From ff227c4a2d8a2fad5abf322f6f1391ae6779197f Mon Sep 17 00:00:00 2001
From: Alex Crichton <alex@alexcrichton.com>
Date: Fri, 9 Mar 2018 13:19:00 -0800
Subject: [PATCH] rustbuild: Remove ThinLTO-related configuration

This commit removes some ThinLTO/codegen unit cruft primarily only needed during
the initial phase where we were adding ThinLTO support to rustc itself. The
current bootstrap compiler knows about ThinLTO and has it enabled by default for
multi-CGU builds which are also enabled by default. One CGU builds (aka
disabling ThinLTO) can be achieved by configuring the number of codegen units to
1 for a particular builds.

This also changes the defaults for our dist builders to go back to multiple
CGUs. Unfortunately we're seriously bleeding for cycle time on the bots right
now so we need to recover any time we can.
---
 src/bootstrap/bin/rustc.rs |  3 ---
 src/bootstrap/builder.rs   | 11 -----------
 src/bootstrap/config.rs    |  5 -----
 src/bootstrap/configure.py |  1 -
 src/ci/run.sh              |  1 -
 5 files changed, 21 deletions(-)

diff --git a/src/bootstrap/bin/rustc.rs b/src/bootstrap/bin/rustc.rs
index 6c3c48aba72..8ccee45f3c5 100644
--- a/src/bootstrap/bin/rustc.rs
+++ b/src/bootstrap/bin/rustc.rs
@@ -175,9 +175,6 @@ fn main() {
         if let Ok(s) = env::var("RUSTC_CODEGEN_UNITS") {
             cmd.arg("-C").arg(format!("codegen-units={}", s));
         }
-        if env::var("RUSTC_THINLTO").is_ok() {
-            cmd.arg("-Ccodegen-units=16").arg("-Zthinlto");
-        }
 
         // Emit save-analysis info.
         if env::var("RUSTC_SAVE_ANALYSIS") == Ok("api".to_string()) {
diff --git a/src/bootstrap/builder.rs b/src/bootstrap/builder.rs
index 22656e5a9da..13be709fddc 100644
--- a/src/bootstrap/builder.rs
+++ b/src/bootstrap/builder.rs
@@ -792,17 +792,6 @@ impl<'a> Builder<'a> {
             if cmd != "bench" {
                 cargo.arg("--release");
             }
-
-            if self.config.rust_codegen_units.is_none() &&
-               self.build.is_rust_llvm(compiler.host) &&
-               self.config.rust_thinlto {
-                cargo.env("RUSTC_THINLTO", "1");
-            } else if self.config.rust_codegen_units.is_none() {
-                // Generally, if ThinLTO has been disabled for some reason, we
-                // want to set the codegen units to 1. However, we shouldn't do
-                // this if the option was specifically set by the user.
-                cargo.env("RUSTC_CODEGEN_UNITS", "1");
-            }
         }
 
         if self.config.locked_deps {
diff --git a/src/bootstrap/config.rs b/src/bootstrap/config.rs
index f15d4d35858..4bb0ae8b0b6 100644
--- a/src/bootstrap/config.rs
+++ b/src/bootstrap/config.rs
@@ -86,7 +86,6 @@ pub struct Config {
     // rust codegen options
     pub rust_optimize: bool,
     pub rust_codegen_units: Option<u32>,
-    pub rust_thinlto: bool,
     pub rust_debug_assertions: bool,
     pub rust_debuginfo: bool,
     pub rust_debuginfo_lines: bool,
@@ -269,7 +268,6 @@ impl Default for StringOrBool {
 struct Rust {
     optimize: Option<bool>,
     codegen_units: Option<u32>,
-    thinlto: Option<bool>,
     debug_assertions: Option<bool>,
     debuginfo: Option<bool>,
     debuginfo_lines: Option<bool>,
@@ -427,7 +425,6 @@ impl Config {
 
         // Store off these values as options because if they're not provided
         // we'll infer default values for them later
-        let mut thinlto = None;
         let mut llvm_assertions = None;
         let mut debuginfo_lines = None;
         let mut debuginfo_only_std = None;
@@ -471,7 +468,6 @@ impl Config {
             optimize = rust.optimize;
             ignore_git = rust.ignore_git;
             debug_jemalloc = rust.debug_jemalloc;
-            thinlto = rust.thinlto;
             set(&mut config.rust_optimize_tests, rust.optimize_tests);
             set(&mut config.rust_debuginfo_tests, rust.debuginfo_tests);
             set(&mut config.codegen_tests, rust.codegen_tests);
@@ -559,7 +555,6 @@ impl Config {
             "stable" | "beta" | "nightly" => true,
             _ => false,
         };
-        config.rust_thinlto = thinlto.unwrap_or(true);
         config.rust_debuginfo_lines = debuginfo_lines.unwrap_or(default);
         config.rust_debuginfo_only_std = debuginfo_only_std.unwrap_or(default);
 
diff --git a/src/bootstrap/configure.py b/src/bootstrap/configure.py
index e9b4a233d0a..97da7cae07f 100755
--- a/src/bootstrap/configure.py
+++ b/src/bootstrap/configure.py
@@ -71,7 +71,6 @@ o("full-tools", None, "enable all tools")
 # Optimization and debugging options. These may be overridden by the release
 # channel, etc.
 o("optimize", "rust.optimize", "build optimized rust code")
-o("thinlto", "rust.thinlto", "build Rust with ThinLTO enabled")
 o("optimize-llvm", "llvm.optimize", "build optimized LLVM")
 o("llvm-assertions", "llvm.assertions", "build LLVM with assertions")
 o("debug-assertions", "rust.debug-assertions", "build with debugging assertions")
diff --git a/src/ci/run.sh b/src/ci/run.sh
index 79300e08a7d..29126e7cc9b 100755
--- a/src/ci/run.sh
+++ b/src/ci/run.sh
@@ -46,7 +46,6 @@ export RUST_RELEASE_CHANNEL=nightly
 if [ "$DEPLOY$DEPLOY_ALT" != "" ]; then
   RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --release-channel=$RUST_RELEASE_CHANNEL"
   RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --enable-llvm-static-stdcpp"
-  RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-thinlto"
 
   if [ "$NO_LLVM_ASSERTIONS" = "1" ]; then
     RUST_CONFIGURE_ARGS="$RUST_CONFIGURE_ARGS --disable-llvm-assertions"