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.

config.example.toml

@@ -424,6 +424,11 @@
 # 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
 # =============================================================================

src/bootstrap/configure.py

@@ -44,10 +44,14 @@ o("optimize-tests", "rust.optimize-tests", "build tests with optimizations")
 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"):

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",
     }
 }
 
@@ -1622,6 +1623,7 @@ 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 +2008,7 @@ impl Config {
                 tests,
                 enzyme,
                 plugins,
-                ccache,
+                ccache: llvm_ccache,
                 static_libstdcpp,
                 libzstd,
                 ninja,
@@ -2029,13 +2031,7 @@ 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 => {}
-            }
+            ccache = ccache.or(llvm_ccache);
             set(&mut config.ninja_in_file, ninja);
             llvm_tests = tests;
             llvm_enzyme = enzyme;
@@ -2189,6 +2185,14 @@ 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");

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.",
+    },
 ];