[COFF] added support for /lldsavetemps

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

Reviewers: ruiu, pcc

Reviewed By: ruiu, pcc

Subscribers: mehdi_amini

Differential Revision: https://reviews.llvm.org/D29518

llvm-svn: 294498

Author: inglorion

lld/COFF/Config.h

@@ -105,6 +105,8 @@ struct Configuration {
   std::map<std::string, int> DLLOrder;
   SymbolBody *DelayLoadHelper = nullptr;
 
+  bool SaveTemps = false;
+
   // Used for SafeSEH.
   Symbol *SEHTable = nullptr;
   Symbol *SEHCount = nullptr;

lld/COFF/Driver.cpp

@@ -622,6 +622,10 @@ void LinkerDriver::link(ArrayRef<const char *> ArgsArr) {
     }
   }
 
+  // Handle /lldsavetemps
+  if (Args.hasArg(OPT_lldsavetemps))
+    Config->SaveTemps = true;
+
   // Handle /failifmismatch
   for (auto *Arg : Args.filtered(OPT_failifmismatch))
     checkFailIfMismatch(Arg->getValue());

lld/COFF/LTO.cpp

@@ -54,13 +54,24 @@ static void checkError(Error E) {
   });
 }
 
+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);
@@ -116,8 +127,16 @@ std::vector<StringRef> BitcodeCompiler::compile() {
   }));
 
   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");
+    }
+    Ret.emplace_back(Buff[I].data(), Buff[I].size());
+  }
   return Ret;
 }

lld/COFF/Options.td

@@ -28,6 +28,8 @@ 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">;

lld/test/COFF/savetemps.ll

@@ -0,0 +1,24 @@
+; 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
+}