Build with -Zannotate-moves by default

Build rustc and tools with -Zannotate-moves by default. Adds toml config
options to set the annotation size limit.

This has no measurable effect on output binary size or compile time.

Author: Jeremy Fitzhardinge

bootstrap.example.toml

@@ -831,6 +831,11 @@
 # If an explicit setting is given, it will be used for all parts of the codebase.
 #rust.new-symbol-mangling = true|false (see comment)
 
+# Size limit in bytes for move/copy annotations (-Zannotate-moves). Only types
+# at or above this size will be annotated. If not specified, uses the default
+# limit (65 bytes).
+#rust.annotate-moves-size-limit = 65
+
 # Select LTO mode that will be used for compiling rustc. By default, thin local LTO
 # (LTO within a single crate) is used (like for any Rust crate). You can also select
 # "thin" or "fat" to apply Thin/Fat LTO to the `rustc_driver` dylib, or "off" to disable

src/bootstrap/src/core/builder/cargo.rs

@@ -673,6 +673,16 @@ impl Builder<'_> {
             rustflags.arg("-Csymbol-mangling-version=legacy");
         }
 
+        // Always enable move/copy annotations for profiler visibility (non-stage0 only).
+        // Note that -Zannotate-moves is only effective with debugging info enabled.
+        if build_compiler_stage >= 1 {
+            if let Some(limit) = self.config.rust_annotate_moves_size_limit {
+                rustflags.arg(&format!("-Zannotate-moves={limit}"));
+            } else {
+                rustflags.arg("-Zannotate-moves");
+            }
+        }
+
         // FIXME: the following components don't build with `-Zrandomize-layout` yet:
         // - rust-analyzer, due to the rowan crate
         // so we exclude an entire category of steps here due to lack of fine-grained control over

src/bootstrap/src/core/config/config.rs

@@ -217,6 +217,7 @@ pub struct Config {
     pub rust_randomize_layout: bool,
     pub rust_remap_debuginfo: bool,
     pub rust_new_symbol_mangling: Option<bool>,
+    pub rust_annotate_moves_size_limit: Option<u64>,
     pub rust_profile_use: Option<String>,
     pub rust_profile_generate: Option<String>,
     pub rust_lto: RustcLto,
@@ -561,6 +562,7 @@ impl Config {
             control_flow_guard: rust_control_flow_guard,
             ehcont_guard: rust_ehcont_guard,
             new_symbol_mangling: rust_new_symbol_mangling,
+            annotate_moves_size_limit: rust_annotate_moves_size_limit,
             profile_generate: rust_profile_generate,
             profile_use: rust_profile_use,
             download_rustc: rust_download_rustc,
@@ -1405,6 +1407,7 @@ impl Config {
             reproducible_artifacts: flags_reproducible_artifact,
             reuse: build_reuse.map(PathBuf::from),
             rust_analyzer_info,
+            rust_annotate_moves_size_limit,
             rust_break_on_ice: rust_break_on_ice.unwrap_or(true),
             rust_codegen_backends: rust_codegen_backends
                 .map(|backends| parse_codegen_backends(backends, "rust"))

src/bootstrap/src/core/config/toml/rust.rs

@@ -60,6 +60,7 @@ define_config! {
         control_flow_guard: Option<bool> = "control-flow-guard",
         ehcont_guard: Option<bool> = "ehcont-guard",
         new_symbol_mangling: Option<bool> = "new-symbol-mangling",
+        annotate_moves_size_limit: Option<u64> = "annotate-moves-size-limit",
         profile_generate: Option<String> = "profile-generate",
         profile_use: Option<String> = "profile-use",
         // ignored; this is set from an env var set by bootstrap.py
@@ -364,6 +365,7 @@ pub fn check_incompatible_options_for_ci_rustc(
         control_flow_guard: _,
         ehcont_guard: _,
         new_symbol_mangling: _,
+        annotate_moves_size_limit: _,
         profile_generate: _,
         profile_use: _,
         download_rustc: _,

src/bootstrap/src/utils/change_tracker.rs

@@ -591,4 +591,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "`yarn` is now used instead of `npm` to install dependencies for some extra tidy checks. Use `build.yarn` to manually specify the path to `yarn` (`build.npm` is no longer used).",
     },
+    ChangeInfo {
+        change_id: 148803,
+        severity: ChangeSeverity::Info,
+        summary: "The `-Zannotate-moves` option is now always enabled when building rustc, sysroot and tools.",
+    },
 ];