feature comments in Cargo.toml

1 files changed, 7 insertions, 0 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 756703c..fbdd9e7 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,7 +6,14 @@ edition = "2018"
 
 [features]
 default = ["std"]
+# Like SSE4.1 and AVX2, the AVX-512 implementation uses dynamic feature
+# detection, so a binary with "c_avx512" on is still cross-platform.
 c_avx512 = []
+# The NEON implementation does not use dynamic feature detection. If "c_neon"
+# is on, NEON support is assumed. Note that AArch64 always supports NEON, but
+# support on ARMv7 varies. (See also comments about ARMv7 in build.rs. You'll
+# probably need to uncomment some flags there to convince the C compiler to
+# turn on NEON support.)
 c_neon = []
 std = []