[lld-macho] Add new -reproducible flag

[keith]

Summary

As of Xcode 14.3 it passes -reproducible by default to ld64. It seems
this flag was added in ld64 with Xcode 14.0, but it is not documented.
Through my testing the only thing I have seen it do is the same as
ZERO_AR_DATE, but it's possible it does more, or will do more in the
future. Since we already default to this option, this is more about
handling the command line flag to maintain Xcode compatibility than
anything else.

[int3]

Thanks!

lld/MachO/Options.td

674

try to avoid run-on sentences

lld/test/MachO/stabs.s

45–46

if ZERO_AR_DATE=1 and -reproducible is set, what does ld64 do?

[int3]

lld/test/MachO/stabs.s

45–46

nvm I got confused about which value of ZERO_AR_DATE would give us a reproducible binary. Ignore the previous comment :)

lld/MachO/Driver.cpp

for (const Arg *arg : args.filtered(OPT_ignore_auto_link_option))
     config->ignoreAutoLinkOptions.insert(arg->getValue());
   config->strictAutoLink = args.hasArg(OPT_strict_auto_link);
 
   for (const Arg *arg : args.filtered(OPT_alias)) {
     config->aliasedSymbols.push_back(
         std::make_pair(arg->getValue(0), arg->getValue(1)));
   }
 
-  // FIXME: Add a commandline flag for this too.
   if (const char *zero = getenv("ZERO_AR_DATE"))
     config->zeroModTime = strcmp(zero, "0") != 0;
+  if (args.getLastArg(OPT_reproducible))
+    config->zeroModTime = true;
 
   std::array<PlatformType, 3> encryptablePlatforms{
       PLATFORM_IOS, PLATFORM_WATCHOS, PLATFORM_TVOS};
   config->emitEncryptionInfo =
       args.hasFlag(OPT_encryptable, OPT_no_encryption,
                    is_contained(encryptablePlatforms, config->platform()));
 
 #ifndef LLVM_HAVE_LIBXAR

lld/MachO/Options.td

def v : Flag<["-"], "v">,
     HelpText<"Print the linker version and search paths in addition to linking">,
     Group<grp_rare>;
 def adhoc_codesign : Flag<["-"], "adhoc_codesign">,
     HelpText<"Write an ad-hoc code signature to the output file (default for arm64 binaries)">,
     Group<grp_rare>;
 def no_adhoc_codesign : Flag<["-"], "no_adhoc_codesign">,
     HelpText<"Do not write an ad-hoc code signature to the output file (default for x86_64 binaries)">,
     Group<grp_rare>;
+def reproducible : Flag<["-"], "reproducible">,
+    HelpText<"Make the output reproducible by removing timestamps and other non-deterministic data. This is the default behavior.">,
+    Group<grp_rare>;
 def version_details : Flag<["-"], "version_details">,
     HelpText<"Print the linker version in JSON form">,
     Flags<[HelpHidden]>,
     Group<grp_rare>;
 def no_weak_imports : Flag<["-"], "no_weak_imports">,
     HelpText<"Fail if any symbols are weak imports, allowed to be NULL at runtime">,
     Flags<[HelpHidden]>,
     Group<grp_rare>;

lld/test/MachO/stabs.s

 # RUN: (llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | \
 # RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\) \
 # RUN:       -D#TEST_TIME=0 -D#FOO_TIME=0
 # RUN: env %lld -lSystem %t/test.o %t/no-debug.o \
 # RUN:     -force_load %t/foo.a -o %t/test
 # RUN: (llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | \
 # RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.a\(foo.o\) \
 # RUN:       -D#TEST_TIME=0 -D#FOO_TIME=0
+# RUN: env ZERO_AR_DATE=0 %lld -lSystem -reproducible %t/test.o %t/foo.o \
+# RUN:     %t/no-debug.o -o %t/test
+# RUN: (llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | \
+# RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o \
+# RUN:       -D#TEST_TIME=0 -D#FOO_TIME=0
 
 ## Check that we emit absolute paths to the object files in our OSO entries
 ## even if our inputs are relative paths.
 # RUN: cd %t && ZERO_AR_DATE=0 %lld -lSystem test.o foo.o no-debug.o -o test
 # RUN: (llvm-objdump --section-headers %t/test; dsymutil -s %t/test) | \
 # RUN:   FileCheck %s -DDIR=%t -DFOO_PATH=%t/foo.o \
 # RUN:       -D#TEST_TIME=0x10 -D#FOO_TIME=0x20