extras: 1. call update_simd_len() after inferring bit_len for arguments
of certain intrinsics
2. handle the effective bit_len for _mm_mpsadbw_epu8 intrinsic's `imm8`
argument which has only 3 bits that are used
array.
Extra: 1. Added better load fuctions 2. Added an update_simd_len()
function to support cases where the bit_len of the element need to be
inferred from its partner arguments before calculating the simd_len
certain cases (like uint32_t to uint64_t)
extras: 1. added more C++ headers 2. typecasting integer constants (for
example, the MM_FROUND arguments) for type compatibility
This instruction is only available when the jsconv target_feature is available,
so on ARMv8.3 or higher.
It is used e.g. by Ruffle[0] to speed up its conversion from f64 to i32, or by
any JS engine probably.
I’ve picked the stdarch_aarch64_jscvt feature because it’s the name of the
FEAT_JSCVT, but hesitated with naming it stdarch_aarch64_jsconv (the name of
the target_feature) or stdarch_aarch64_jcvt (the name of the C intrinsic) or
stdarch_aarch64_fjcvtzs (the name of the instruction), this choice is purely
arbitrary and I guess it could be argued one way or another. I wouldn’t expect
it to stay unstable for too long, so ultimately this shouldn’t matter much.
This feature is now tracked in this issue[1].
[0] https://github.com/ruffle-rs/ruffle/pull/21780
[1] https://github.com/rust-lang/rust/issues/147555
They are defined in the aarch64 module, so this cfg is pointless.
Note that these instructions do exist for arm, but the aarch64 ones are
already stable, so this would need some additional work to implement
them for arm.
While many intrinsics use `.insn` to generate raw machine code from
numbers, all ratified instructions can be symbolic
using `.option` directives.
By saving the assembler environment with `.option push` then modifying
the architecture with `.option arch`, we can temporarily enable certain
extensions (as we use `.option pop` immediately after the target
instruction, surrounding environment is completely intact in this
commit; *almost* completely intact in general).
This commit modifies the `pause` *hint* intrinsic to use symbolic
*instruction* because we want to expose it even if the Zihintpause
extension is unavailable on the target.
