang.cpp

@@ -3407,6 +3407,12 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                    options::OPT_fdelete_null_pointer_checks, false))
     CmdArgs.push_back("-fno-delete-null-pointer-checks");
 
+  if (Args.hasArg(options::OPT_fmerge_similar_functions))
+    CmdArgs.push_back("-fmerge-similar-functions");
+
+  if (Args.hasArg(options::OPT_fmerge_functions))
+    CmdArgs.push_back("-fmerge-functions");
+
   // LLVM Code Generator Options.
 
   if (Args.hasArg(options::OPT_frewrite_map_file) ||

lib/Frontend/CompilerInvocation.cpp

@@ -743,6 +743,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
                                          OPT_fno_unique_section_names, true);
 
   Opts.MergeFunctions = Args.hasArg(OPT_fmerge_functions);
+  Opts.MergeSimilarFunctions = Args.hasArg(OPT_fmerge_similar_functions);
 
   Opts.NoUseJumpTables = Args.hasArg(OPT_fno_jump_tables);
 

test/CodeGenCXX/merge-functions.cpp

@@ -1,5 +1,5 @@
 // REQUIRES: x86-registered-target
-// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O1 -fmerge-functions -emit-llvm -o - -x c++ < %s | FileCheck %s
+// RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -O1 -fmerge-functions -fmerge-similar-functions -emit-llvm -o - -x c++ < %s | FileCheck %s
 
 // Basic functionality test. Function merging doesn't kick in on functions that
 // are too simple.