[Driver][MachineOutliner] Support outlining option with LTO

[yroux]

Summary

This patch propagates the -moutline flag when LTO is enabled and avoids passing it explicitly to the linker plugin.

[yroux]

ping

[paquette]

LGTM

clang/lib/Driver/ToolChains/Clang.cpp

   if (Args.hasFlag(options::OPT_fcomplete_member_pointers,
                    options::OPT_fno_complete_member_pointers, false))
     CmdArgs.push_back("-fcomplete-member-pointers");
 
   if (!Args.hasFlag(options::OPT_fcxx_static_destructors,
                     options::OPT_fno_cxx_static_destructors, true))
     CmdArgs.push_back("-fno-c++-static-destructors");
 
-  if (Arg *A = Args.getLastArg(options::OPT_moutline,
-                               options::OPT_mno_outline)) {
-    if (A->getOption().matches(options::OPT_moutline)) {
-      // We only support -moutline in AArch64 and ARM targets right now. If
-      // we're not compiling for these, emit a warning and ignore the flag.
-      // Otherwise, add the proper mllvm flags.
-      if (!(Triple.isARM() || Triple.isThumb() ||
-            Triple.getArch() == llvm::Triple::aarch64 ||
-            Triple.getArch() == llvm::Triple::aarch64_32)) {
-        D.Diag(diag::warn_drv_moutline_unsupported_opt) << Triple.getArchName();
-      } else {
-        CmdArgs.push_back("-mllvm");
-        CmdArgs.push_back("-enable-machine-outliner");
-      }
-    } else {
-      // Disable all outlining behaviour.
-      CmdArgs.push_back("-mllvm");
-      CmdArgs.push_back("-enable-machine-outliner=never");
-    }
-  }
+  addMachineOutlinerArgs(D, Args, CmdArgs, Triple, /*IsLTO=*/false);
 
   if (Arg *A = Args.getLastArg(options::OPT_moutline_atomics,
                                options::OPT_mno_outline_atomics)) {
     if (A->getOption().matches(options::OPT_moutline_atomics)) {
       // Option -moutline-atomics supported for AArch64 target only.
       if (!Triple.isAArch64()) {
         D.Diag(diag::warn_drv_moutline_atomics_unsupported_opt)
             << Triple.getArchName();

clang/lib/Driver/ToolChains/CommonArgs.h

void addMultilibFlag(bool Enabled, const char *const Flag,
                      Multilib::flags_list &Flags);
 
 void addX86AlignBranchArgs(const Driver &D, const llvm::opt::ArgList &Args,
                            llvm::opt::ArgStringList &CmdArgs, bool IsLTO);
 
 unsigned getOrCheckAMDGPUCodeObjectVersion(const Driver &D,
                                            const llvm::opt::ArgList &Args,
                                            bool Diagnose = false);
+
+void addMachineOutlinerArgs(const Driver &D, const llvm::opt::ArgList &Args,
+                            llvm::opt::ArgStringList &CmdArgs,
+                            const llvm::Triple &Triple, bool IsLTO);
 } // end namespace tools
 } // end namespace driver
 } // end namespace clang
 
 #endif // LLVM_CLANG_LIB_DRIVER_TOOLCHAINS_COMMONARGS_H

clang/lib/Driver/ToolChains/CommonArgs.cpp

#endif
   // Handle serialized remarks options: '-fsave-optimization-record'
   // and '-foptimization-record-*'.
   if (willEmitRemarks(Args))
     renderRemarksOptions(Args, CmdArgs, ToolChain.getEffectiveTriple(), Input,
                          Output);
 
   // Handle remarks hotness/threshold related options.
   renderRemarksHotnessOptions(Args, CmdArgs);
+
+  addMachineOutlinerArgs(D, Args, CmdArgs, ToolChain.getEffectiveTriple(),
+                         /*IsLTO=*/true);
 }
 
 void tools::addArchSpecificRPath(const ToolChain &TC, const ArgList &Args,
                                  ArgStringList &CmdArgs) {
   // Enable -frtlib-add-rpath by default for the case of VE.
   const bool IsVE = TC.getTriple().isVE();
   bool DefaultValue = IsVE;
   if (!Args.hasFlag(options::OPT_frtlib_add_rpath,
if (CodeObjArg->getOption().getID() ==
       if (Diagnose &&
           (Remnant || CodeObjVer < MinCodeObjVer || CodeObjVer > MaxCodeObjVer))
         D.Diag(diag::err_drv_invalid_int_value)
             << CodeObjArg->getAsString(Args) << CodeObjArg->getValue();
     }
   }
   return CodeObjVer;
 }
+
+void tools::addMachineOutlinerArgs(const Driver &D,
+                                   const llvm::opt::ArgList &Args,
+                                   llvm::opt::ArgStringList &CmdArgs,
+                                   const llvm::Triple &Triple, bool IsLTO) {
+  auto addArg = [&, IsLTO](const Twine &Arg) {
+    if (IsLTO) {
+      CmdArgs.push_back(Args.MakeArgString("-plugin-opt=" + Arg));
+    } else {
+      CmdArgs.push_back("-mllvm");
+      CmdArgs.push_back(Args.MakeArgString(Arg));
+    }
+  };
+
+  if (Arg *A = Args.getLastArg(options::OPT_moutline,
+                               options::OPT_mno_outline)) {
+    if (A->getOption().matches(options::OPT_moutline)) {
+      // We only support -moutline in AArch64 and ARM targets right now. If
+      // we're not compiling for these, emit a warning and ignore the flag.
+      // Otherwise, add the proper mllvm flags.
+      if (!(Triple.isARM() || Triple.isThumb() ||
+            Triple.getArch() == llvm::Triple::aarch64 ||
+            Triple.getArch() == llvm::Triple::aarch64_32)) {
+        D.Diag(diag::warn_drv_moutline_unsupported_opt) << Triple.getArchName();
+      } else {
+        addArg(Twine("-enable-machine-outliner"));
+      }
+    } else {
+      // Disable all outlining behaviour.
+      addArg(Twine("-enable-machine-outliner=never"));
+    }
+  }
+}

clang/test/Driver/arm-machine-outliner.c

+// REQUIRES: arm-registered-target
+// RUN: %clang -target armv7-linux-gnueabihf -moutline -c %s -### 2>&1 | FileCheck %s -check-prefix=ON
+// ON: "-mllvm" "-enable-machine-outliner"
+// RUN: %clang -target armv7-linux-gnueabihf -flto -moutline %s -### 2>&1 | FileCheck %s -check-prefix=ON-LTO
+// ON-LTO: "-plugin-opt=-enable-machine-outliner"
+// RUN: %clang -target armv7-linux-gnueabihf -moutline -mno-outline -c %s -### 2>&1 | FileCheck %s -check-prefix=OFF
+// OFF: "-mllvm" "-enable-machine-outliner=never"
+// RUN: %clang -target armv7-linux-gnueabihf -flto -moutline -mno-outline %s -### 2>&1 | FileCheck %s -check-prefix=OFF-LTO
+// OFF-LTO: "-plugin-opt=-enable-machine-outliner=never"