Build with -Zannotate-moves by default (non-stage-0 only)

bootstrap.example.toml

@@ -828,6 +828,17 @@
 # If an explicit setting is given, it will be used for all parts of the codebase.
 #rust.new-symbol-mangling = true|false (see comment)
 
+# Enable move/copy annotations for profiler visibility. When enabled, compiler-generated
+# move and copy operations will be annotated with debug info that makes them visible in
+# profilers. This is helpful when profiling to see where expensive copies/moves occur.
+# Defaults to true (enabled).
+#rust.annotate-moves = true
+
+# Size limit in bytes for move/copy annotations. Only types at or above this size will
+# be annotated. If not specified, uses the default limit (65 bytes). Only takes effect
+# if annotate-moves is enabled.
+#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

@@ -654,6 +654,16 @@ impl Builder<'_> {
             rustflags.arg("-Csymbol-mangling-version=legacy");
         }
 
+        // Enable move/copy annotations for profiler visibility if configured
+        // Skip stage 0 since the bootstrap compiler doesn't support this flag yet
+        if self.config.rust_annotate_moves.unwrap_or(true) && 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

@@ -216,6 +216,8 @@ pub struct Config {
     pub rust_thin_lto_import_instr_limit: Option<u32>,
     pub rust_randomize_layout: bool,
     pub rust_remap_debuginfo: bool,
+    pub rust_annotate_moves: Option<bool>,
+    pub rust_annotate_moves_size_limit: Option<u64>,
     pub rust_new_symbol_mangling: Option<bool>,
     pub rust_profile_use: Option<String>,
     pub rust_profile_generate: Option<String>,
@@ -558,6 +560,8 @@ impl Config {
             llvm_libunwind: rust_llvm_libunwind,
             control_flow_guard: rust_control_flow_guard,
             ehcont_guard: rust_ehcont_guard,
+            annotate_moves: rust_annotate_moves,
+            annotate_moves_size_limit: rust_annotate_moves_size_limit,
             new_symbol_mangling: rust_new_symbol_mangling,
             profile_generate: rust_profile_generate,
             profile_use: rust_profile_use,
@@ -1398,6 +1402,8 @@ impl Config {
             reproducible_artifacts: flags_reproducible_artifact,
             reuse: build_reuse.map(PathBuf::from),
             rust_analyzer_info,
+            rust_annotate_moves,
+            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

@@ -59,6 +59,8 @@ define_config! {
         llvm_libunwind: Option<String> = "llvm-libunwind",
         control_flow_guard: Option<bool> = "control-flow-guard",
         ehcont_guard: Option<bool> = "ehcont-guard",
+        annotate_moves: Option<bool> = "annotate-moves",
+        annotate_moves_size_limit: Option<u64> = "annotate-moves-size-limit",
         new_symbol_mangling: Option<bool> = "new-symbol-mangling",
         profile_generate: Option<String> = "profile-generate",
         profile_use: Option<String> = "profile-use",
@@ -363,6 +365,8 @@ pub fn check_incompatible_options_for_ci_rustc(
         llvm_libunwind: _,
         control_flow_guard: _,
         ehcont_guard: _,
+        annotate_moves: _,
+        annotate_moves_size_limit: _,
         new_symbol_mangling: _,
         profile_generate: _,
         profile_use: _,