vendor/compiler_builtins/build.rs

   1 use std::env;
   2
   3 fn main() {
   4     println!("cargo:rerun-if-changed=build.rs");
   5
   6     let target = env::var("TARGET").unwrap();
   7     let cwd = env::current_dir().unwrap();
   8
   9     println!("cargo:compiler-rt={}", cwd.join("compiler-rt").display());
  10
  11     // Activate libm's unstable features to make full use of Nightly.
  12     println!("cargo:rustc-cfg=feature=\"unstable\"");
  13
  14     // Emscripten's runtime includes all the builtins
  15     if target.contains("emscripten") {
  16         return;
  17     }
  18
  19     // OpenBSD provides compiler_rt by default, use it instead of rebuilding it from source
  20     if target.contains("openbsd") {
  21         println!("cargo:rustc-link-search=native=/usr/lib");
  22         println!("cargo:rustc-link-lib=compiler_rt");
  23         return;
  24     }
  25
  26     // Forcibly enable memory intrinsics on wasm & SGX as we don't have a libc to
  27     // provide them.
  28     if (target.contains("wasm") && !target.contains("wasi"))
  29         || (target.contains("sgx") && target.contains("fortanix"))
  30         || target.contains("-none")
  31         || target.contains("nvptx")
  32     {
  33         println!("cargo:rustc-cfg=feature=\"mem\"");
  34     }
  35
  36     // These targets have hardware unaligned access support.
  37     if target.contains("x86_64")
  38         || target.contains("i686")
  39         || target.contains("aarch64")
  40         || target.contains("bpf")
  41     {
  42         println!("cargo:rustc-cfg=feature=\"mem-unaligned\"");
  43     }
  44
  45     // NOTE we are going to assume that llvm-target, what determines our codegen option, matches the
  46     // target triple. This is usually correct for our built-in targets but can break in presence of
  47     // custom targets, which can have arbitrary names.
  48     let llvm_target = target.split('-').collect::<Vec<_>>();
  49
  50     // Build missing intrinsics from compiler-rt C source code. If we're
  51     // mangling names though we assume that we're also in test mode so we don't
  52     // build anything and we rely on the upstream implementation of compiler-rt
  53     // functions
  54     if !cfg!(feature = "mangled-names") && cfg!(feature = "c") {
  55         // Don't use a C compiler for these targets:
  56         //
  57         // * wasm - clang for wasm is somewhat hard to come by and it's
  58         //   unlikely that the C is really that much better than our own Rust.
  59         // * nvptx - everything is bitcode, not compatible with mixed C/Rust
  60         // * riscv - the rust-lang/rust distribution container doesn't have a C
  61         //   compiler nor is cc-rs ready for compilation to riscv (at this
  62         //   time). This can probably be removed in the future
  63         if !target.contains("wasm") && !target.contains("nvptx") && !target.starts_with("riscv") {
  64             #[cfg(feature = "c")]
  65             c::compile(&llvm_target, &target);
  66         }
  67     }
  68
  69     // To compile intrinsics.rs for thumb targets, where there is no libc
  70     if llvm_target[0].starts_with("thumb") {
  71         println!("cargo:rustc-cfg=thumb")
  72     }
  73
  74     // compiler-rt `cfg`s away some intrinsics for thumbv6m and thumbv8m.base because
  75     // these targets do not have full Thumb-2 support but only original Thumb-1.
  76     // We have to cfg our code accordingly.
  77     if llvm_target[0] == "thumbv6m" || llvm_target[0] == "thumbv8m.base" {
  78         println!("cargo:rustc-cfg=thumb_1")
  79     }
  80
  81     // Only emit the ARM Linux atomic emulation on pre-ARMv6 architectures. This
  82     // includes the old androideabi. It is deprecated but it is available as a
  83     // rustc target (arm-linux-androideabi).
  84     if llvm_target[0] == "armv4t"
  85         || llvm_target[0] == "armv5te"
  86         || target == "arm-linux-androideabi"
  87     {
  88         println!("cargo:rustc-cfg=kernel_user_helpers")
  89     }
  90 }
  91
  92 #[cfg(feature = "c")]
  93 mod c {
  94     extern crate cc;
  95
  96     use std::collections::{BTreeMap, HashSet};
  97     use std::env;
  98     use std::fs::File;
  99     use std::io::Write;
 100     use std::path::{Path, PathBuf};
 101
 102     struct Sources {
 103         // SYMBOL -> PATH TO SOURCE
 104         map: BTreeMap<&'static str, &'static str>,
 105     }
 106
 107     impl Sources {
 108         fn new() -> Sources {
 109             Sources {
 110                 map: BTreeMap::new(),
 111             }
 112         }
 113
 114         fn extend(&mut self, sources: &[(&'static str, &'static str)]) {
 115             // NOTE Some intrinsics have both a generic implementation (e.g.
 116             // `floatdidf.c`) and an arch optimized implementation
 117             // (`x86_64/floatdidf.c`). In those cases, we keep the arch optimized
 118             // implementation and discard the generic implementation. If we don't
 119             // and keep both implementations, the linker will yell at us about
 120             // duplicate symbols!
 121             for (symbol, src) in sources {
 122                 if src.contains("/") {
 123                     // Arch-optimized implementation (preferred)
 124                     self.map.insert(symbol, src);
 125                 } else {
 126                     // Generic implementation
 127                     if !self.map.contains_key(symbol) {
 128                         self.map.insert(symbol, src);
 129                     }
 130                 }
 131             }
 132         }
 133
 134         fn remove(&mut self, symbols: &[&str]) {
 135             for symbol in symbols {
 136                 self.map.remove(*symbol).unwrap();
 137             }
 138         }
 139     }
 140
 141     /// Compile intrinsics from the compiler-rt C source code
 142     pub fn compile(llvm_target: &[&str], target: &String) {
 143         let target_arch = env::var("CARGO_CFG_TARGET_ARCH").unwrap();
 144         let target_env = env::var("CARGO_CFG_TARGET_ENV").unwrap();
 145         let target_os = env::var("CARGO_CFG_TARGET_OS").unwrap();
 146         let target_vendor = env::var("CARGO_CFG_TARGET_VENDOR").unwrap();
 147         let mut consider_float_intrinsics = true;
 148         let cfg = &mut cc::Build::new();
 149
 150         // AArch64 GCCs exit with an error condition when they encounter any kind of floating point
 151         // code if the `nofp` and/or `nosimd` compiler flags have been set.
 152         //
 153         // Therefore, evaluate if those flags are present and set a boolean that causes any
 154         // compiler-rt intrinsics that contain floating point source to be excluded for this target.
 155         if target_arch == "aarch64" {
 156             let cflags_key = String::from("CFLAGS_") + &(target.to_owned().replace("-", "_"));
 157             if let Ok(cflags_value) = env::var(cflags_key) {
 158                 if cflags_value.contains("+nofp") || cflags_value.contains("+nosimd") {
 159                     consider_float_intrinsics = false;
 160                 }
 161             }
 162         }
 163
 164         cfg.warnings(false);
 165
 166         if target_env == "msvc" {
 167             // Don't pull in extra libraries on MSVC
 168             cfg.flag("/Zl");
 169
 170             // Emulate C99 and C++11's __func__ for MSVC prior to 2013 CTP
 171             cfg.define("__func__", Some("__FUNCTION__"));
 172         } else {
 173             // Turn off various features of gcc and such, mostly copying
 174             // compiler-rt's build system already
 175             cfg.flag("-fno-builtin");
 176             cfg.flag("-fvisibility=hidden");
 177             cfg.flag("-ffreestanding");
 178             // Avoid the following warning appearing once **per file**:
 179             // clang: warning: optimization flag '-fomit-frame-pointer' is not supported for target 'armv7' [-Wignored-optimization-argument]
 180             //
 181             // Note that compiler-rt's build system also checks
 182             //
 183             // `check_cxx_compiler_flag(-fomit-frame-pointer COMPILER_RT_HAS_FOMIT_FRAME_POINTER_FLAG)`
 184             //
 185             // in https://github.com/rust-lang/compiler-rt/blob/c8fbcb3/cmake/config-ix.cmake#L19.
 186             cfg.flag_if_supported("-fomit-frame-pointer");
 187             cfg.define("VISIBILITY_HIDDEN", None);
 188         }
 189
 190         let mut sources = Sources::new();
 191         sources.extend(&[
 192             ("__absvdi2", "absvdi2.c"),
 193             ("__absvsi2", "absvsi2.c"),
 194             ("__addvdi3", "addvdi3.c"),
 195             ("__addvsi3", "addvsi3.c"),
 196             ("apple_versioning", "apple_versioning.c"),
 197             ("__clzdi2", "clzdi2.c"),
 198             ("__clzsi2", "clzsi2.c"),
 199             ("__cmpdi2", "cmpdi2.c"),
 200             ("__ctzdi2", "ctzdi2.c"),
 201             ("__ctzsi2", "ctzsi2.c"),
 202             ("__int_util", "int_util.c"),
 203             ("__mulvdi3", "mulvdi3.c"),
 204             ("__mulvsi3", "mulvsi3.c"),
 205             ("__negdi2", "negdi2.c"),
 206             ("__negvdi2", "negvdi2.c"),
 207             ("__negvsi2", "negvsi2.c"),
 208             ("__paritydi2", "paritydi2.c"),
 209             ("__paritysi2", "paritysi2.c"),
 210             ("__popcountdi2", "popcountdi2.c"),
 211             ("__popcountsi2", "popcountsi2.c"),
 212             ("__subvdi3", "subvdi3.c"),
 213             ("__subvsi3", "subvsi3.c"),
 214             ("__ucmpdi2", "ucmpdi2.c"),
 215         ]);
 216
 217         if consider_float_intrinsics {
 218             sources.extend(&[
 219                 ("__divdc3", "divdc3.c"),
 220                 ("__divsc3", "divsc3.c"),
 221                 ("__divxc3", "divxc3.c"),
 222                 ("__extendhfsf2", "extendhfsf2.c"),
 223                 ("__muldc3", "muldc3.c"),
 224                 ("__mulsc3", "mulsc3.c"),
 225                 ("__mulxc3", "mulxc3.c"),
 226                 ("__negdf2", "negdf2.c"),
 227                 ("__negsf2", "negsf2.c"),
 228                 ("__powixf2", "powixf2.c"),
 229                 ("__truncdfhf2", "truncdfhf2.c"),
 230                 ("__truncsfhf2", "truncsfhf2.c"),
 231             ]);
 232         }
 233
 234         // When compiling in rustbuild (the rust-lang/rust repo) this library
 235         // also needs to satisfy intrinsics that jemalloc or C in general may
 236         // need, so include a few more that aren't typically needed by
 237         // LLVM/Rust.
 238         if cfg!(feature = "rustbuild") {
 239             sources.extend(&[("__ffsdi2", "ffsdi2.c")]);
 240         }
 241
 242         // On iOS and 32-bit OSX these are all just empty intrinsics, no need to
 243         // include them.
 244         if target_os != "ios"
 245             && target_os != "watchos"
 246             && (target_vendor != "apple" || target_arch != "x86")
 247         {
 248             sources.extend(&[
 249                 ("__absvti2", "absvti2.c"),
 250                 ("__addvti3", "addvti3.c"),
 251                 ("__clzti2", "clzti2.c"),
 252                 ("__cmpti2", "cmpti2.c"),
 253                 ("__ctzti2", "ctzti2.c"),
 254                 ("__ffsti2", "ffsti2.c"),
 255                 ("__mulvti3", "mulvti3.c"),
 256                 ("__negti2", "negti2.c"),
 257                 ("__parityti2", "parityti2.c"),
 258                 ("__popcountti2", "popcountti2.c"),
 259                 ("__subvti3", "subvti3.c"),
 260                 ("__ucmpti2", "ucmpti2.c"),
 261             ]);
 262
 263             if consider_float_intrinsics {
 264                 sources.extend(&[("__negvti2", "negvti2.c")]);
 265             }
 266         }
 267
 268         if target_vendor == "apple" {
 269             sources.extend(&[
 270                 ("atomic_flag_clear", "atomic_flag_clear.c"),
 271                 ("atomic_flag_clear_explicit", "atomic_flag_clear_explicit.c"),
 272                 ("atomic_flag_test_and_set", "atomic_flag_test_and_set.c"),
 273                 (
 274                     "atomic_flag_test_and_set_explicit",
 275                     "atomic_flag_test_and_set_explicit.c",
 276                 ),
 277                 ("atomic_signal_fence", "atomic_signal_fence.c"),
 278                 ("atomic_thread_fence", "atomic_thread_fence.c"),
 279             ]);
 280         }
 281
 282         if target_env == "msvc" {
 283             if target_arch == "x86_64" {
 284                 sources.extend(&[
 285                     ("__floatdisf", "x86_64/floatdisf.c"),
 286                     ("__floatdixf", "x86_64/floatdixf.c"),
 287                 ]);
 288             }
 289         } else {
 290             // None of these seem to be used on x86_64 windows, and they've all
 291             // got the wrong ABI anyway, so we want to avoid them.
 292             if target_os != "windows" {
 293                 if target_arch == "x86_64" {
 294                     sources.extend(&[
 295                         ("__floatdisf", "x86_64/floatdisf.c"),
 296                         ("__floatdixf", "x86_64/floatdixf.c"),
 297                         ("__floatundidf", "x86_64/floatundidf.S"),
 298                         ("__floatundisf", "x86_64/floatundisf.S"),
 299                         ("__floatundixf", "x86_64/floatundixf.S"),
 300                     ]);
 301                 }
 302             }
 303
 304             if target_arch == "x86" {
 305                 sources.extend(&[
 306                     ("__ashldi3", "i386/ashldi3.S"),
 307                     ("__ashrdi3", "i386/ashrdi3.S"),
 308                     ("__divdi3", "i386/divdi3.S"),
 309                     ("__floatdidf", "i386/floatdidf.S"),
 310                     ("__floatdisf", "i386/floatdisf.S"),
 311                     ("__floatdixf", "i386/floatdixf.S"),
 312                     ("__floatundidf", "i386/floatundidf.S"),
 313                     ("__floatundisf", "i386/floatundisf.S"),
 314                     ("__floatundixf", "i386/floatundixf.S"),
 315                     ("__lshrdi3", "i386/lshrdi3.S"),
 316                     ("__moddi3", "i386/moddi3.S"),
 317                     ("__muldi3", "i386/muldi3.S"),
 318                     ("__udivdi3", "i386/udivdi3.S"),
 319                     ("__umoddi3", "i386/umoddi3.S"),
 320                 ]);
 321             }
 322         }
 323
 324         if target_arch == "arm"
 325             && target_os != "ios"
 326             && target_os != "watchos"
 327             && target_env != "msvc"
 328         {
 329             sources.extend(&[
 330                 ("__aeabi_div0", "arm/aeabi_div0.c"),
 331                 ("__aeabi_drsub", "arm/aeabi_drsub.c"),
 332                 ("__aeabi_frsub", "arm/aeabi_frsub.c"),
 333                 ("__bswapdi2", "arm/bswapdi2.S"),
 334                 ("__bswapsi2", "arm/bswapsi2.S"),
 335                 ("__clzdi2", "arm/clzdi2.S"),
 336                 ("__clzsi2", "arm/clzsi2.S"),
 337                 ("__divmodsi4", "arm/divmodsi4.S"),
 338                 ("__divsi3", "arm/divsi3.S"),
 339                 ("__modsi3", "arm/modsi3.S"),
 340                 ("__switch16", "arm/switch16.S"),
 341                 ("__switch32", "arm/switch32.S"),
 342                 ("__switch8", "arm/switch8.S"),
 343                 ("__switchu8", "arm/switchu8.S"),
 344                 ("__sync_synchronize", "arm/sync_synchronize.S"),
 345                 ("__udivmodsi4", "arm/udivmodsi4.S"),
 346                 ("__udivsi3", "arm/udivsi3.S"),
 347                 ("__umodsi3", "arm/umodsi3.S"),
 348             ]);
 349
 350             if target_os == "freebsd" {
 351                 sources.extend(&[("__clear_cache", "clear_cache.c")]);
 352             }
 353
 354             // First of all aeabi_cdcmp and aeabi_cfcmp are never called by LLVM.
 355             // Second are little-endian only, so build fail on big-endian targets.
 356             // Temporally workaround: exclude these files for big-endian targets.
 357             if !llvm_target[0].starts_with("thumbeb") && !llvm_target[0].starts_with("armeb") {
 358                 sources.extend(&[
 359                     ("__aeabi_cdcmp", "arm/aeabi_cdcmp.S"),
 360                     ("__aeabi_cdcmpeq_check_nan", "arm/aeabi_cdcmpeq_check_nan.c"),
 361                     ("__aeabi_cfcmp", "arm/aeabi_cfcmp.S"),
 362                     ("__aeabi_cfcmpeq_check_nan", "arm/aeabi_cfcmpeq_check_nan.c"),
 363                 ]);
 364             }
 365         }
 366
 367         if llvm_target[0] == "armv7" {
 368             sources.extend(&[
 369                 ("__sync_fetch_and_add_4", "arm/sync_fetch_and_add_4.S"),
 370                 ("__sync_fetch_and_add_8", "arm/sync_fetch_and_add_8.S"),
 371                 ("__sync_fetch_and_and_4", "arm/sync_fetch_and_and_4.S"),
 372                 ("__sync_fetch_and_and_8", "arm/sync_fetch_and_and_8.S"),
 373                 ("__sync_fetch_and_max_4", "arm/sync_fetch_and_max_4.S"),
 374                 ("__sync_fetch_and_max_8", "arm/sync_fetch_and_max_8.S"),
 375                 ("__sync_fetch_and_min_4", "arm/sync_fetch_and_min_4.S"),
 376                 ("__sync_fetch_and_min_8", "arm/sync_fetch_and_min_8.S"),
 377                 ("__sync_fetch_and_nand_4", "arm/sync_fetch_and_nand_4.S"),
 378                 ("__sync_fetch_and_nand_8", "arm/sync_fetch_and_nand_8.S"),
 379                 ("__sync_fetch_and_or_4", "arm/sync_fetch_and_or_4.S"),
 380                 ("__sync_fetch_and_or_8", "arm/sync_fetch_and_or_8.S"),
 381                 ("__sync_fetch_and_sub_4", "arm/sync_fetch_and_sub_4.S"),
 382                 ("__sync_fetch_and_sub_8", "arm/sync_fetch_and_sub_8.S"),
 383                 ("__sync_fetch_and_umax_4", "arm/sync_fetch_and_umax_4.S"),
 384                 ("__sync_fetch_and_umax_8", "arm/sync_fetch_and_umax_8.S"),
 385                 ("__sync_fetch_and_umin_4", "arm/sync_fetch_and_umin_4.S"),
 386                 ("__sync_fetch_and_umin_8", "arm/sync_fetch_and_umin_8.S"),
 387                 ("__sync_fetch_and_xor_4", "arm/sync_fetch_and_xor_4.S"),
 388                 ("__sync_fetch_and_xor_8", "arm/sync_fetch_and_xor_8.S"),
 389             ]);
 390         }
 391
 392         if llvm_target.last().unwrap().ends_with("eabihf") {
 393             if !llvm_target[0].starts_with("thumbv7em")
 394                 && !llvm_target[0].starts_with("thumbv8m.main")
 395             {
 396                 // The FPU option chosen for these architectures in cc-rs, ie:
 397                 //     -mfpu=fpv4-sp-d16 for thumbv7em
 398                 //     -mfpu=fpv5-sp-d16 for thumbv8m.main
 399                 // do not support double precision floating points conversions so the files
 400                 // that include such instructions are not included for these targets.
 401                 sources.extend(&[
 402                     ("__fixdfsivfp", "arm/fixdfsivfp.S"),
 403                     ("__fixunsdfsivfp", "arm/fixunsdfsivfp.S"),
 404                     ("__floatsidfvfp", "arm/floatsidfvfp.S"),
 405                     ("__floatunssidfvfp", "arm/floatunssidfvfp.S"),
 406                 ]);
 407             }
 408
 409             sources.extend(&[
 410                 ("__fixsfsivfp", "arm/fixsfsivfp.S"),
 411                 ("__fixunssfsivfp", "arm/fixunssfsivfp.S"),
 412                 ("__floatsisfvfp", "arm/floatsisfvfp.S"),
 413                 ("__floatunssisfvfp", "arm/floatunssisfvfp.S"),
 414                 ("__floatunssisfvfp", "arm/floatunssisfvfp.S"),
 415                 ("__restore_vfp_d8_d15_regs", "arm/restore_vfp_d8_d15_regs.S"),
 416                 ("__save_vfp_d8_d15_regs", "arm/save_vfp_d8_d15_regs.S"),
 417                 ("__negdf2vfp", "arm/negdf2vfp.S"),
 418                 ("__negsf2vfp", "arm/negsf2vfp.S"),
 419             ]);
 420         }
 421
 422         if target_arch == "aarch64" && consider_float_intrinsics {
 423             sources.extend(&[
 424                 ("__comparetf2", "comparetf2.c"),
 425                 ("__extenddftf2", "extenddftf2.c"),
 426                 ("__extendsftf2", "extendsftf2.c"),
 427                 ("__fixtfdi", "fixtfdi.c"),
 428                 ("__fixtfsi", "fixtfsi.c"),
 429                 ("__fixtfti", "fixtfti.c"),
 430                 ("__fixunstfdi", "fixunstfdi.c"),
 431                 ("__fixunstfsi", "fixunstfsi.c"),
 432                 ("__fixunstfti", "fixunstfti.c"),
 433                 ("__floatditf", "floatditf.c"),
 434                 ("__floatsitf", "floatsitf.c"),
 435                 ("__floatunditf", "floatunditf.c"),
 436                 ("__floatunsitf", "floatunsitf.c"),
 437                 ("__trunctfdf2", "trunctfdf2.c"),
 438                 ("__trunctfsf2", "trunctfsf2.c"),
 439                 ("__addtf3", "addtf3.c"),
 440                 ("__multf3", "multf3.c"),
 441                 ("__subtf3", "subtf3.c"),
 442                 ("__divtf3", "divtf3.c"),
 443                 ("__powitf2", "powitf2.c"),
 444                 ("__fe_getround", "fp_mode.c"),
 445                 ("__fe_raise_inexact", "fp_mode.c"),
 446             ]);
 447
 448             if target_os != "windows" {
 449                 sources.extend(&[("__multc3", "multc3.c")]);
 450             }
 451         }
 452
 453         if target_arch == "mips" {
 454             sources.extend(&[("__bswapsi2", "bswapsi2.c")]);
 455         }
 456
 457         if target_arch == "mips64" {
 458             sources.extend(&[
 459                 ("__extenddftf2", "extenddftf2.c"),
 460                 ("__netf2", "comparetf2.c"),
 461                 ("__addtf3", "addtf3.c"),
 462                 ("__multf3", "multf3.c"),
 463                 ("__subtf3", "subtf3.c"),
 464                 ("__fixtfsi", "fixtfsi.c"),
 465                 ("__floatsitf", "floatsitf.c"),
 466                 ("__fixunstfsi", "fixunstfsi.c"),
 467                 ("__floatunsitf", "floatunsitf.c"),
 468                 ("__fe_getround", "fp_mode.c"),
 469                 ("__divtf3", "divtf3.c"),
 470                 ("__trunctfdf2", "trunctfdf2.c"),
 471             ]);
 472         }
 473
 474         // Remove the assembly implementations that won't compile for the target
 475         if llvm_target[0] == "thumbv6m" || llvm_target[0] == "thumbv8m.base" {
 476             let mut to_remove = Vec::new();
 477             for (k, v) in sources.map.iter() {
 478                 if v.ends_with(".S") {
 479                     to_remove.push(*k);
 480                 }
 481             }
 482             sources.remove(&to_remove);
 483
 484             // But use some generic implementations where possible
 485             sources.extend(&[("__clzdi2", "clzdi2.c"), ("__clzsi2", "clzsi2.c")])
 486         }
 487
 488         if llvm_target[0] == "thumbv7m" || llvm_target[0] == "thumbv7em" {
 489             sources.remove(&["__aeabi_cdcmp", "__aeabi_cfcmp"]);
 490         }
 491
 492         // When compiling the C code we require the user to tell us where the
 493         // source code is, and this is largely done so when we're compiling as
 494         // part of rust-lang/rust we can use the same llvm-project repository as
 495         // rust-lang/rust.
 496         let root = match env::var_os("RUST_COMPILER_RT_ROOT") {
 497             Some(s) => PathBuf::from(s),
 498             None => panic!("RUST_COMPILER_RT_ROOT is not set"),
 499         };
 500         if !root.exists() {
 501             panic!("RUST_COMPILER_RT_ROOT={} does not exist", root.display());
 502         }
 503
 504         // Support deterministic builds by remapping the __FILE__ prefix if the
 505         // compiler supports it.  This fixes the nondeterminism caused by the
 506         // use of that macro in lib/builtins/int_util.h in compiler-rt.
 507         cfg.flag_if_supported(&format!("-ffile-prefix-map={}=.", root.display()));
 508
 509         // Include out-of-line atomics for aarch64, which are all generated by supplying different
 510         // sets of flags to the same source file.
 511         // Note: Out-of-line aarch64 atomics are not supported by the msvc toolchain (#430).
 512         let src_dir = root.join("lib/builtins");
 513         if target_arch == "aarch64" && target_env != "msvc" {
 514             // See below for why we're building these as separate libraries.
 515             build_aarch64_out_of_line_atomics_libraries(&src_dir, cfg);
 516
 517             // Some run-time CPU feature detection is necessary, as well.
 518             sources.extend(&[("__aarch64_have_lse_atomics", "cpu_model.c")]);
 519         }
 520
 521         let mut added_sources = HashSet::new();
 522         for (sym, src) in sources.map.iter() {
 523             let src = src_dir.join(src);
 524             if added_sources.insert(src.clone()) {
 525                 cfg.file(&src);
 526                 println!("cargo:rerun-if-changed={}", src.display());
 527             }
 528             println!("cargo:rustc-cfg={}=\"optimized-c\"", sym);
 529         }
 530
 531         cfg.compile("libcompiler-rt.a");
 532     }
 533
 534     fn build_aarch64_out_of_line_atomics_libraries(builtins_dir: &Path, cfg: &mut cc::Build) {
 535         let out_dir = PathBuf::from(env::var("OUT_DIR").unwrap());
 536         let outlined_atomics_file = builtins_dir.join("aarch64/lse.S");
 537         println!("cargo:rerun-if-changed={}", outlined_atomics_file.display());
 538
 539         cfg.include(&builtins_dir);
 540
 541         for instruction_type in &["cas", "swp", "ldadd", "ldclr", "ldeor", "ldset"] {
 542             for size in &[1, 2, 4, 8, 16] {
 543                 if *size == 16 && *instruction_type != "cas" {
 544                     continue;
 545                 }
 546
 547                 for (model_number, model_name) in
 548                     &[(1, "relax"), (2, "acq"), (3, "rel"), (4, "acq_rel")]
 549                 {
 550                     // The original compiler-rt build system compiles the same
 551                     // source file multiple times with different compiler
 552                     // options. Here we do something slightly different: we
 553                     // create multiple .S files with the proper #defines and
 554                     // then include the original file.
 555                     //
 556                     // This is needed because the cc crate doesn't allow us to
 557                     // override the name of object files and libtool requires
 558                     // all objects in an archive to have unique names.
 559                     let path =
 560                         out_dir.join(format!("lse_{}{}_{}.S", instruction_type, size, model_name));
 561                     let mut file = File::create(&path).unwrap();
 562                     writeln!(file, "#define L_{}", instruction_type).unwrap();
 563                     writeln!(file, "#define SIZE {}", size).unwrap();
 564                     writeln!(file, "#define MODEL {}", model_number).unwrap();
 565                     writeln!(
 566                         file,
 567                         "#include \"{}\"",
 568                         outlined_atomics_file.canonicalize().unwrap().display()
 569                     )
 570                     .unwrap();
 571                     drop(file);
 572                     cfg.file(path);
 573
 574                     let sym = format!("__aarch64_{}{}_{}", instruction_type, size, model_name);
 575                     println!("cargo:rustc-cfg={}=\"optimized-c\"", sym);
 576                 }
 577             }
 578         }
 579     }
 580 }