Revert "[clang] Preliminary fat-lto-object support"

FatLTO support is only half complete, and shouldn't be included in the
17.x release. https://reviews.llvm.org/D152973.

This reverts commit 5784c47.
This reverts commit 610fc5c.

Author: ilovepi

clang/docs/ReleaseNotes.rst

@@ -309,10 +309,6 @@ Modified Compiler Flags
   directory (``/tmp`` on \*NIX systems, if none of the environment variables
   TMPDIR, TMP, and TEMP are specified).
 
-- ``-ffat-lto-objects`` can now be used to emit object files with both object
-  code and LLVM bitcode. Previously this flag was ignored for GCC compatibility.
-  (`See related patch <https://reviews.llvm.org/D146777>`_).
-
 Removed Compiler Flags
 -------------------------
 - The deprecated flag `-fmodules-ts` is removed. Please use ``-std=c++20``

clang/include/clang/Basic/CodeGenOptions.def

@@ -165,7 +165,6 @@ CODEGENOPT(PrepareForThinLTO , 1, 0) ///< Set when -flto=thin is enabled on the
                                      ///< compile step.
 CODEGENOPT(LTOUnit, 1, 0) ///< Emit IR to support LTO unit features (CFI, whole
                           ///< program vtable opt).
-CODEGENOPT(FatLTO, 1, 0) ///< Set when -ffat-lto-objects is enabled.
 CODEGENOPT(EnableSplitLTOUnit, 1, 0) ///< Enable LTO unit splitting to support
 				     /// CFI and traditional whole program
 				     /// devirtualization that require whole

clang/include/clang/Driver/Options.td

@@ -2375,11 +2375,6 @@ def fthin_link_bitcode_EQ : Joined<["-"], "fthin-link-bitcode=">,
   Flags<[CoreOption, CC1Option]>, Group<f_Group>,
   HelpText<"Write minimized bitcode to <file> for the ThinLTO thin link only">,
   MarshallingInfoString<CodeGenOpts<"ThinLinkBitcodeFile">>;
-defm fat_lto_objects : BoolFOption<"fat-lto-objects",
-  CodeGenOpts<"FatLTO">, DefaultFalse,
-  PosFlag<SetTrue, [CC1Option], "Enable">,
-  NegFlag<SetFalse, [CC1Option], "Disable">,
-  BothFlags<[CC1Option], " fat LTO object support">>;
 def fmacro_backtrace_limit_EQ : Joined<["-"], "fmacro-backtrace-limit=">,
   Group<f_Group>, Flags<[NoXarchOption, CC1Option, CoreOption]>,
   HelpText<"Set the maximum number of entries to print in a macro expansion backtrace (0 = no limit)">,
@@ -5162,6 +5157,7 @@ defm caller_saves : BooleanFFlag<"caller-saves">, Group<clang_ignored_gcc_optimi
 defm reorder_blocks : BooleanFFlag<"reorder-blocks">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm branch_count_reg : BooleanFFlag<"branch-count-reg">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm default_inline : BooleanFFlag<"default-inline">, Group<clang_ignored_gcc_optimization_f_Group>;
+defm fat_lto_objects : BooleanFFlag<"fat-lto-objects">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm float_store : BooleanFFlag<"float-store">, Group<clang_ignored_gcc_optimization_f_Group>;
 defm friend_injection : BooleanFFlag<"friend-injection">, Group<clang_ignored_f_Group>;
 defm function_attribute_list : BooleanFFlag<"function-attribute-list">, Group<clang_ignored_f_Group>;

clang/lib/CodeGen/BackendUtil.cpp

@@ -55,7 +55,6 @@
 #include "llvm/Target/TargetOptions.h"
 #include "llvm/TargetParser/SubtargetFeature.h"
 #include "llvm/TargetParser/Triple.h"
-#include "llvm/Transforms/IPO/EmbedBitcodePass.h"
 #include "llvm/Transforms/IPO/LowerTypeTests.h"
 #include "llvm/Transforms/IPO/ThinLTOBitcodeWriter.h"
 #include "llvm/Transforms/InstCombine/InstCombine.h"
@@ -1016,12 +1015,7 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
           });
     }
 
-    bool IsThinOrUnifiedLTO = IsThinLTO || (IsLTO && CodeGenOpts.UnifiedLTO);
-    if (CodeGenOpts.FatLTO) {
-      MPM = PB.buildFatLTODefaultPipeline(Level, IsThinOrUnifiedLTO,
-                                          IsThinOrUnifiedLTO ||
-                                              shouldEmitRegularLTOSummary());
-    } else if (IsThinOrUnifiedLTO) {
+    if (IsThinLTO || (IsLTO && CodeGenOpts.UnifiedLTO)) {
       MPM = PB.buildThinLTOPreLinkDefaultPipeline(Level);
     } else if (IsLTO) {
       MPM = PB.buildLTOPreLinkDefaultPipeline(Level);
@@ -1077,21 +1071,6 @@ void EmitAssemblyHelper::RunOptimizationPipeline(
                                     EmitLTOSummary));
     }
   }
-  if (CodeGenOpts.FatLTO) {
-    // Set module flags, like EnableSplitLTOUnit and UnifiedLTO, since FatLTO
-    // uses a different action than Backend_EmitBC or Backend_EmitLL.
-    bool IsThinOrUnifiedLTO =
-        CodeGenOpts.PrepareForThinLTO ||
-        (CodeGenOpts.PrepareForLTO && CodeGenOpts.UnifiedLTO);
-    if (!TheModule->getModuleFlag("ThinLTO"))
-      TheModule->addModuleFlag(Module::Error, "ThinLTO",
-                               uint32_t(IsThinOrUnifiedLTO));
-    if (!TheModule->getModuleFlag("EnableSplitLTOUnit"))
-      TheModule->addModuleFlag(Module::Error, "EnableSplitLTOUnit",
-                               uint32_t(CodeGenOpts.EnableSplitLTOUnit));
-    if (CodeGenOpts.UnifiedLTO && !TheModule->getModuleFlag("UnifiedLTO"))
-      TheModule->addModuleFlag(Module::Error, "UnifiedLTO", uint32_t(1));
-  }
 
   // Now that we have all of the passes ready, run them.
   {

clang/lib/Driver/Driver.cpp

@@ -4741,13 +4741,8 @@ Action *Driver::ConstructPhaseAction(
   }
   case phases::Backend: {
     if (isUsingLTO() && TargetDeviceOffloadKind == Action::OFK_None) {
-      types::ID Output;
-      if (Args.hasArg(options::OPT_S))
-        Output = types::TY_LTO_IR;
-      else if (Args.hasArg(options::OPT_ffat_lto_objects))
-        Output = types::TY_PP_Asm;
-      else
-        Output = types::TY_LTO_BC;
+      types::ID Output =
+          Args.hasArg(options::OPT_S) ? types::TY_LTO_IR : types::TY_LTO_BC;
       return C.MakeAction<BackendJobAction>(Input, Output);
     }
     if (isUsingLTO(/* IsOffload */ true) &&

clang/lib/Driver/ToolChains/Clang.cpp

@@ -7376,22 +7376,6 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   if (SplitLTOUnit)
     CmdArgs.push_back("-fsplit-lto-unit");
 
-  if (Arg *A = Args.getLastArg(options::OPT_ffat_lto_objects,
-                               options::OPT_fno_fat_lto_objects)) {
-    if (IsUsingLTO && A->getOption().matches(options::OPT_ffat_lto_objects)) {
-      assert(LTOMode == LTOK_Full || LTOMode == LTOK_Thin);
-      if (!Triple.isOSBinFormatELF()) {
-        D.Diag(diag::err_drv_unsupported_opt_for_target)
-            << A->getAsString(Args) << TC.getTripleString();
-      }
-      CmdArgs.push_back(Args.MakeArgString(
-          Twine("-flto=") + (LTOMode == LTOK_Thin ? "thin" : "full")));
-      CmdArgs.push_back("-flto-unit");
-      CmdArgs.push_back("-ffat-lto-objects");
-      A->render(Args, CmdArgs);
-    }
-  }
-
   if (Arg *A = Args.getLastArg(options::OPT_fglobal_isel,
                                options::OPT_fno_global_isel)) {
     CmdArgs.push_back("-mllvm");

clang/lib/Driver/ToolChains/CommonArgs.cpp

@@ -621,11 +621,6 @@ void tools::addLTOOptions(const ToolChain &ToolChain, const ArgList &Args,
                                 PluginName + Suffix,
                             Plugin);
     CmdArgs.push_back(Args.MakeArgString(Twine(PluginPrefix) + Plugin));
-  } else {
-    // Tell LLD to find and use .llvm.lto section in regular relocatable object
-    // files
-    if (Args.hasArg(options::OPT_ffat_lto_objects))
-      CmdArgs.push_back("--fat-lto-objects");
   }
 
   const char *PluginOptPrefix = IsOSAIX ? "-bplugin_opt:" : "-plugin-opt=";

clang/test/CodeGen/fat-lto-objects.c

@@ -424,6 +424,7 @@
 // CHECK-WARNING-DAG: optimization flag '-fwhole-program' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fcaller-saves' is not supported
 // CHECK-WARNING-DAG: optimization flag '-freorder-blocks' is not supported
+// CHECK-WARNING-DAG: optimization flag '-ffat-lto-objects' is not supported
 // CHECK-WARNING-DAG: optimization flag '-fmerge-constants' is not supported
 // CHECK-WARNING-DAG: optimization flag '-finline-small-functions' is not supported
 // CHECK-WARNING-DAG: optimization flag '-ftree-dce' is not supported