[lld] Add --no-lto-whole-program-visibility

[tejohnson]

Summary

Enables overriding earlier --lto-whole-program-visibility.

Variant of D91583 while discussing alternate ways to identify and
handle the --export-dynamic case.

[MaskRay]

This looks good.

lld/test/ELF/lto/devirt_vcall_vis_public.ll

37

Could you also add some comments that the existing --export-dynamic is to retain the symbols?

42

A --lto-whole-program-visibility --no-lto-whole-program-visibility RUN list is sufficient, no need for the previous RUN line.

[tejohnson]

lld/test/ELF/lto/devirt_vcall_vis_public.ll

37

Will do.

42

I assume you mean the variant I added with just the explicit --no-lto-whole-program-visibility, and not --lto-whole-program-visibility. Yeah that seems redundant, will remove.

[tejohnson]

Address comments

[MaskRay]

Looks great!

lld/ELF/Driver.cpp

static void readConfigs(opt::InputArgList &args) {
   config->ltoAAPipeline = args.getLastArgValue(OPT_lto_aa_pipeline);
   config->ltoCSProfileGenerate = args.hasArg(OPT_lto_cs_profile_generate);
   config->ltoCSProfileFile = args.getLastArgValue(OPT_lto_cs_profile_file);
   config->ltoDebugPassManager = args.hasArg(OPT_lto_debug_pass_manager);
   config->ltoEmitAsm = args.hasArg(OPT_lto_emit_asm);
   config->ltoNewPassManager = args.hasArg(OPT_lto_new_pass_manager);
   config->ltoNewPmPasses = args.getLastArgValue(OPT_lto_newpm_passes);
   config->ltoWholeProgramVisibility =
-      args.hasArg(OPT_lto_whole_program_visibility);
+      args.hasFlag(OPT_lto_whole_program_visibility,
+                   OPT_no_lto_whole_program_visibility, false);
   config->ltoo = args::getInteger(args, OPT_lto_O, 2);
   config->ltoObjPath = args.getLastArgValue(OPT_lto_obj_path_eq);
   config->ltoPartitions = args::getInteger(args, OPT_lto_partitions, 1);
   config->ltoSampleProfile = args.getLastArgValue(OPT_lto_sample_profile);
   config->ltoBasicBlockSections =
       args.getLastArgValue(OPT_lto_basic_block_sections);
   config->ltoUniqueBasicBlockSectionNames =
       args.hasFlag(OPT_lto_unique_basic_block_section_names,

lld/ELF/Options.td

def lto_partitions: JJ<"lto-partitions=">,
   HelpText<"Number of LTO codegen partitions">;
 def lto_cs_profile_generate: FF<"lto-cs-profile-generate">,
   HelpText<"Perform context sensitive PGO instrumentation">;
 def lto_cs_profile_file: JJ<"lto-cs-profile-file=">,
   HelpText<"Context sensitive profile file path">;
 def lto_obj_path_eq: JJ<"lto-obj-path=">;
 def lto_sample_profile: JJ<"lto-sample-profile=">,
   HelpText<"Sample profile file path">;
-def lto_whole_program_visibility: FF<"lto-whole-program-visibility">,
-  HelpText<"Asserts that the LTO link has whole program visibility">;
+defm lto_whole_program_visibility: BB<"lto-whole-program-visibility",
+  "Asserts that the LTO link has whole program visibility",
+  "Asserts that the LTO link does not have whole program visibility">;
 def disable_verify: F<"disable-verify">;
 defm mllvm: Eq<"mllvm", "Additional arguments to forward to LLVM's option processing">;
 def opt_remarks_filename: Separate<["--"], "opt-remarks-filename">,
   HelpText<"YAML output file for optimization remarks">;
 def opt_remarks_passes: Separate<["--"], "opt-remarks-passes">,
   HelpText<"Regex for the passes that need to be serialized to the output file">;
 def opt_remarks_with_hotness: FF<"opt-remarks-with-hotness">,
   HelpText<"Include hotness information in the optimization remarks file">;

lld/test/ELF/lto/devirt_vcall_vis_public.ll

 ; REQUIRES: x86
 ; Test that --lto-whole-program-visibility enables devirtualization.
 
+; Note that the --export-dynamic used below is simply to ensure symbols are
+; retained during linking.
+
 ; Index based WPD
 ; Generate unsplit module with summary for ThinLTO index-based WPD.
 ; RUN: opt --thinlto-bc -o %t2.o %s
 ; RUN: ld.lld %t2.o -o %t3 -save-temps --lto-whole-program-visibility \
 ; RUN:   -mllvm -pass-remarks=. --export-dynamic 2>&1 | FileCheck %s --check-prefix=REMARK
 ; RUN: llvm-dis %t2.o.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-IR
 
 ; Hybrid WPD

 
 ; Try everything again but without -whole-program-visibility to confirm
 ; WPD fails
 
 ; Index based WPD
 ; RUN: ld.lld %t2.o -o %t3 -save-temps \
 ; RUN:   -mllvm -pass-remarks=. --export-dynamic 2>&1 | FileCheck %s --implicit-check-not single-impl --allow-empty
 ; RUN: llvm-dis %t2.o.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-NODEVIRT-IR
+; Ensure --no-lto-whole-program-visibility overrides explicit --lto-whole-program-visibility.
+; RUN: ld.lld %t2.o -o %t3 -save-temps --lto-whole-program-visibility --no-lto-whole-program-visibility \
+; RUN:   -mllvm -pass-remarks=. --export-dynamic 2>&1 | FileCheck %s --implicit-check-not single-impl --allow-empty
+; RUN: llvm-dis %t2.o.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-NODEVIRT-IR
 
 ; Hybrid WPD
 ; RUN: ld.lld %t.o -o %t3 -save-temps \
 ; RUN:   -mllvm -pass-remarks=. --export-dynamic 2>&1 | FileCheck %s --implicit-check-not single-impl --allow-empty
 ; RUN: llvm-dis %t.o.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-NODEVIRT-IR
 
 ; Regular LTO WPD
 ; RUN: ld.lld %t4.o -o %t3 -save-temps \
 ; RUN:   -mllvm -pass-remarks=. --export-dynamic 2>&1 | FileCheck %s --implicit-check-not single-impl --allow-empty
 ; RUN: llvm-dis %t3.0.4.opt.bc -o - | FileCheck %s --check-prefix=CHECK-NODEVIRT-IR