Can't compile for aarch64-pc-windows-msvc with the msvc toolchain during rustc bootstrap

[wesleywiser]

The issue seems to be that we're trying to pass lse.s to cl but cl doesn't support this. It looks like this regressed in 4af6bc7 (#416).

Perhaps this just needs to be adjusted to exclude msvc?

compiler-builtins/build.rs

Lines 495 to 501 in 31cf80b

	if target_arch == "aarch64" {
	// See below for why we're building these as separate libraries.
	build_aarch64_out_of_line_atomics_libraries(&src_dir, cfg);
	// Some run-time CPU feature detection is necessary, as well.
	sources.extend(&[("__aarch64_have_lse_atomics", "cpu_model.c")]);
	}

Repro:

D:\code> git clone https://github.com/rust-lang/compiler-builtins
D:\code> cd compiler-builtins
D:\code\compiler-builtins> set RUST_COMPILER_RT_ROOT=D:\code\rust\src\llvm-project\compiler-rt
D:\code\compiler-builtins> cargo +nightly build --target aarch64-pc-windows-msvc --features c
   Compiling compiler_builtins v0.1.47 (D:\code\compiler-builtins)
The following warnings were emitted during compilation:

warning: cl : Command line warning D9024 : unrecognized source file type 'D:\code\rust\src\llvm-project\compiler-rt\lib/builtins\aarch64/lse.S', object file assumed
warning: cl : Command line warning D9027 : source file 'D:\code\rust\src\llvm-project\compiler-rt\lib/builtins\aarch64/lse.S' ignored

error: failed to run custom build command for `compiler_builtins v0.1.47 (D:\code\compiler-builtins)`

Caused by:
  process didn't exit successfully: `D:\code\compiler-builtins\target\debug\build\compiler_builtins-974b0678a8f36634\build-script-build` (exit code: 1)
  --- stdout
  cargo:rerun-if-changed=build.rs
  cargo:compiler-rt=D:\code\compiler-builtins\compiler-rt
  cargo:rustc-cfg=feature="unstable"
  cargo:rerun-if-changed=D:\code\rust\src\llvm-project\compiler-rt\lib/builtins\aarch64/lse.S
  TARGET = Some("aarch64-pc-windows-msvc")
  OPT_LEVEL = Some("0")
  HOST = Some("x86_64-pc-windows-msvc")
  CC_aarch64-pc-windows-msvc = None
  CC_aarch64_pc_windows_msvc = None
  TARGET_CC = None
  CC = None
  CFLAGS_aarch64-pc-windows-msvc = None
  CFLAGS_aarch64_pc_windows_msvc = None
  TARGET_CFLAGS = None
  CFLAGS = None
  CRATE_CC_NO_DEFAULTS = None
  CARGO_CFG_TARGET_FEATURE = Some("fp,neon")
  DEBUG = Some("true")
  CC_aarch64-pc-windows-msvc = None
  CC_aarch64_pc_windows_msvc = None
  TARGET_CC = None
  CC = None
  CFLAGS_aarch64-pc-windows-msvc = None
  CFLAGS_aarch64_pc_windows_msvc = None
  TARGET_CFLAGS = None
  CFLAGS = None
  CRATE_CC_NO_DEFAULTS = None
  CARGO_CFG_TARGET_FEATURE = Some("fp,neon")
  running: "cl.exe" "-nologo" "-MD" "-Z7" "-Brepro" "-I" "D:\\code\\rust\\src\\llvm-project\\compiler-rt\\lib/builtins" "/Zl" "-D__func__=__FUNCTION__" "-DL_cas" "-DSIZE=1" "-DMODEL=1" "-FoD:\\code\\compiler-builtins\\target\\aarch64-pc-windows-msvc\\debug\\build\\compiler_builtins-8a216375ad68b403\\out\\lse.o" "-c" "D:\\code\\rust\\src\\llvm-project\\compiler-rt\\lib/builtins\\aarch64/lse.S"
  cargo:warning=cl : Command line warning D9024 : unrecognized source file type 'D:\code\rust\src\llvm-project\compiler-rt\lib/builtins\aarch64/lse.S', object file assumed
  cargo:warning=cl : Command line warning D9027 : source file 'D:\code\rust\src\llvm-project\compiler-rt\lib/builtins\aarch64/lse.S' ignored
  cl : Command line warning D9021 : no action performed
  exit code: 0
  AR_aarch64-pc-windows-msvc = None
  AR_aarch64_pc_windows_msvc = None
  TARGET_AR = None
  AR = None
  running: "lib.exe" "-out:D:\\code\\compiler-builtins\\target\\aarch64-pc-windows-msvc\\debug\\build\\compiler_builtins-8a216375ad68b403\\out\\liboutline_atomic_helper_cas1_relax.a" "-nologo" "D:\\code\\compiler-builtins\\target\\aarch64-pc-windows-msvc\\debug\\build\\compiler_builtins-8a216375ad68b403\\out\\lse.o"
  LINK : fatal error LNK1181: cannot open input file 'D:\code\compiler-builtins\target\aarch64-pc-windows-msvc\debug\build\compiler_builtins-8a216375ad68b403\out\lse.o'
  exit code: 1181

  --- stderr


  error occurred: Command "lib.exe" "-out:D:\\code\\compiler-builtins\\target\\aarch64-pc-windows-msvc\\debug\\build\\compiler_builtins-8a216375ad68b403\\out\\liboutline_atomic_helper_cas1_relax.a" "-nologo" "D:\\code\\compiler-builtins\\target\\aarch64-pc-windows-msvc\\debug\\build\\compiler_builtins-8a216375ad68b403\\out\\lse.o" with args "lib.exe" did not execute successfully (status code exit code: 1181).

[Amanieu]

These functions are needed, even on msvc targets, when the outlined atomics are used. Clang and GCC enable this by default, although rustc currently doesn't.

Is there a way to assemble lse.s in a way that works on msvc targets?

[wesleywiser]

I'm not aware of a way. There is an assembler included as part of the msvc toolchain however, I don't think it's compatible with the syntax used in lse.s.

Is it possible to disable outlined atomics for aarch64-pc-windows-msvc?

[Amanieu]

Looking through the GCC & Clang code:

• Clang only enables outlined atomics on Linux targets.
• GCC doesn't support aarch64 on windows.

So I think it's fine to just disable it for msvc (or windows) targets.