Print out "Alias for -foo" instead of repeating the same help message for -foo.

[ruiu]

Summary

Since aliases don't actually need name, so I removed it from Options.td
to keep the definitions concise.

Before:

-(                      Ignored for compatibility with GNU unless you pass --warn-backrefs
-)                      Ignored for compatibility with GNU unless you pass --warn-backrefs
--allow-multiple-definition Allow multiple definitions
--apply-dynamic-relocs  Apply dynamic relocations to place
--as-needed             Only set DT_NEEDED for shared libraries if used
--auxiliary=<value>     Set DT_AUXILIARY field to the specified name
--Bdynamic              Link against shared libraries
--Bshareable            Build a shared object
...

After:

-(                      Alias for --start-group
-)                      Alias for --end-group
--allow-multiple-definition Allow multiple definitions
--apply-dynamic-relocs  Apply dynamic relocations to place
--as-needed             Only set DT_NEEDED for shared libraries if used
--auxiliary=<value>     Set DT_AUXILIARY field to the specified name
--Bdynamic              Link against shared libraries (default)
--Bshareable            Alias for --shared
...

[pcc]

LGTM

[bd1976llvm]

Hi Rui,

I made a mistake when writing out the help text for one of our aliased options (local to our downstream port of lld) whilst merging in this change. It would be nice if we didn't have to write out the help text for aliased options.

I suggest:

• We change OptTable::PrintHelp[lvm\lib\Option\OptTable.cpp] to take an additional parameter that specifies the behaviour when no help text has been specified for an aliased option:
  1. Copy the help text from the aliased option
  2. Print "Alias for " + Alias.getPrefixedName ()
• We remove help text for all aliased options in lld and specify behaviour 2. above when creating our options parser.

What do you think?

[ruiu]

I would probably prefer this dumb but simple change over making a change to OptTable.cpp so that it synthesizes "Alias for ..." strings for alias options. If we have hundreds of lines of aliases, that might help, but for this 30+ options, maybe it's a bit too much?

lld/ELF/Options.td

 
 defm wrap: Eq<"wrap", "Use wrapper functions for symbol">,
   MetaVarName<"<symbol>">;
 
 def z: JoinedOrSeparate<["-"], "z">, MetaVarName<"<option>">,
   HelpText<"Linker option extensions">;
 
 // Aliases
-def alias_auxiliary: Separate<["-"], "f">, Alias<auxiliary>;
-def alias_Bdynamic_call_shared: F<"call_shared">, Alias<Bdynamic>;
-def alias_Bdynamic_dy: F<"dy">, Alias<Bdynamic>;
-def alias_Bstatic_dn: F<"dn">, Alias<Bstatic>;
-def alias_Bstatic_non_shared: F<"non_shared">, Alias<Bstatic>;
-def alias_Bstatic_static: F<"static">, Alias<Bstatic>;
-def alias_define_common_d: Flag<["-"], "d">, Alias<define_common>;
-def alias_define_common_dc: F<"dc">, Alias<define_common>;
-def alias_define_common_dp: F<"dp">, Alias<define_common>;
-def alias_discard_all_x: Flag<["-"], "x">, Alias<discard_all>;
-def alias_discard_locals_X: Flag<["-"], "X">, Alias<discard_locals>;
-def alias_emit_relocs: Flag<["-"], "q">, Alias<emit_relocs>;
-def alias_end_group_paren: Flag<["-"], ")">, Alias<end_group>;
-def alias_entry_e: JoinedOrSeparate<["-"], "e">, Alias<entry>;
-def alias_export_dynamic_E: Flag<["-"], "E">, Alias<export_dynamic>;
-def alias_filter: Separate<["-"], "F">, Alias<filter>;
-def alias_format_b: Separate<["-"], "b">, Alias<format>;
-def alias_library: JoinedOrSeparate<["-"], "l">, Alias<library>;
-def alias_library_path: JoinedOrSeparate<["-"], "L">, Alias<library_path>;
-def alias_no_pie_pic_executable: F<"no-pic-executable">, Alias<no_pie>;
-def alias_omagic: Flag<["-"], "N">, Alias<omagic>;
-def alias_o_output: Joined<["--"], "output=">, Alias<o>;
-def alias_o_output2 : Separate<["--"], "output">, Alias<o>;
-def alias_pie_pic_executable: F<"pic-executable">, Alias<pie>;
-def alias_print_map_M: Flag<["-"], "M">, Alias<print_map>;
-def alias_relocatable_r: Flag<["-"], "r">, Alias<relocatable>;
-def alias_rpath_R: JoinedOrSeparate<["-"], "R">, Alias<rpath>;
-def alias_script_T: JoinedOrSeparate<["-"], "T">, Alias<script>;
-def alias_shared_Bshareable: F<"Bshareable">, Alias<shared>;
-def alias_soname_h: JoinedOrSeparate<["-"], "h">, Alias<soname>;
-def alias_start_group_paren: Flag<["-"], "(">, Alias<start_group>;
-def alias_strip_all: Flag<["-"], "s">, Alias<strip_all>;
-def alias_strip_debug_S: Flag<["-"], "S">, Alias<strip_debug>;
-def alias_trace: Flag<["-"], "t">, Alias<trace>;
-def alias_trace_symbol_y : JoinedOrSeparate<["-"], "y">, Alias<trace_symbol>;
-def alias_Ttext_segment: Separate<["-", "--"], "Ttext-segment">, Alias<Ttext>;
-def alias_Ttext_segment_eq: Joined<["-", "--"], "Ttext-segment=">, Alias<Ttext>;
-def alias_undefined_u: JoinedOrSeparate<["-"], "u">, Alias<undefined>;
-def alias_version_V: Flag<["-"], "V">, Alias<version>;
+def: Separate<["-"], "f">, Alias<auxiliary>, HelpText<"Alias for --auxiliary">;
+def: F<"call_shared">, Alias<Bdynamic>, HelpText<"Alias for --Bdynamic">;
+def: F<"dy">, Alias<Bdynamic>, HelpText<"Alias for --Bdynamic">;
+def: F<"dn">, Alias<Bstatic>, HelpText<"Alias for --Bstatic">;
+def: F<"non_shared">, Alias<Bstatic>, HelpText<"Alias for --Bstatic">;
+def: F<"static">, Alias<Bstatic>, HelpText<"Alias for --Bstatic">;
+def: Flag<["-"], "d">, Alias<define_common>, HelpText<"Alias for --define-common">;
+def: F<"dc">, Alias<define_common>, HelpText<"Alias for --define-common">;
+def: F<"dp">, Alias<define_common>, HelpText<"Alias for --define-common">;
+def: Flag<["-"], "x">, Alias<discard_all>, HelpText<"Alias for --discard-all">;
+def: Flag<["-"], "X">, Alias<discard_locals>, HelpText<"Alias for --discard-locals">;
+def: Flag<["-"], "q">, Alias<emit_relocs>, HelpText<"Alias for --emit-relocs">;
+def: Flag<["-"], ")">, Alias<end_group>, HelpText<"Alias for --end-group">;
+def: JoinedOrSeparate<["-"], "e">, Alias<entry>, HelpText<"Alias for --entry">;
+def: Flag<["-"], "E">, Alias<export_dynamic>, HelpText<"Alias for --export-dynamic">;
+def: Separate<["-"], "F">, Alias<filter>, HelpText<"Alias for --filter">;
+def: Separate<["-"], "b">, Alias<format>, HelpText<"Alias for --format">;
+def: JoinedOrSeparate<["-"], "l">, Alias<library>, HelpText<"Alias for --library">;
+def: JoinedOrSeparate<["-"], "L">, Alias<library_path>, HelpText<"Alias for --library-path">;
+def: F<"no-pic-executable">, Alias<no_pie>, HelpText<"Alias for --no-pie">;
+def: Flag<["-"], "N">, Alias<omagic>, HelpText<"Alias for --omagic">;
+def: Joined<["--"], "output=">, Alias<o>, HelpText<"Alias for -o">;
+def: Separate<["--"], "output">, Alias<o>, HelpText<"Alias for -o">;
+def: F<"pic-executable">, Alias<pie>, HelpText<"Alias for --pie">;
+def: Flag<["-"], "M">, Alias<print_map>, HelpText<"Alias for --print-map">;
+def: Flag<["-"], "r">, Alias<relocatable>, HelpText<"Alias for --relocatable">;
+def: JoinedOrSeparate<["-"], "R">, Alias<rpath>, HelpText<"Alias for --rpath">;
+def: JoinedOrSeparate<["-"], "T">, Alias<script>, HelpText<"Alias for --script">;
+def: F<"Bshareable">, Alias<shared>, HelpText<"Alias for --shared">;
+def: JoinedOrSeparate<["-"], "h">, Alias<soname>, HelpText<"Alias for --soname">;
+def: Flag<["-"], "(">, Alias<start_group>, HelpText<"Alias for --start-group">;
+def: Flag<["-"], "s">, Alias<strip_all>, HelpText<"Alias for --strip-all">;
+def: Flag<["-"], "S">, Alias<strip_debug>, HelpText<"Alias for --strip-debug">;
+def: Flag<["-"], "t">, Alias<trace>, HelpText<"Alias for --trace">;
+def: JoinedOrSeparate<["-"], "y">, Alias<trace_symbol>, HelpText<"Alias for --trace-symbol">;
+def: Separate<["-", "--"], "Ttext-segment">, Alias<Ttext>, HelpText<"Alias for --Ttext">;
+def: Joined<["-", "--"], "Ttext-segment=">, Alias<Ttext>, HelpText<"Alias for --Ttext">;
+def: JoinedOrSeparate<["-"], "u">, Alias<undefined>, HelpText<"Alias for --undefined">;
+def: Flag<["-"], "V">, Alias<version>, HelpText<"Alias for --version">;
 
 // LTO-related options.
 def lto_aa_pipeline: J<"lto-aa-pipeline=">,
   HelpText<"AA pipeline to run during LTO. Used in conjunction with -lto-newpm-passes">;
 def lto_debug_pass_manager: F<"lto-debug-pass-manager">,
   HelpText<"Debug new pass manager">;
 def lto_new_pass_manager: F<"lto-new-pass-manager">,
   HelpText<"Use new pass manager">;
def opt_remarks_with_hotness: Flag<["--"], "opt-remarks-with-hotness">,
   HelpText<"Include hotness information in the optimization remarks file">;
 defm plugin_opt: Eq<"plugin-opt", "specifies LTO options for compatibility with GNU linkers">;
 def save_temps: F<"save-temps">;
 def thinlto_cache_dir: J<"thinlto-cache-dir=">,
   HelpText<"Path to ThinLTO cached object file directory">;
 defm thinlto_cache_policy: Eq<"thinlto-cache-policy", "Pruning policy for the ThinLTO cache">;
 def thinlto_jobs: J<"thinlto-jobs=">, HelpText<"Number of ThinLTO jobs">;
 
-def plugin_opt_O: J<"plugin-opt=O">, Alias<lto_O>;
-def plugin_opt_debug_pass_manager: F<"plugin-opt=debug-pass-manager">, Alias<lto_debug_pass_manager>;
-def plugin_opt_disable_verify: F<"plugin-opt=disable-verify">, Alias<disable_verify>;
-def plugin_opt_jobs_eq: J<"plugin-opt=jobs=">, Alias<thinlto_jobs>;
-def plugin_opt_lto_partitions_eq: J<"plugin-opt=lto-partitions=">, Alias<lto_partitions>;
+def: J<"plugin-opt=O">, Alias<lto_O>, HelpText<"Alias for -lto-O">;
+def: F<"plugin-opt=debug-pass-manager">,
+  Alias<lto_debug_pass_manager>, HelpText<"Alias for -lto-debug-pass-manager">;
+def: F<"plugin-opt=disable-verify">, Alias<disable_verify>, HelpText<"Alias for -disable-verify">;
+def: J<"plugin-opt=jobs=">, Alias<thinlto_jobs>, HelpText<"Alias for -thinlto-jobs">;
+def: J<"plugin-opt=lto-partitions=">, Alias<lto_partitions>, HelpText<"Alias for -lto-partitions">;
 def plugin_opt_mcpu_eq: J<"plugin-opt=mcpu=">;
-def plugin_opt_new_pass_manager: F<"plugin-opt=new-pass-manager">, Alias<lto_new_pass_manager>;
+def: F<"plugin-opt=new-pass-manager">,
+  Alias<lto_new_pass_manager>, HelpText<"Alias for -lto-new-pass-manager">;
 def plugin_opt_obj_path_eq: J<"plugin-opt=obj-path=">;
-def plugin_opt_sample_profile_eq: J<"plugin-opt=sample-profile=">, Alias<lto_sample_profile>;
-def plugin_opt_save_temps: F<"plugin-opt=save-temps">, Alias<save_temps>;
+def: J<"plugin-opt=sample-profile=">,
+  Alias<lto_sample_profile>, HelpText<"Alias for -lto-sample-profile">;
+def: F<"plugin-opt=save-temps">, Alias<save_temps>, HelpText<"Alias for -save-temps">;
 def plugin_opt_thinlto_emit_imports_files: F<"plugin-opt=thinlto-emit-imports-files">;
 def plugin_opt_thinlto_index_only: F<"plugin-opt=thinlto-index-only">;
 def plugin_opt_thinlto_index_only_eq: J<"plugin-opt=thinlto-index-only=">;
 def plugin_opt_thinlto_object_suffix_replace_eq: J<"plugin-opt=thinlto-object-suffix-replace=">;
 def plugin_opt_thinlto_prefix_replace_eq: J<"plugin-opt=thinlto-prefix-replace=">;
 
 // Ignore LTO plugin-related options.
 // clang -flto passes -plugin and -plugin-opt to the linker. This is required

lld/test/ELF/help.s

 # RUN: ld.lld --help 2>&1 | FileCheck %s
 # CHECK:  OPTIONS:
-# CHECK:  --output=<value>        Path to file to write output
-# CHECK:  --output <value>        Path to file to write output
+# CHECK:  --output=<value>        Alias for -o
+# CHECK:  --output <value>        Alias for -o
 # CHECK:  -o <path>               Path to file to write output