[LLD][ELF][NewPM] Add option to force legacy PM

[aeubanks]

Summary

In preparation for the NPM switch.

[MaskRay]

lld/ELF/Options.td

529

This should probably be --no-lto-new-pass-manager.

FF -> BB

[aeubanks]

use BB

lld/ELF/Options.td

529

Thanks, I wasn't aware of that.

[MaskRay]

LGTM.

lld/test/ELF/lto/new-pass-manager.ll

9

%t2.o -> /dev/null since the output is not used

lld/ELF/Driver.cpp

static void readConfigs(opt::InputArgList &args) {
   config->ignoreFunctionAddressEquality =
       args.hasArg(OPT_ignore_function_address_equality);
   config->init = args.getLastArgValue(OPT_init, "_init");
   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->ltoNewPassManager = args.hasFlag(OPT_lto_new_pass_manager,
+                                           OPT_lto_no_new_pass_manager, false);
   config->ltoNewPmPasses = args.getLastArgValue(OPT_lto_newpm_passes);
   config->ltoWholeProgramVisibility =
       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);

lld/ELF/Options.td

 
 // LTO-related options.
 def lto_aa_pipeline: JJ<"lto-aa-pipeline=">,
   HelpText<"AA pipeline to run during LTO. Used in conjunction with -lto-newpm-passes">;
 def lto_debug_pass_manager: FF<"lto-debug-pass-manager">,
   HelpText<"Debug new pass manager">;
 def lto_emit_asm: FF<"lto-emit-asm">,
   HelpText<"Emit assembly code">;
 def lto_new_pass_manager: FF<"lto-new-pass-manager">,
   HelpText<"Use new pass manager">;
+def lto_no_new_pass_manager: FF<"lto-no-new-pass-manager">,
+  HelpText<"Use legacy pass manager">;
 def lto_newpm_passes: JJ<"lto-newpm-passes=">,
   HelpText<"Passes to run during LTO">;
 def lto_O: JJ<"lto-O">, MetaVarName<"<opt-level>">,
   HelpText<"Optimization level for LTO">;
 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">;

lld/test/ELF/lto/new-pass-manager.ll

 ; REQUIRES: x86
 ; RUN: opt -module-summary %s -o %t.o
 
 ; Test new-pass-manager and debug-pass-manager option
 ; RUN: ld.lld --plugin-opt=new-pass-manager --plugin-opt=debug-pass-manager -o %t2.o %t.o 2>&1 | FileCheck %s
 ; RUN: ld.lld --plugin-opt=new-pass-manager --lto-debug-pass-manager -o %t2.o %t.o 2>&1 | FileCheck %s
 ; RUN: ld.lld --lto-new-pass-manager --plugin-opt=debug-pass-manager -o %t2.o %t.o 2>&1 | FileCheck %s
 ; RUN: ld.lld --lto-new-pass-manager --lto-debug-pass-manager -o %t2.o %t.o 2>&1 | FileCheck %s
+; RUN: ld.lld --lto-new-pass-manager --lto-no-new-pass-manager --lto-debug-pass-manager -o %t2.o %t.o 2>&1 | FileCheck %s --check-prefix=LEGACY
 
 ; CHECK: Starting llvm::Module pass manager run
 ; CHECK: Finished llvm::Module pass manager run
+; LEGACY-NOT: Starting llvm::Module pass manager run
 
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"