[ELF, PR27091] - Implemented -t/--trace option

[grimar]

Summary

-t
--trace
Print the names of the input files as ld processes them.
This fixes https://llvm.org/bugs/show_bug.cgi?id=27091.

At first when I saw that Config->Verbose already can be used to print input file list,
I thought that there is no need to add new option, but then realized that

1. Users does not wan't to see all what Verbose prints when they want to see input files only.
2. That is consistent with gold and can be already used by someone.

So that is good option to have I think.

[emaste]

agree this is nice to have

[ruiu]

LGTM

test/ELF/trace.s

11–20

We don't care about file output order, so I wouldn't add them.

ELF/Config.h

struct Configuration {
   bool Rela;
   bool Relocatable;
   bool SaveTemps;
   bool Shared;
   bool Static = false;
   bool StripAll;
   bool SysvHash = true;
   bool Threads;
+  bool Trace;
   bool Verbose;
   bool WarnCommon;
   bool ZExecStack;
   bool ZNodelete;
   bool ZNow;
   bool ZOrigin;
   bool ZRelro;
   ELFKind EKind = ELFNoneKind;

ELF/Driver.cpp

static std::vector<MemoryBufferRef> getArchiveMembers(MemoryBufferRef MB) {
   }
   return V;
 }
 
 // Opens and parses a file. Path has to be resolved already.
 // Newly created memory buffers are owned by this driver.
 void LinkerDriver::addFile(StringRef Path) {
   using namespace llvm::sys::fs;
-  log(Path);
+  if (Config->Verbose || Config->Trace)
+    llvm::outs() << Path << "\n";
   auto MBOrErr = MemoryBuffer::getFile(Path);
   if (!MBOrErr) {
     error(MBOrErr, "cannot open " + Path);
     return;
   }
   std::unique_ptr<MemoryBuffer> &MB = *MBOrErr;
   MemoryBufferRef MBRef = MB->getMemBufferRef();
   OwningMBs.push_back(std::move(MB)); // take MB ownership
void LinkerDriver::readConfigs(opt::InputArgList &Args) {
   Config->NoinhibitExec = Args.hasArg(OPT_noinhibit_exec);
   Config->Pie = Args.hasArg(OPT_pie);
   Config->PrintGcSections = Args.hasArg(OPT_print_gc_sections);
   Config->Relocatable = Args.hasArg(OPT_relocatable);
   Config->SaveTemps = Args.hasArg(OPT_save_temps);
   Config->Shared = Args.hasArg(OPT_shared);
   Config->StripAll = Args.hasArg(OPT_strip_all);
   Config->Threads = Args.hasArg(OPT_threads);
+  Config->Trace = Args.hasArg(OPT_trace);
   Config->Verbose = Args.hasArg(OPT_verbose);
   Config->WarnCommon = Args.hasArg(OPT_warn_common);
 
   Config->DynamicLinker = getString(Args, OPT_dynamic_linker);
   Config->Entry = getString(Args, OPT_entry);
   Config->Fini = getString(Args, OPT_fini, "_fini");
   Config->Init = getString(Args, OPT_init, "_init");
   Config->OutputFile = getString(Args, OPT_o);

ELF/Options.td

 def strip_all : Flag<["--"], "strip-all">,
   HelpText<"Strip all symbols">;
 
 def sysroot : Joined<["--"], "sysroot=">,
   HelpText<"Set the system root">;
 
 def threads : Joined<["--"], "threads">;
 
+def trace: Flag<["--"], "trace">,
+  HelpText<"Print the names of the input files">;
+
 def undefined : Joined<["--"], "undefined=">,
   HelpText<"Force undefined symbol during linking">;
 
 def verbose : Flag<["--"], "verbose">;
 
 def version : Flag<["--", "-"], "version">,
   HelpText<"Display the version number">;
 

 def alias_o_output : Joined<["--"], "output=">, Alias<o>;
 def alias_pie_pic_executable: Flag<["--"], "pic-executable">, Alias<pie>;
 def alias_rpath_rpath : Joined<["-"], "rpath=">, Alias<rpath>;
 def alias_relocatable_r : Flag<["-"], "r">, Alias<relocatable>;
 def alias_shared_Bshareable : Flag<["-"], "Bshareable">, Alias<shared>;
 def alias_soname_h : JoinedOrSeparate<["-"], "h">, Alias<soname>;
 def alias_soname_soname : Separate<["-"], "soname">, Alias<soname>;
 def alias_script_T : JoinedOrSeparate<["-"], "T">, Alias<script>;
+def alias_trace : Flag<["-"], "t">, Alias<trace>;
 def alias_strip_all: Flag<["-"], "s">, Alias<strip_all>;
 def alias_undefined_u : JoinedOrSeparate<["-"], "u">, Alias<undefined>;
 def alias_wrap_wrap : Joined<["--", "-"], "wrap=">, Alias<wrap>;
 
 // Our symbol resolution algorithm handles symbols in archive files differently
 // than traditional linkers, so we don't need --start-group and --end-group.
 // These options are recongized for compatibility but ignored.
 def end_group : Flag<["--"], "end-group">;

test/ELF/trace.s

+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.foo.o
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t1.bar.o
+
+## Check -t
+# RUN: ld.lld -shared %t.foo.o -o %t.so -t 2>&1 | FileCheck %s
+# CHECK: {{.*}}.foo.o
+
+## Check --trace alias
+# RUN: ld.lld -shared %t.foo.o -o %t.so -t 2>&1 | FileCheck %s
+
+## Check output messages order (1)
+# RUN: ld.lld -shared %t.foo.o %t1.bar.o -o %t.so -t 2>&1 | FileCheck -check-prefix=ORDER1 %s
+# ORDER1: {{.*}}.foo.o
+# ORDER1: {{.*}}.bar.o
+
+## Check output messages order (2)
+# RUN: ld.lld -shared %t1.bar.o %t.foo.o -o %t.so -t 2>&1 | FileCheck -check-prefix=ORDER2 %s
+# ORDER2: {{.*}}.bar.o
+# ORDER2: {{.*}}.foo.o