Mimalloc support as a separate config.toml option.

Remove misleading OSX from config.toml option comments as
it is not really supported.

Cargo.lock

@@ -1222,6 +1222,12 @@ dependencies = [
  "rustc-std-workspace-core",
 ]
 
+[[package]]
+name = "fs_extra"
+version = "1.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2022715d62ab30faffd124d40b76f4134a550a87792276512b18d63272333394"
+
 [[package]]
 name = "fst"
 version = "0.3.5"
@@ -1612,6 +1618,17 @@ version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "dc6f3ad7b9d11a0c00842ff8de1b60ee58661048eb8049ed33c73594f359d7e6"
 
+[[package]]
+name = "jemalloc-sys"
+version = "0.3.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0d3b9f3f5c9b31aa0f5ed3260385ac205db665baa41d49bb8338008ae94ede45"
+dependencies = [
+ "cc",
+ "fs_extra",
+ "libc",
+]
+
 [[package]]
 name = "jobserver"
 version = "0.1.21"
@@ -3405,6 +3422,7 @@ checksum = "08d43f7aa6b08d49f382cde6a7982047c3426db949b1424bc4b7ec9ae12c6ce2"
 name = "rustc-main"
 version = "0.0.0"
 dependencies = [
+ "jemalloc-sys",
  "libmimalloc-sys",
  "rustc_codegen_ssa",
  "rustc_driver",

compiler/rustc/Cargo.toml

@@ -11,18 +11,19 @@ rustc_driver = { path = "../rustc_driver" }
 # crate is intended to be used by codegen backends, which may not be in-tree.
 rustc_codegen_ssa = { path = "../rustc_codegen_ssa" }
 
-#[dependencies.jemalloc-sys]
-#version = '0.3.0'
-#optional = true
-#features = ['unprefixed_malloc_on_supported_platforms']
+[dependencies.jemalloc-sys]
+version = '0.3.0'
+optional = true
+features = ['unprefixed_malloc_on_supported_platforms']
 
 [dependencies.libmimalloc-sys]
-version = "0.1.20"
+version = '0.1.20'
 optional = true
 default-features = false
-features = ["extended", "override"]
+features = ['extended', 'override']
 
 [features]
-jemalloc = ['libmimalloc-sys']
+jemalloc = ['jemalloc-sys']
+mimalloc = ['libmimalloc-sys']
 llvm = ['rustc_driver/llvm']
 max_level_info = ['rustc_driver/max_level_info']

compiler/rustc/src/main.rs

@@ -7,6 +7,33 @@ fn main() {
     // dynamic libraries. That means to pull in jemalloc we need to actually
     // reference allocation symbols one way or another (as this file is the only
     // object code in the rustc executable).
+    #[cfg(feature = "jemalloc-sys")]
+    {
+        use std::os::raw::{c_int, c_void};
+
+        #[used]
+        static _F1: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::calloc;
+        #[used]
+        static _F2: unsafe extern "C" fn(*mut *mut c_void, usize, usize) -> c_int =
+            jemalloc_sys::posix_memalign;
+        #[used]
+        static _F3: unsafe extern "C" fn(usize, usize) -> *mut c_void = jemalloc_sys::aligned_alloc;
+        #[used]
+        static _F4: unsafe extern "C" fn(usize) -> *mut c_void = jemalloc_sys::malloc;
+        #[used]
+        static _F5: unsafe extern "C" fn(*mut c_void, usize) -> *mut c_void = jemalloc_sys::realloc;
+        #[used]
+        static _F6: unsafe extern "C" fn(*mut c_void) = jemalloc_sys::free;
+    }
+
+    // Pull in mimalloc when enabled.
+    //
+    // Note that we're pulling in a static copy of mimalloc which means that to
+    // pull it in we need to actually reference its symbols for it to get
+    // linked. The two crates we link to here, std and rustc_driver, are both
+    // dynamic libraries. That means to pull in mimalloc we need to actually
+    // reference allocation symbols one way or another (as this file is the only
+    // object code in the rustc executable).
     #[cfg(feature = "libmimalloc-sys")]
     {
         use std::os::raw::{c_int, c_void};

config.toml.example

@@ -535,9 +535,13 @@ changelog-seen = 2
 # Map debuginfo paths to `/rust/$sha/...`, generally only set for releases
 #remap-debuginfo = false
 
-# Link the compiler against `jemalloc`, where on Linux and OSX it should
-# override the default allocator for rustc and LLVM.
+# Link the compiler against `jemalloc`, where on Linux it should override
+# the default allocator for rustc and LLVM.
 #jemalloc = false
+#
+# Link the compiler against `mimalloc`, where on Linux it should override
+# the default allocator for rustc and LLVM.
+#mimalloc = false
 
 # Run tests in various test suites with the "nll compare mode" in addition to
 # running the tests in normal mode. Largely only used on CI and during local

src/bootstrap/config.rs

@@ -142,6 +142,7 @@ pub struct Config {
     pub targets: Vec<TargetSelection>,
     pub local_rebuild: bool,
     pub jemalloc: bool,
+    pub mimalloc: bool,
     pub control_flow_guard: bool,
 
     // dist misc
@@ -497,6 +498,7 @@ struct Rust {
     thin_lto_import_instr_limit: Option<u32>,
     remap_debuginfo: Option<bool>,
     jemalloc: Option<bool>,
+    mimalloc: Option<bool>,
     test_compare_mode: Option<bool>,
     llvm_libunwind: Option<String>,
     control_flow_guard: Option<bool>,
@@ -849,6 +851,7 @@ impl Config {
             set(&mut config.codegen_tests, rust.codegen_tests);
             set(&mut config.rust_rpath, rust.rpath);
             set(&mut config.jemalloc, rust.jemalloc);
+            set(&mut config.mimalloc, rust.mimalloc);
             set(&mut config.test_compare_mode, rust.test_compare_mode);
             config.llvm_libunwind = rust
                 .llvm_libunwind

src/bootstrap/lib.rs

@@ -567,6 +567,9 @@ impl Build {
         if self.config.jemalloc {
             features.push_str("jemalloc");
         }
+        if self.config.mimalloc {
+            features.push_str("mimalloc");
+        }
         if self.config.llvm_enabled() {
             features.push_str(" llvm");
         }