[PATCH] D55717: Add --plugin-opt=emit-llvm option.

[Rui Ueyama via Phabricator via llvm-commits]

ruiu created this revision.
ruiu added reviewers: tejohnson, pcc.
Herald added subscribers: dexonsmith, steven_wu, arichardson, emaste.
Herald added a reviewer: espindola.

`--plugin-opt=emit-llvm` is an option for LTO. It makes the linker to
combine all bitcode files and write the result to an output file without
doing codegen. Gold LTO plugin has this option.

This option is being used for some post-link code analysis tools that
have to see a whole program but don't need to see them in the native
machine code.


https://reviews.llvm.org/D55717

Files:
  lld/ELF/Config.h
  lld/ELF/Driver.cpp
  lld/ELF/LTO.cpp
  lld/ELF/Options.td
  lld/test/ELF/lto/emit-llvm.ll


Index: lld/test/ELF/lto/emit-llvm.ll
===================================================================
--- /dev/null
+++ lld/test/ELF/lto/emit-llvm.ll
@@ -0,0 +1,14 @@
+; REQUIRES: x86
+
+; RUN: opt -module-hash -module-summary %s -o %t.o
+; RUN: ld.lld --plugin-opt=emit-llvm -o %t.out.o %t.o
+; RUN: llvm-dis < %t.out.o -o - | FileCheck %s
+
+; CHECK: define internal void @main()
+
+target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+define void @main() {
+  ret void
+}
Index: lld/ELF/Options.td
===================================================================
--- lld/ELF/Options.td
+++ lld/ELF/Options.td
@@ -458,6 +458,7 @@
 def: F<"plugin-opt=disable-verify">, Alias<disable_verify>, HelpText<"Alias for -disable-verify">;
 def plugin_opt_dwo_dir_eq: J<"plugin-opt=dwo_dir=">,
   HelpText<"Directory to store .dwo files when LTO and debug fission are used">;
+def plugin_opt_emit_llvm: F<"plugin-opt=emit-llvm">;
 def: J<"plugin-opt=jobs=">, Alias<thinlto_jobs>, HelpText<"Alias for -thinlto-jobs">;
 def: J<"plugin-opt=lto-partitions=">, Alias<lto_partitions>, HelpText<"Alias for -lto-partitions">;
 def plugin_opt_mcpu_eq: J<"plugin-opt=mcpu=">;
Index: lld/ELF/LTO.cpp
===================================================================
--- lld/ELF/LTO.cpp
+++ lld/ELF/LTO.cpp
@@ -103,6 +103,14 @@
   C.DebugPassManager = Config->LTODebugPassManager;
   C.DwoDir = Config->DwoDir;
 
+  if (Config->EmitLLVM) {
+    C.PostInternalizeModuleHook = [](size_t Task, const Module &M) {
+      if (std::unique_ptr<raw_fd_ostream> OS = openFile(Config->OutputFile))
+        WriteBitcodeToFile(M, *OS, false);
+      return false;
+    };
+  }
+
   if (Config->SaveTemps)
     checkError(C.addSaveTemps(Config->OutputFile.str() + ".",
                               /*UseInputModulePath*/ true));
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -776,6 +776,7 @@
   Config->DynamicLinker = getDynamicLinker(Args);
   Config->EhFrameHdr =
       Args.hasFlag(OPT_eh_frame_hdr, OPT_no_eh_frame_hdr, false);
+  Config->EmitLLVM = Args.hasArg(OPT_plugin_opt_emit_llvm, false);
   Config->EmitRelocs = Args.hasArg(OPT_emit_relocs);
   Config->CallGraphProfileSort = Args.hasFlag(
       OPT_call_graph_profile_sort, OPT_no_call_graph_profile_sort, true);
@@ -1581,6 +1582,12 @@
   if (Config->ThinLTOIndexOnly)
     return;
 
+  // Likewise, --plugin-opt=emit-llvm is an option to make LTO create
+  // an output file in bitcode and exit, so that you can just get a
+  // combined bitcode file.
+  if (Config->EmitLLVM)
+    return;
+
   // Apply symbol renames for -wrap.
   if (!Wrapped.empty())
     wrapSymbols<ELFT>(Wrapped);
Index: lld/ELF/Config.h
===================================================================
--- lld/ELF/Config.h
+++ lld/ELF/Config.h
@@ -135,6 +135,7 @@
   bool Demangle = true;
   bool DisableVerify;
   bool EhFrameHdr;
+  bool EmitLLVM;
   bool EmitRelocs;
   bool EnableNewDtags;
   bool ExecuteOnly;


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