forked from AbleOS/holey-bytes
67 lines
1.9 KiB
Rust
67 lines
1.9 KiB
Rust
use {core::arch::asm, hbbytecode::RoundingMode};
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macro_rules! fnsdef {
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{$(
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$(#[$attr:meta])*
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$vis:vis fn $name:ident[$inreg:ident -> $outreg:ident]($from:ident -> $to:ident): $ins:literal;
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)*} => {$(
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$(#[$attr])*
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$vis fn $name(val: $from, mode: RoundingMode) -> $to {
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let result: $to;
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unsafe {
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set_rounding_mode(mode);
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asm!(
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$ins,
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out($outreg) result,
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in($inreg) val,
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);
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default_rounding_mode();
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}
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result
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}
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)*};
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}
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fnsdef! {
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/// Convert [`f64`] to [`f32`] with chosen rounding mode
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pub fn conv64to32[vreg -> vreg](f64 -> f32): "fcvt {:s}, {:d}";
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/// Convert [`f32`] to [`i64`] with chosen rounding mode
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pub fn f32toint[vreg -> reg](f32 -> i64): "fcvtzs {}, {:s}";
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/// Convert [`f64`] to [`i64`] with chosen rounding mode
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pub fn f64toint[vreg -> reg](f64 -> i64): "fcvtzs {}, {:d}";
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}
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/// Set rounding mode
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///
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/// # Safety
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/// - Do not call if rounding mode isn't [`RoundingMode::NearestEven`]
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/// - Do not perform any Rust FP operations until reset using
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/// [`default_rounding_mode`], you have to rely on inline assembly
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#[inline(always)]
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unsafe fn set_rounding_mode(mode: RoundingMode) {
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if mode == RoundingMode::NearestEven {
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return;
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}
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let fpcr: u64;
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asm!("mrs {}, fpcr", out(reg) fpcr);
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let fpcr = fpcr & !(0b11 << 22)
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RoundingMode::NearestEven => 0b00,
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RoundingMode::Truncate => 0b11,
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RoundingMode::Up => 0b01,
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RoundingMode::Down => 0b10,
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}) << 22;
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asm!("msr fpcr, {}", in(reg) fpcr);
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}
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#[inline(always)]
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unsafe fn default_rounding_mode() {
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// I hope so much it gets optimised
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set_rounding_mode(RoundingMode::NearestEven);
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}
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