`asm` macro does not understand that enabling the target feature `avx2` implies `avx`

[shepmaster]

I tried this code:

#[target_feature(enable = "avx2")]
unsafe fn demo(v: std::arch::x86_64::__m256i) {
    std::arch::asm!("/* {v} */", v = in(ymm_reg) v);
}

According to the Rust Reference, the avx2 feature should imply the avx feature (and further features), so I expected the code to compile.

Instead, this happened:

error: register class `ymm_reg` requires the `avx` target feature
 --> src/lib.rs:3:34
  |
3 |     std::arch::asm!("/* {v} */", v = in(ymm_reg) v);
  |                                  ^^^^^^^^^^^^^^^^^

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