Refactor stdsimd

This commit:

* renames `coresimd` to `core_arch` and `stdsimd` to `std_detect`

* `std_detect` does no longer depend on `core_arch` - it is a freestanding
  `no_std` library that only depends on `core` - it is renamed to `std_detect`

* moves the top-level coresimd and stdsimd directories into the appropriate
  crates/... directories - this simplifies creating crate.io releases of these crates

* moves the top-level `coresimd` and `stdsimd` sub-directories into their
  corresponding crates in `crates/{core_arch, std_detect}`.

1 files changed, 9 insertions, 0 deletions

diff --git a/library/stdarch/crates/std_detect/src/detect/bit.rs b/library/stdarch/crates/std_detect/src/detect/bit.rs
new file mode 100644
index 00000000000..578f0b16b74
--- /dev/null
+++ b/library/stdarch/crates/std_detect/src/detect/bit.rs
@@ -0,0 +1,9 @@
+//! Bit manipulation utilities.
+
+/// Tests the `bit` of `x`.
+#[allow(dead_code)]
+#[inline]
+pub(crate) fn test(x: usize, bit: u32) -> bool {
+    debug_assert!(bit < 32, "bit index out-of-bounds");
+    x & (1 << bit) != 0
+}