Rollup merge of #136941 - Kobzol:ccache-build, r=onur-ozkan

Move `llvm.ccache` to `build.ccache`

(S)ccache can be useful for more things that just LLVM. For example, we will soon want to use it also for GCC, and theoretically also for building stage0 Rust tools (#136921, https://rust-lang.zulipchat.com/#narrow/channel/242791-t-infra/topic/Using.20sccache.20for.20Rust).

r? ``@onur-ozkan``

Author: workingjubilee

Diff for: config.example.toml

@@ -87,10 +87,6 @@
 # Whether to build LLVM with support for it's gpu offload runtime.
 #offload = false
 
-# Indicates whether ccache is used when building LLVM. Set to `true` to use the first `ccache` in
-# PATH, or set an absolute path to use a specific version.
-#ccache = false
-
 # When true, link libstdc++ statically into the rustc_llvm.
 # This is useful if you don't want to use the dynamic version of that
 # library provided by LLVM.
@@ -424,6 +420,11 @@
 # What custom diff tool to use for displaying compiletest tests.
 #compiletest-diff-tool = <none>
 
+# Indicates whether ccache is used when building certain artifacts (e.g. LLVM).
+# Set to `true` to use the first `ccache` in PATH, or set an absolute path to use
+# a specific version.
+#ccache = false
+
 # =============================================================================
 # General install configuration options
 # =============================================================================

Diff for: src/bootstrap/configure.py

@@ -44,10 +44,14 @@ def v(*args):
 o("verbose-tests", "rust.verbose-tests", "enable verbose output when running tests")
 o(
     "ccache",
-    "llvm.ccache",
-    "invoke gcc/clang via ccache to reuse object files between builds",
+    "build.ccache",
+    "invoke gcc/clang/rustc via ccache to reuse object files between builds",
+)
+o(
+    "sccache",
+    None,
+    "invoke gcc/clang/rustc via sccache to reuse object files between builds",
 )
-o("sccache", None, "invoke gcc/clang via sccache to reuse object files between builds")
 o("local-rust", None, "use an installed rustc rather than downloading a snapshot")
 v("local-rust-root", None, "set prefix for local rust binary")
 o(
@@ -510,7 +514,7 @@ def apply_args(known_args, option_checking, config):
         build_triple = build(known_args)
 
         if option.name == "sccache":
-            set("llvm.ccache", "sccache", config)
+            set("build.ccache", "sccache", config)
         elif option.name == "local-rust":
             for path in os.environ["PATH"].split(os.pathsep):
                 if os.path.exists(path + "/rustc"):

Diff for: src/bootstrap/src/core/config/config.rs

@@ -935,6 +935,7 @@ define_config! {
         optimized_compiler_builtins: Option<bool> = "optimized-compiler-builtins",
         jobs: Option<u32> = "jobs",
         compiletest_diff_tool: Option<String> = "compiletest-diff-tool",
+        ccache: Option<StringOrBool> = "ccache",
     }
 }
 
@@ -961,6 +962,7 @@ define_config! {
         tests: Option<bool> = "tests",
         enzyme: Option<bool> = "enzyme",
         plugins: Option<bool> = "plugins",
+        // FIXME: Remove this field at Q2 2025, it has been replaced by build.ccache
         ccache: Option<StringOrBool> = "ccache",
         static_libstdcpp: Option<bool> = "static-libstdcpp",
         libzstd: Option<bool> = "libzstd",
@@ -1622,6 +1624,7 @@ impl Config {
             optimized_compiler_builtins,
             jobs,
             compiletest_diff_tool,
+            mut ccache,
         } = toml.build.unwrap_or_default();
 
         config.jobs = Some(threads_from_config(flags.jobs.unwrap_or(jobs.unwrap_or(0))));
@@ -2006,7 +2009,7 @@ impl Config {
                 tests,
                 enzyme,
                 plugins,
-                ccache,
+                ccache: llvm_ccache,
                 static_libstdcpp,
                 libzstd,
                 ninja,
@@ -2029,13 +2032,11 @@ impl Config {
                 download_ci_llvm,
                 build_config,
             } = llvm;
-            match ccache {
-                Some(StringOrBool::String(ref s)) => config.ccache = Some(s.to_string()),
-                Some(StringOrBool::Bool(true)) => {
-                    config.ccache = Some("ccache".to_string());
-                }
-                Some(StringOrBool::Bool(false)) | None => {}
+            if llvm_ccache.is_some() {
+                eprintln!("Warning: llvm.ccache is deprecated. Use build.ccache instead.");
             }
+
+            ccache = ccache.or(llvm_ccache);
             set(&mut config.ninja_in_file, ninja);
             llvm_tests = tests;
             llvm_enzyme = enzyme;
@@ -2189,6 +2190,14 @@ impl Config {
             }
         }
 
+        match ccache {
+            Some(StringOrBool::String(ref s)) => config.ccache = Some(s.to_string()),
+            Some(StringOrBool::Bool(true)) => {
+                config.ccache = Some("ccache".to_string());
+            }
+            Some(StringOrBool::Bool(false)) | None => {}
+        }
+
         if config.llvm_from_ci {
             let triple = &config.build.triple;
             let ci_llvm_bin = config.ci_llvm_root().join("bin");

Diff for: src/bootstrap/src/utils/change_tracker.rs

@@ -345,4 +345,9 @@ pub const CONFIG_CHANGE_HISTORY: &[ChangeInfo] = &[
         severity: ChangeSeverity::Info,
         summary: "Rustdoc now respects the value of rust.lto.",
     },
+    ChangeInfo {
+        change_id: 136941,
+        severity: ChangeSeverity::Info,
+        summary: "The llvm.ccache option has moved to build.ccache. llvm.ccache is now deprecated.",
+    },
 ];