[llvm] [LTO] Remove Config.UseDefaultPipeline (PR #82587)

[Igor Kudrin via llvm-commits]

https://github.com/igorkudrin created https://github.com/llvm/llvm-project/pull/82587

This option is not used. It was added in [D122133](https://reviews.llvm.org/D122133), 5856f30b, with the only usage in `ClangLinkerWrapper.cpp`, which was later updated in a1d57fc2, and then finally removed in [D142650](https://reviews.llvm.org/D142650), 6185246f.

>From 93daff745d0a07dd4ec68aa8b696dfee70f9bbdb Mon Sep 17 00:00:00 2001
From: Igor Kudrin <ikudrin at accesssoftek.com>
Date: Wed, 21 Feb 2024 19:50:56 -0800
Subject: [PATCH] [LTO] Remove Config.UseDefaultPipeline

This option is not used. It was added in https://reviews.llvm.org/D122133,
with the only usage in `ClangLinkerWrapper.cpp`, which was later removed
in https://reviews.llvm.org/D142650.
---
 llvm/include/llvm/LTO/Config.h | 3 ---
 llvm/lib/LTO/LTOBackend.cpp    | 2 --
 2 files changed, 5 deletions(-)

diff --git a/llvm/include/llvm/LTO/Config.h b/llvm/include/llvm/LTO/Config.h
index 6fb55f1cf1686a..482b6e55a19d35 100644
--- a/llvm/include/llvm/LTO/Config.h
+++ b/llvm/include/llvm/LTO/Config.h
@@ -60,9 +60,6 @@ struct Config {
   bool VerifyEach = false;
   bool DisableVerify = false;
 
-  /// Use the standard optimization pipeline.
-  bool UseDefaultPipeline = false;
-
   /// Flag to indicate that the optimizer should not assume builtins are present
   /// on the target.
   bool Freestanding = false;
diff --git a/llvm/lib/LTO/LTOBackend.cpp b/llvm/lib/LTO/LTOBackend.cpp
index 7b3a7590dfa743..6cfe67779b1a7d 100644
--- a/llvm/lib/LTO/LTOBackend.cpp
+++ b/llvm/lib/LTO/LTOBackend.cpp
@@ -330,8 +330,6 @@ static void runNewPMPasses(const Config &Conf, Module &Mod, TargetMachine *TM,
       report_fatal_error(Twine("unable to parse pass pipeline description '") +
                          Conf.OptPipeline + "': " + toString(std::move(Err)));
     }
-  } else if (Conf.UseDefaultPipeline) {
-    MPM.addPass(PB.buildPerModuleDefaultPipeline(OL));
   } else if (IsThinLTO) {
     MPM.addPass(PB.buildThinLTODefaultPipeline(OL, ImportSummary));
   } else {