Remove memcmp from spirv-std (#583)

crates/spirv-builder/src/lib.rs

@@ -247,8 +247,8 @@ fn invoke_rustc(builder: &SpirvBuilder, multimodule: bool) -> Result<PathBuf, Sp
  cargo.args(&[
  "build",
  "--message-format=json-render-diagnostics",
- "-Z",
- "build-std=core",
+ "-Zbuild-std=core",
+ "-Zbuild-std-features=compiler-builtins-mem",
  "--target",
  "spirv-unknown-unknown",
  ]);

crates/spirv-std/src/lib.rs

@@ -115,24 +115,3 @@ fn panic(_: &core::panic::PanicInfo<'_>) -> ! {
 #[cfg(all(not(test), target_arch = "spirv"))]
 #[lang = "eh_personality"]
 extern "C" fn rust_eh_personality() {}
-
-/// libcore requires a few external symbols to be defined:
-/// <https://github.com/rust-lang/rust/blob/c2bc344eb23d8c1d18e803b3f1e631cf99926fbb/library/core/src/lib.rs#L23-L27>
-/// TODO: This is copied from `compiler_builtins/mem.rs`. Can we use that one instead? The note in the above link says
-/// "[the symbols] can also be provided by the compiler-builtins crate". The memcpy in `compiler_builtins` is behind a
-/// "mem" feature flag - can we enable that somehow?
-/// <https://github.com/rust-lang/compiler-builtins/blob/eff506cd49b637f1ab5931625a33cef7e91fbbf6/src/mem.rs#L12-L13>
-#[allow(clippy::missing_safety_doc)]
-#[no_mangle]
-pub unsafe extern "C" fn memcmp(s1: *const u8, s2: *const u8, n: usize) -> i32 {
- let mut i = 0;
- while i < n {
- let a = *s1.add(i);
- let b = *s2.add(i);
- if a != b {
- return a as i32 - b as i32;
- }
- i += 1;
- }
- 0
-}

tests/src/main.rs

@@ -174,6 +174,7 @@ fn build_deps(deps_target_dir: &Path, codegen_backend_path: &Path, target: &str)
  "-p",
  "compiletests-deps-helper",
  "-Zbuild-std=core",
+ "-Zbuild-std-features=compiler-builtins-mem",
  &*format!("--target={}", target),
  ])
  .arg("--target-dir")