[clang] - Simplify tools::SplitDebugName.

[grimar]

Summary

This should be NFC change.

SplitDebugName started to accept the Output that
can be used to simplify the logic a bit, also it
seems that code in SplitDebugName that uses
OPT_fdebug_compilation_dir is simply dead.

My understanding may be wrong because I am
not very familiar with clang, but I investigated this and
below in the comment, there are my
arguments for that.

[grimar]

SplitDebugName is called from the following 4 places:

1) void Clang::ConstructJob()
(https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Clang.cpp#L3933)

We can get here when clang construct jobs for regular case (cpp files):

EX: main.cpp -g -gsplit-dwarf  -o ooo

Clang by itself does not recognize the '-fdebug-compilation-dir':

clang main.cpp -g -gsplit-dwarf  -o ooo -### -fdebug-compilation-dir
clang-8: error: unknown argument: '-fdebug-compilation-dir'

So I believe this option can not be used, be in Args
and hence affect on anything during this flow.

In other places clang constructs assembly jobs:

2) void ClangAs::ConstructJob()
(https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Clang.cpp#L5900)

Here it tries to use the OPT_fdebug_compilation_dir option from Args:
https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/CommonArgs.cpp#L824

And this is used to construct the argument for -split-dwarf-file.

The following also would not work:

clang main.s -g -gsplit-dwarf  -o ooo -fdebug-compilation-dir,xxx
clang-8: error: unknown argument: '-fdebug-compilation-dir,xxx'

So I do not see the way to add the -debug-compilation-dir to Args here too,
so SplitDebugName does not use the -fdebug-compilation-dir I think
and its logic is dead for this case too I believe)

3, 4) These 2 are similar:

tools::gnutools::Assembler::ConstructJob()
(https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Gnu.cpp#L820)

tools::MinGW::Assembler::ConstructJob()
https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/MinGW.cpp#L57

Both call SplitDebugName to construct calls for objcopy:
https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/CommonArgs.cpp#L833

But again, Args for their ConstructJob seems can never contain the -fdebug-compilation-dir
I just do not see any way to achieve that.

Clang's code adds the -fdebug-compilation-dir by itself in Clang::ConstructJob() and
ClangAs::ConstructJob(), but it will never be used in SplitDebugName I think:
https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Clang.cpp#L601
https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Clang.cpp#L5795
https://github.com/llvm-mirror/clang/blob/master/lib/Driver/ToolChains/Clang.cpp#L4172

That -fdebug-compilation-dir is used in other places, not in the SplitDebugName
(used in invocations for -cc1 and -cc1as:
https://github.com/llvm-mirror/clang/blob/master/tools/driver/cc1as_main.cpp#L234
https://github.com/llvm-mirror/clang/blob/master/lib/Frontend/CompilerInvocation.cpp#L944)

After changes done by this patch, no check-llvm/check-clang tests started to fail for me.

[dblaikie]

Agreed - looks like this went in untested in r175813 & has never been used.

cfe/trunk/lib/Driver/ToolChains/Clang.cpp

#endif
   // can propagate it to the backend.
   bool SplitDWARF = (DwarfFission != DwarfFissionKind::None) &&
                     (RawTriple.isOSLinux() || RawTriple.isOSFuchsia()) &&
                     (isa<AssembleJobAction>(JA) || isa<CompileJobAction>(JA) ||
                      isa<BackendJobAction>(JA));
   const char *SplitDWARFOut;
   if (SplitDWARF) {
     CmdArgs.push_back("-split-dwarf-file");
-    SplitDWARFOut = SplitDebugName(Args, Input, Output);
+    SplitDWARFOut = SplitDebugName(Args, Output);
     CmdArgs.push_back(SplitDWARFOut);
   }
 
   // Pass the linker version in use.
   if (Arg *A = Args.getLastArg(options::OPT_mlinker_version_EQ)) {
     CmdArgs.push_back("-target-linker-version");
     CmdArgs.push_back(A->getValue());
   }
void ClangAs::ConstructJob(Compilation &C, const JobAction &JA,
   CmdArgs.push_back("-o");
   CmdArgs.push_back(Output.getFilename());
 
   const llvm::Triple &T = getToolChain().getTriple();
   Arg *A;
   if ((getDebugFissionKind(D, Args, A) == DwarfFissionKind::Split) &&
       (T.isOSLinux() || T.isOSFuchsia())) {
     CmdArgs.push_back("-split-dwarf-file");
-    CmdArgs.push_back(SplitDebugName(Args, Input, Output));
+    CmdArgs.push_back(SplitDebugName(Args, Output));
   }
 
   assert(Input.isFilename() && "Invalid input.");
   CmdArgs.push_back(Input.getFilename());
 
   const char *Exec = getToolChain().getDriver().getClangProgramPath();
   C.addCommand(llvm::make_unique<Command>(JA, *this, Exec, CmdArgs, Inputs));
 }

cfe/trunk/lib/Driver/ToolChains/CommonArgs.h

 
 void AddHIPLinkerScript(const ToolChain &TC, Compilation &C,
                         const InputInfo &Output, const InputInfoList &Inputs,
                         const llvm::opt::ArgList &Args,
                         llvm::opt::ArgStringList &CmdArgs, const JobAction &JA,
                         const Tool &T);
 
 const char *SplitDebugName(const llvm::opt::ArgList &Args,
-                           const InputInfo &Input, const InputInfo &Output);
+                           const InputInfo &Output);
 
 void SplitDebugInfo(const ToolChain &TC, Compilation &C, const Tool &T,
                     const JobAction &JA, const llvm::opt::ArgList &Args,
                     const InputInfo &Output, const char *OutFile);
 
 void AddGoldPlugin(const ToolChain &ToolChain, const llvm::opt::ArgList &Args,
                    llvm::opt::ArgStringList &CmdArgs, const InputInfo &Output,
                    const InputInfo &Input, bool IsThinLTO);

cfe/trunk/lib/Driver/ToolChains/CommonArgs.cpp

 bool tools::areOptimizationsEnabled(const ArgList &Args) {
   // Find the last -O arg and see if it is non-zero.
   if (Arg *A = Args.getLastArg(options::OPT_O_Group))
     return !A->getOption().matches(options::OPT_O0);
   // Defaults to -O0.
   return false;
 }
 
-const char *tools::SplitDebugName(const ArgList &Args, const InputInfo &Input,
+const char *tools::SplitDebugName(const ArgList &Args,
                                   const InputInfo &Output) {
   if (Arg *A = Args.getLastArg(options::OPT_gsplit_dwarf_EQ))
     if (StringRef(A->getValue()) == "single")
       return Args.MakeArgString(Output.getFilename());
 
-  Arg *FinalOutput = Args.getLastArg(options::OPT_o);
-  if (FinalOutput && Args.hasArg(options::OPT_c)) {
-    SmallString<128> T(FinalOutput->getValue());
-    llvm::sys::path::replace_extension(T, "dwo");
-    return Args.MakeArgString(T);
-  } else {
-    // Use the compilation dir.
-    SmallString<128> T(
-        Args.getLastArgValue(options::OPT_fdebug_compilation_dir));
-    SmallString<128> F(llvm::sys::path::stem(Input.getBaseInput()));
-    llvm::sys::path::replace_extension(F, "dwo");
-    T += F;
-    return Args.MakeArgString(F);
-  }
+  SmallString<128> T(Output.getFilename());
 }
 
 void tools::SplitDebugInfo(const ToolChain &TC, Compilation &C, const Tool &T,
                            const JobAction &JA, const ArgList &Args,
                            const InputInfo &Output, const char *OutFile) {
   ArgStringList ExtractArgs;
   ExtractArgs.push_back("--extract-dwo");
 

cfe/trunk/lib/Driver/ToolChains/Gnu.cpp

void tools::gnutools::Assembler::ConstructJob(Compilation &C,
   C.addCommand(llvm::make_unique<Command>(JA, *this, Exec, CmdArgs, Inputs));
 
   // Handle the debug info splitting at object creation time if we're
   // creating an object.
   // TODO: Currently only works on linux with newer objcopy.
   if (Args.hasArg(options::OPT_gsplit_dwarf) &&
       getToolChain().getTriple().isOSLinux())
     SplitDebugInfo(getToolChain(), C, *this, JA, Args, Output,
-                   SplitDebugName(Args, Inputs[0], Output));
+                   SplitDebugName(Args, Output));
 }
 
 namespace {
 // Filter to remove Multilibs that don't exist as a suffix to Path
 class FilterNonExistent {
   StringRef Base, File;
   llvm::vfs::FileSystem &VFS;
 

cfe/trunk/lib/Driver/ToolChains/MinGW.cpp

void tools::MinGW::Assembler::ConstructJob(Compilation &C, const JobAction &JA,
   for (const auto &II : Inputs)
     CmdArgs.push_back(II.getFilename());
 
   const char *Exec = Args.MakeArgString(getToolChain().GetProgramPath("as"));
   C.addCommand(llvm::make_unique<Command>(JA, *this, Exec, CmdArgs, Inputs));
 
   if (Args.hasArg(options::OPT_gsplit_dwarf))
     SplitDebugInfo(getToolChain(), C, *this, JA, Args, Output,
-                   SplitDebugName(Args, Inputs[0], Output));
+                   SplitDebugName(Args, Output));
 }
 
 void tools::MinGW::Linker::AddLibGCC(const ArgList &Args,
                                      ArgStringList &CmdArgs) const {
   if (Args.hasArg(options::OPT_mthreads))
     CmdArgs.push_back("-lmingwthrd");
   CmdArgs.push_back("-lmingw32");