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Erin 2024-01-15 17:51:08 +01:00
parent 8374dfe20a
commit a84e93d562
1 changed files with 17 additions and 26 deletions
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43
hbvm/src/float/x86_64.rs
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@ -30,9 +30,24 @@ macro_rules! fnsdef {
$vis fn $name(val: $from, mode: RoundingMode) -> $to {
let result: $to;
unsafe {
set_rounding_mode(mode);
let mut mxcsr = 0_u32;
'a: {
asm!("stmxcsr {}", in(reg) &mut mxcsr);
asm!(
"ldmxcsr {}",
in(reg) &(mxcsr & !arin::_MM_ROUND_MASK | match mode {
RoundingMode::NearestEven => break 'a,
RoundingMode::Truncate => arin::_MM_ROUND_TOWARD_ZERO,
RoundingMode::Up => arin::_MM_ROUND_UP,
RoundingMode::Down => arin::_MM_ROUND_DOWN,
})
);
}
op!($ins, val, result => $to);
default_rounding_mode();
// Set MXCSR to original value
asm!("ldmxcsr {}", in(reg) &mxcsr);
}
result
}
@ -47,27 +62,3 @@ fnsdef! {
/// Convert [`f64`] to [`i64`] with chosen rounding mode
pub fn f64toint(f64 -> i64): "cvttsd2si";
}
/// Set rounding mode
///
/// # Safety
/// - Do not call if rounding mode isn't [`RoundingMode::NearestEven`]
/// - Do not perform any Rust FP operations until reset using
/// [`default_rounding_mode`], you have to rely on inline assembly
#[inline(always)]
unsafe fn set_rounding_mode(mode: RoundingMode) {
unsafe {
arin::_MM_SET_ROUNDING_MODE(match mode {
RoundingMode::NearestEven => return,
RoundingMode::Truncate => arin::_MM_ROUND_TOWARD_ZERO,
RoundingMode::Up => arin::_MM_ROUND_UP,
RoundingMode::Down => arin::_MM_ROUND_DOWN,
})
}
}
#[inline(always)]
fn default_rounding_mode() {
// SAFETY: This is said to be the default mode, do not trust me.
unsafe { arin::_MM_SET_ROUNDING_MODE(arin::_MM_ROUND_NEAREST) };
}