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add helper macro for const generics gather instructions' scales

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Rémy Rakic 2021-03-06 00:34:58 +01:00 • committed by Amanieu d'Antras
parent 216a257212
commit d4558e1b30
1 changed files with 16 additions and 0 deletions
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16
library/stdarch/crates/core_arch/src/x86/macros.rs
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@ -49,6 +49,22 @@ macro_rules! static_assert_imm_u8 {
};
}
// Helper struct used to trigger const eval errors when the const generic immediate value `SCALE` is
// not valid for gather instructions: the only valid scale values are 1, 2, 4 and 8.
pub(crate) struct ValidateConstGatherScale<const SCALE: i32>;
impl<const SCALE: i32> ValidateConstGatherScale<SCALE> {
pub(crate) const VALID: () = {
let _ = 1 / ((SCALE == 1 || SCALE == 2 || SCALE == 4 || SCALE == 8) as usize);
};
}
#[allow(unused)]
macro_rules! static_assert_imm8_scale {
($imm:ident) => {
let _ = $crate::core_arch::x86::macros::ValidateConstGatherScale::<$imm>::VALID;
};
}
macro_rules! constify_imm3 {
($imm8:expr, $expand:ident) => {
#[allow(overflowing_literals)]