Don't rebuild LLVM for bolt optimization

Author: nikic

src/bootstrap/bolt.rs

@@ -172,8 +172,6 @@ pub struct Config {
     pub llvm_profile_use: Option<String>,
     pub llvm_profile_generate: bool,
     pub llvm_libunwind_default: Option<LlvmLibunwind>,
-    pub llvm_bolt_profile_generate: bool,
-    pub llvm_bolt_profile_use: Option<String>,
 
     pub build: TargetSelection,
     pub hosts: Vec<TargetSelection>,
@@ -869,15 +867,6 @@ impl Config {
         }
         config.llvm_profile_use = flags.llvm_profile_use;
         config.llvm_profile_generate = flags.llvm_profile_generate;
-        config.llvm_bolt_profile_generate = flags.llvm_bolt_profile_generate;
-        config.llvm_bolt_profile_use = flags.llvm_bolt_profile_use;
-
-        if config.llvm_bolt_profile_generate && config.llvm_bolt_profile_use.is_some() {
-            eprintln!(
-                "Cannot use both `llvm_bolt_profile_generate` and `llvm_bolt_profile_use` at the same time"
-            );
-            crate::detail_exit(1);
-        }
 
         // Infer the rest of the configuration.
 

src/bootstrap/config.rs

@@ -2220,10 +2220,6 @@ impl Step for ReproducibleArtifacts {
             tarball.add_file(path, ".", 0o644);
             added_anything = true;
         }
-        if let Some(path) = builder.config.llvm_bolt_profile_use.as_ref() {
-            tarball.add_file(path, ".", 0o644);
-            added_anything = true;
-        }
         if added_anything { Some(tarball.generate()) } else { None }
     }
 }

src/bootstrap/dist.rs

@@ -78,8 +78,6 @@ pub struct Flags {
     //
     // llvm_out/build/profiles/ is the location this writes to.
     pub llvm_profile_generate: bool,
-    pub llvm_bolt_profile_generate: bool,
-    pub llvm_bolt_profile_use: Option<String>,
 }
 
 #[derive(Debug)]
@@ -259,8 +257,6 @@ To learn more about a subcommand, run `./x.py <subcommand> -h`",
         opts.optmulti("D", "", "deny certain clippy lints", "OPT");
         opts.optmulti("W", "", "warn about certain clippy lints", "OPT");
         opts.optmulti("F", "", "forbid certain clippy lints", "OPT");
-        opts.optflag("", "llvm-bolt-profile-generate", "generate BOLT profile for LLVM build");
-        opts.optopt("", "llvm-bolt-profile-use", "use BOLT profile for LLVM build", "PROFILE");
 
         // We can't use getopt to parse the options until we have completed specifying which
         // options are valid, but under the current implementation, some options are conditional on
@@ -704,8 +700,6 @@ Arguments:
             rust_profile_generate: matches.opt_str("rust-profile-generate"),
             llvm_profile_use: matches.opt_str("llvm-profile-use"),
             llvm_profile_generate: matches.opt_present("llvm-profile-generate"),
-            llvm_bolt_profile_generate: matches.opt_present("llvm-bolt-profile-generate"),
-            llvm_bolt_profile_use: matches.opt_str("llvm-bolt-profile-use"),
         }
     }
 }

src/bootstrap/flags.rs

@@ -125,7 +125,6 @@ use crate::util::{
     exe, libdir, mtime, output, run, run_suppressed, symlink_dir, try_run_suppressed,
 };
 
-mod bolt;
 mod builder;
 mod cache;
 mod cc_detect;

src/bootstrap/lib.rs

@@ -16,7 +16,6 @@ use std::io;
 use std::path::{Path, PathBuf};
 use std::process::Command;
 
-use crate::bolt::{instrument_with_bolt_inplace, optimize_library_with_bolt_inplace};
 use crate::builder::{Builder, RunConfig, ShouldRun, Step};
 use crate::channel;
 use crate::config::{Config, TargetSelection};
@@ -345,12 +344,6 @@ impl Step for Llvm {
         if let Some(path) = builder.config.llvm_profile_use.as_ref() {
             cfg.define("LLVM_PROFDATA_FILE", &path);
         }
-        if builder.config.llvm_bolt_profile_generate
-            || builder.config.llvm_bolt_profile_use.is_some()
-        {
-            // Relocations are required for BOLT to work.
-            ldflags.push_all("-Wl,-q");
-        }
 
         // Disable zstd to avoid a dependency on libzstd.so.
         cfg.define("LLVM_ENABLE_ZSTD", "OFF");
@@ -520,34 +513,12 @@ impl Step for Llvm {
             }
         }
 
-        // After LLVM is built, we modify (instrument or optimize) the libLLVM.so library file
-        // in place. This is fine, because currently we do not support incrementally rebuilding
-        // LLVM after a configuration change, so to rebuild it the build files have to be removed,
-        // which will also remove these modified files.
-        if builder.config.llvm_bolt_profile_generate {
-            instrument_with_bolt_inplace(&get_built_llvm_lib_path(&res.llvm_config));
-        }
-        if let Some(path) = &builder.config.llvm_bolt_profile_use {
-            optimize_library_with_bolt_inplace(
-                &get_built_llvm_lib_path(&res.llvm_config),
-                &Path::new(path),
-            );
-        }
-
         t!(stamp.write());
 
         res
     }
 }
 
-/// Returns path to a built LLVM library (libLLVM.so).
-/// Assumes that we have built LLVM into a single library file.
-fn get_built_llvm_lib_path(llvm_config_path: &Path) -> PathBuf {
-    let mut cmd = Command::new(llvm_config_path);
-    cmd.arg("--libfiles");
-    PathBuf::from(output(&mut cmd).trim())
-}
-
 fn check_llvm_version(builder: &Builder<'_>, llvm_config: &Path) {
     if !builder.config.llvm_version_check {
         return;