[COFF] added support for /lldsavetemps

[inglorion]

Summary

This adds an option to save temporary files generated during link-time optimization. This can be useful for debugging.

[ruiu]

Can you add a test?

COFF/Driver.cpp

619–622 ↗

(On Diff #87038)

You want to move this code outside of this for loop because this loop is for /opt. Handle this just like /implib.

[inglorion]

COFF/Driver.cpp

619–622 ↗

(On Diff #87038)

I'll be happy to do that. I actually put it under /opt on purpose so as not to conflict with any other options we might want to add in the future. I suppose the "lld" prefix guards against that well enough.

[pcc]

Should this also write the object files like the ELF linker does?

[inglorion]

• Made /lldsavetemps a top-level option instead of nesting it under /opt.
• Also save object files.
• Added test.

[inglorion]

update revision title

[ruiu]

COFF/Driver.cpp

625 ↗

(On Diff #87527)

Since other chunks of code has comments, add the same comment.

// Handle /lldsavetemps

COFF/LTO.cpp

61 ↗

(On Diff #87527)

Do we have error() in COFF? I think you want to use fatal().

[inglorion]

COFF/LTO.cpp

61 ↗

(On Diff #87527)

We do. I'm also working on a patch to make the error limit configurable.

[inglorion]

added comment

[pcc]

LGTM if Rui's happy with it.

[ruiu]

LGTM

[ruiu]

LGTM

lld/trunk/COFF/Config.h

struct Configuration {
   // True if we are creating a DLL.
   bool DLL = false;
   StringRef Implib;
   std::vector<Export> Exports;
   std::set<std::string> DelayLoads;
   std::map<std::string, int> DLLOrder;
   SymbolBody *DelayLoadHelper = nullptr;
 
+  bool SaveTemps = false;
+
   // Used for SafeSEH.
   Symbol *SEHTable = nullptr;
   Symbol *SEHCount = nullptr;
 
   // Used for /opt:lldlto=N
   unsigned LTOOptLevel = 2;
 
   // Used for /opt:lldltojobs=N

lld/trunk/COFF/Driver.cpp

for (StringRef S : Vec) {
           fatal("/opt:lldltopartitions: invalid partition count: " + N);
         continue;
       }
       if (S != "ref" && S != "lbr" && S != "nolbr")
         fatal("/opt: unknown option: " + S);
     }
   }
 
+  // Handle /lldsavetemps
+  if (Args.hasArg(OPT_lldsavetemps))
+    Config->SaveTemps = true;
+
   // Handle /failifmismatch
   for (auto *Arg : Args.filtered(OPT_failifmismatch))
     checkFailIfMismatch(Arg->getValue());
 
   // Handle /merge
   for (auto *Arg : Args.filtered(OPT_merge))
     parseMerge(Arg->getValue());
 

lld/trunk/COFF/LTO.cpp

 
 static void checkError(Error E) {
   handleAllErrors(std::move(E), [&](ErrorInfoBase &EIB) -> Error {
     error(EIB.message());
     return Error::success();
   });
 }
 
+static void saveBuffer(StringRef Buffer, const Twine &Path) {
+  std::error_code EC;
+  raw_fd_ostream OS(Path.str(), EC, sys::fs::OpenFlags::F_None);
+  if (EC)
+    error("cannot create " + Path + ": " + EC.message());
+  OS << Buffer;
+}
+
 static std::unique_ptr<lto::LTO> createLTO() {
   lto::Config Conf;
   Conf.Options = InitTargetOptionsFromCodeGenFlags();
   Conf.RelocModel = Reloc::PIC_;
   Conf.DisableVerify = true;
   Conf.DiagHandler = diagnosticHandler;
   Conf.OptLevel = Config->LTOOptLevel;
+  if (Config->SaveTemps)
+    checkError(Conf.addSaveTemps(std::string(Config->OutputFile) + ".",
+                                 /*UseInputModulePath*/ true));
   lto::ThinBackend Backend;
   if (Config->LTOJobs != -1u)
     Backend = lto::createInProcessThinBackend(Config->LTOJobs);
   return llvm::make_unique<lto::LTO>(std::move(Conf), Backend,
                                      Config->LTOPartitions);
 }
 
 BitcodeCompiler::BitcodeCompiler() : LTOObj(createLTO()) {}
std::vector<StringRef> BitcodeCompiler::compile() {
   Buff.resize(MaxTasks);
 
   checkError(LTOObj->run([&](size_t Task) {
     return llvm::make_unique<lto::NativeObjectStream>(
         llvm::make_unique<raw_svector_ostream>(Buff[Task]));
   }));
 
   std::vector<StringRef> Ret;
-  for (unsigned I = 0; I != MaxTasks; ++I)
-    if (!Buff[I].empty())
-      Ret.emplace_back(Buff[I].data(), Buff[I].size());
+  for (unsigned I = 0; I != MaxTasks; ++I) {
+    if (Buff[I].empty())
+      continue;
+    if (Config->SaveTemps) {
+      if (I == 0)
+        saveBuffer(Buff[I], Config->OutputFile + ".lto.obj");
+      else
+        saveBuffer(Buff[I], Config->OutputFile + Twine(I) + ".lto.obj");
+    }
+  }
   return Ret;
 }

lld/trunk/COFF/Options.td

 def entry   : P<"entry", "Name of entry point symbol">;
 def export  : P<"export", "Export a function">;
 // No help text because /failifmismatch is not intended to be used by the user.
 def failifmismatch : P<"failifmismatch", "">;
 def heap    : P<"heap", "Size of the heap">;
 def implib  : P<"implib", "Import library name">;
 def libpath : P<"libpath", "Additional library search path">;
 def linkrepro : P<"linkrepro", "Dump linker invocation and input files for debugging">;
+def lldsavetemps : F<"lldsavetemps">,
+    HelpText<"Save temporary files instead of deleting them">;
 def machine : P<"machine", "Specify target platform">;
 def merge   : P<"merge", "Combine sections">;
 def mllvm   : P<"mllvm", "Options to pass to LLVM">;
 def nodefaultlib : P<"nodefaultlib", "Remove a default library">;
 def opt     : P<"opt", "Control optimizations">;
 def out     : P<"out", "Path to file to write output">;
 def pdb : P<"pdb", "PDB file path">;
 def section : P<"section", "Specify section attributes">;

lld/trunk/test/COFF/savetemps.ll

+; RUN: rm -f %T/savetemps.*
+; RUN: llvm-as -o %T/savetemps.obj %s
+; RUN: lld-link /out:%T/savetemps.exe /entry:main /subsystem:console %T/savetemps.obj
+; RUN: not llvm-dis -o - %T/savetemps.exe.0.0.preopt.bc
+; RUN: not llvm-dis -o - %T/savetemps.exe.0.2.internalize.bc
+; RUN: not llvm-dis -o - %T/savetemps.exe.0.4.opt.bc
+; RUN: not llvm-dis -o - %T/savetemps.exe.0.5.precodegen.bc
+; RUN: not llvm-objdump -s %T/savetemps.exe.lto.obj
+; RUN: lld-link /lldsavetemps /out:%T/savetemps.exe /entry:main /subsystem:console %T/savetemps.obj
+; RUN: llvm-dis -o - %T/savetemps.exe.0.0.preopt.bc | FileCheck %s
+; RUN: llvm-dis -o - %T/savetemps.exe.0.2.internalize.bc | FileCheck %s
+; RUN: llvm-dis -o - %T/savetemps.exe.0.4.opt.bc | FileCheck %s
+; RUN: llvm-dis -o - %T/savetemps.exe.0.5.precodegen.bc | FileCheck %s
+; RUN: llvm-objdump -s %T/savetemps.exe.lto.obj | FileCheck --check-prefix=CHECK-OBJDUMP %s
+
+; CHECK: define i32 @main()
+; CHECK-OBJDUMP: file format COFF
+
+target datalayout = "e-m:w-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-pc-windows-msvc"
+
+define i32 @main() {
+  ret i32 0
+}