Remove the "codegen" profile from bootstrap

This profile originally made sense when download-ci-llvm = if-unchanged
didn't exist and we had the bad tradeoff of "never modify or always
compile".

Thankfully, these grim times are over and we have discovered clean
water, so the only differentiator between the two profiles is the
codegen profile having LLVM assertions. Adding them doesn't cause that
much of a slowdown, <10% on UI tests from an unscientific benchmark.

It also had LLVM warnings when compiling, which makes sense for every
compiler contributor brave enough to compile LLVM.

The way I removed is by just issueing a nice error message. Given that
everyone with this profile should be a contributor and not someone like
a distro who is more upset when things break, this should be fine.
If it isn't, we can always fall back to just letting codegen mean
compiler.

src/bootstrap/defaults/config.compiler.toml

@@ -19,5 +19,10 @@ lto = "off"
 frame-pointers = true
 
 [llvm]
+# This enables debug-assertions in LLVM,
+# catching logic errors in codegen much earlier in the process.
+assertions = true
+# Enable warnings during the LLVM compilation (when LLVM is changed, causing a compilation)
+enable-warnings = true
 # Will download LLVM from CI if available on your platform.
 download-ci-llvm = "if-unchanged"

src/bootstrap/src/core/build_steps/setup.rs

@@ -19,7 +19,6 @@ mod tests;
 #[derive(Clone, Copy, Debug, Eq, PartialEq, Hash)]
 pub enum Profile {
     Compiler,
-    Codegen,
     Library,
     Tools,
     Dist,
@@ -48,15 +47,14 @@ impl Profile {
     pub fn all() -> impl Iterator<Item = Self> {
         use Profile::*;
         // N.B. these are ordered by how they are displayed, not alphabetically
-        [Library, Compiler, Codegen, Tools, Dist, None].iter().copied()
+        [Library, Compiler, Tools, Dist, None].iter().copied()
     }
 
     pub fn purpose(&self) -> String {
         use Profile::*;
         match self {
             Library => "Contribute to the standard library",
             Compiler => "Contribute to the compiler itself",
-            Codegen => "Contribute to the compiler, and also modify LLVM or codegen",
             Tools => "Contribute to tools which depend on the compiler, but do not modify it directly (e.g. rustdoc, clippy, miri)",
             Dist => "Install Rust from source",
             None => "Do not modify `config.toml`"
@@ -75,7 +73,6 @@ impl Profile {
     pub fn as_str(&self) -> &'static str {
         match self {
             Profile::Compiler => "compiler",
-            Profile::Codegen => "codegen",
             Profile::Library => "library",
             Profile::Tools => "tools",
             Profile::Dist => "dist",
@@ -91,12 +88,15 @@ impl FromStr for Profile {
         match s {
             "lib" | "library" => Ok(Profile::Library),
             "compiler" => Ok(Profile::Compiler),
-            "llvm" | "codegen" => Ok(Profile::Codegen),
             "maintainer" | "dist" | "user" => Ok(Profile::Dist),
             "tools" | "tool" | "rustdoc" | "clippy" | "miri" | "rustfmt" | "rls" => {
                 Ok(Profile::Tools)
             }
             "none" => Ok(Profile::None),
+            "llvm" | "codegen" => Err(format!(
+                "the \"llvm\" and \"codegen\" profiles have been removed,\
+                use \"compiler\" instead which has the same functionality"
+            )),
             _ => Err(format!("unknown profile: '{s}'")),
         }
     }
@@ -170,22 +170,13 @@ impl Step for Profile {
     }
 
     fn run(self, builder: &Builder<'_>) {
-        // During ./x.py setup once you select the codegen profile.
-        // The submodule will be downloaded. It does not work in the
-        // tarball case since they don't include Git and submodules
-        // are already included.
-        if !builder.rust_info().is_from_tarball() {
-            if self == Profile::Codegen {
-                builder.update_submodule(&Path::new("src/llvm-project"));
-            }
-        }
-        setup(&builder.build.config, self)
+        setup(&builder.build.config, self);
     }
 }
 
 pub fn setup(config: &Config, profile: Profile) {
     let suggestions: &[&str] = match profile {
-        Profile::Codegen | Profile::Compiler | Profile::None => &["check", "build", "test"],
+        Profile::Compiler | Profile::None => &["check", "build", "test"],
         Profile::Tools => &[
             "check",
             "build",

src/bootstrap/src/utils/change_tracker.rs

@@ -124,4 +124,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "A new `rust.frame-pointers` option has been introduced and made the default in the compiler and codegen profiles.",
     },
+    ChangeInfo {
+        change_id: 121278,
+        severity: ChangeSeverity::Warning,
+        summary: "The \"codegen\"/\"llvm\" profile has been removed and replaced with \"compiler\", use it instead for the same behavior.",
+    },
 ];

triagebot.toml

@@ -627,11 +627,6 @@ This PR modifies `config.example.toml`.
 If appropriate, please update `CONFIG_CHANGE_HISTORY` in `src/bootstrap/src/utils/change_tracker.rs`.
 """
 
-[mentions."src/bootstrap/defaults/config.compiler.toml"]
-message = "This PR changes src/bootstrap/defaults/config.compiler.toml. If appropriate, please also update `config.codegen.toml` so the defaults are in sync."
-[mentions."src/bootstrap/defaults/config.codegen.toml"]
-message = "This PR changes src/bootstrap/defaults/config.codegen.toml. If appropriate, please also update `config.compiler.toml` so the defaults are in sync."
-
 [mentions."src/bootstrap/src/core/build_steps/llvm.rs"]
 message = "This PR changes how LLVM is built. Consider updating src/bootstrap/download-ci-llvm-stamp."