Add a bootstrap option for LLVM with zstd. Defaults to true on Linux and false elsewhere.

Author: khuey

config.example.toml

@@ -713,6 +713,11 @@
 # option will override this if set.
 #llvm-libunwind = 'no'
 
+# Global default for llvm-libzstd for all targets. See the target-specific
+# documentation for llvm-libzstd below. Note that the target-specific
+# option will override this if set.
+#llvm-libzstd = false
+
 # Enable Windows Control Flow Guard checks in the standard library.
 # This only applies from stage 1 onwards, and only for Windows targets.
 #control-flow-guard = false
@@ -816,6 +821,9 @@
 # it must link to `libgcc_eh.a` to get a working output, and this option have no effect.
 #llvm-libunwind = 'no' if Linux, 'in-tree' if Fuchsia
 
+# Enable LLVM to use zstd for compression.
+#llvm-libzstd = if linux { true } else { false }
+
 # Build the sanitizer runtimes for this target.
 # This option will override the same option under [build] section.
 #sanitizers = build.sanitizers (bool)

src/bootstrap/src/core/build_steps/llvm.rs

@@ -819,11 +819,13 @@ fn configure_llvm(builder: &Builder<'_>, target: TargetSelection, cfg: &mut cmak
     // Libraries for ELF section compression.
     if !target.is_windows() {
         cfg.define("LLVM_ENABLE_ZLIB", "ON");
-        cfg.define("LLVM_ENABLE_ZSTD", "ON");
-        cfg.define("LLVM_USE_STATIC_ZSTD", "TRUE");
     } else {
         cfg.define("LLVM_ENABLE_ZLIB", "OFF");
-        cfg.define("LLVM_ENABLE_ZSTD", "OFF");
+    }
+
+    if builder.config.llvm_libzstd(target) {
+        cfg.define("LLVM_ENABLE_ZSTD", "FORCE_ON");
+        cfg.define("LLVM_USE_STATIC_ZSTD", "TRUE");
     }
 
     if let Some(ref linker) = builder.config.llvm_use_linker {

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

@@ -282,6 +282,7 @@ pub struct Config {
     pub llvm_profile_use: Option<String>,
     pub llvm_profile_generate: bool,
     pub llvm_libunwind_default: Option<LlvmLibunwind>,
+    pub llvm_libzstd_default: Option<bool>,
     pub enable_bolt_settings: bool,
 
     pub reproducible_artifacts: Vec<String>,
@@ -547,6 +548,7 @@ pub struct Target {
     /// Some(path to FileCheck) if one was specified.
     pub llvm_filecheck: Option<PathBuf>,
     pub llvm_libunwind: Option<LlvmLibunwind>,
+    pub llvm_libzstd: Option<bool>,
     pub cc: Option<PathBuf>,
     pub cxx: Option<PathBuf>,
     pub ar: Option<PathBuf>,
@@ -1103,6 +1105,7 @@ define_config! {
         jemalloc: Option<bool> = "jemalloc",
         test_compare_mode: Option<bool> = "test-compare-mode",
         llvm_libunwind: Option<String> = "llvm-libunwind",
+        llvm_libzstd: Option<bool> = "llvm-libzstd",
         control_flow_guard: Option<bool> = "control-flow-guard",
         ehcont_guard: Option<bool> = "ehcont-guard",
         new_symbol_mangling: Option<bool> = "new-symbol-mangling",
@@ -1129,6 +1132,7 @@ define_config! {
         llvm_has_rust_patches: Option<bool> = "llvm-has-rust-patches",
         llvm_filecheck: Option<String> = "llvm-filecheck",
         llvm_libunwind: Option<String> = "llvm-libunwind",
+        llvm_libzstd: Option<bool> = "llvm-libzstd",
         sanitizers: Option<bool> = "sanitizers",
         profiler: Option<StringOrBool> = "profiler",
         rpath: Option<bool> = "rpath",
@@ -1630,6 +1634,7 @@ impl Config {
                 jemalloc,
                 test_compare_mode,
                 llvm_libunwind,
+                llvm_libzstd,
                 control_flow_guard,
                 ehcont_guard,
                 new_symbol_mangling,
@@ -1716,6 +1721,7 @@ impl Config {
             set(&mut config.ehcont_guard, ehcont_guard);
             config.llvm_libunwind_default =
                 llvm_libunwind.map(|v| v.parse().expect("failed to parse rust.llvm-libunwind"));
+            config.llvm_libzstd_default = llvm_libzstd;
 
             if let Some(ref backends) = codegen_backends {
                 let available_backends = ["llvm", "cranelift", "gcc"];
@@ -1908,6 +1914,7 @@ impl Config {
                         panic!("failed to parse target.{triple}.llvm-libunwind")
                     })
                 });
+                target.llvm_libzstd = cfg.llvm_libzstd;
                 if let Some(s) = cfg.no_std {
                     target.no_std = s;
                 }
@@ -2394,6 +2401,14 @@ impl Config {
             })
     }
 
+    pub fn llvm_libzstd(&self, target: TargetSelection) -> bool {
+        self.target_config
+            .get(&target)
+            .and_then(|t| t.llvm_libzstd)
+            .or(self.llvm_libzstd_default)
+            .unwrap_or(target.contains("linux"))
+    }
+
     pub fn split_debuginfo(&self, target: TargetSelection) -> SplitDebuginfo {
         self.target_config
             .get(&target)
@@ -2698,6 +2713,7 @@ fn check_incompatible_options_for_ci_rustc(rust: &Rust) -> Result<(), String> {
         remap_debuginfo: _,
         test_compare_mode: _,
         llvm_libunwind: _,
+        llvm_libzstd: _,
         control_flow_guard: _,
         ehcont_guard: _,
         new_symbol_mangling: _,