diff options
Diffstat (limited to 'vendor/half/src/bfloat')
-rw-r--r-- | vendor/half/src/bfloat/convert.rs | 148 |
1 files changed, 0 insertions, 148 deletions
diff --git a/vendor/half/src/bfloat/convert.rs b/vendor/half/src/bfloat/convert.rs deleted file mode 100644 index 8f258f5..0000000 --- a/vendor/half/src/bfloat/convert.rs +++ /dev/null @@ -1,148 +0,0 @@ -use crate::leading_zeros::leading_zeros_u16; -use core::mem; - -#[inline] -pub(crate) const fn f32_to_bf16(value: f32) -> u16 { - // TODO: Replace mem::transmute with to_bits() once to_bits is const-stabilized - // Convert to raw bytes - let x: u32 = unsafe { mem::transmute(value) }; - - // check for NaN - if x & 0x7FFF_FFFFu32 > 0x7F80_0000u32 { - // Keep high part of current mantissa but also set most significiant mantissa bit - return ((x >> 16) | 0x0040u32) as u16; - } - - // round and shift - let round_bit = 0x0000_8000u32; - if (x & round_bit) != 0 && (x & (3 * round_bit - 1)) != 0 { - (x >> 16) as u16 + 1 - } else { - (x >> 16) as u16 - } -} - -#[inline] -pub(crate) const fn f64_to_bf16(value: f64) -> u16 { - // TODO: Replace mem::transmute with to_bits() once to_bits is const-stabilized - // Convert to raw bytes, truncating the last 32-bits of mantissa; that precision will always - // be lost on half-precision. - let val: u64 = unsafe { mem::transmute(value) }; - let x = (val >> 32) as u32; - - // Extract IEEE754 components - let sign = x & 0x8000_0000u32; - let exp = x & 0x7FF0_0000u32; - let man = x & 0x000F_FFFFu32; - - // Check for all exponent bits being set, which is Infinity or NaN - if exp == 0x7FF0_0000u32 { - // Set mantissa MSB for NaN (and also keep shifted mantissa bits). - // We also have to check the last 32 bits. - let nan_bit = if man == 0 && (val as u32 == 0) { - 0 - } else { - 0x0040u32 - }; - return ((sign >> 16) | 0x7F80u32 | nan_bit | (man >> 13)) as u16; - } - - // The number is normalized, start assembling half precision version - let half_sign = sign >> 16; - // Unbias the exponent, then bias for bfloat16 precision - let unbiased_exp = ((exp >> 20) as i64) - 1023; - let half_exp = unbiased_exp + 127; - - // Check for exponent overflow, return +infinity - if half_exp >= 0xFF { - return (half_sign | 0x7F80u32) as u16; - } - - // Check for underflow - if half_exp <= 0 { - // Check mantissa for what we can do - if 7 - half_exp > 21 { - // No rounding possibility, so this is a full underflow, return signed zero - return half_sign as u16; - } - // Don't forget about hidden leading mantissa bit when assembling mantissa - let man = man | 0x0010_0000u32; - let mut half_man = man >> (14 - half_exp); - // Check for rounding - let round_bit = 1 << (13 - half_exp); - if (man & round_bit) != 0 && (man & (3 * round_bit - 1)) != 0 { - half_man += 1; - } - // No exponent for subnormals - return (half_sign | half_man) as u16; - } - - // Rebias the exponent - let half_exp = (half_exp as u32) << 7; - let half_man = man >> 13; - // Check for rounding - let round_bit = 0x0000_1000u32; - if (man & round_bit) != 0 && (man & (3 * round_bit - 1)) != 0 { - // Round it - ((half_sign | half_exp | half_man) + 1) as u16 - } else { - (half_sign | half_exp | half_man) as u16 - } -} - -#[inline] -pub(crate) const fn bf16_to_f32(i: u16) -> f32 { - // TODO: Replace mem::transmute with from_bits() once from_bits is const-stabilized - // If NaN, keep current mantissa but also set most significiant mantissa bit - if i & 0x7FFFu16 > 0x7F80u16 { - unsafe { mem::transmute((i as u32 | 0x0040u32) << 16) } - } else { - unsafe { mem::transmute((i as u32) << 16) } - } -} - -#[inline] -pub(crate) const fn bf16_to_f64(i: u16) -> f64 { - // TODO: Replace mem::transmute with from_bits() once from_bits is const-stabilized - // Check for signed zero - if i & 0x7FFFu16 == 0 { - return unsafe { mem::transmute((i as u64) << 48) }; - } - - let half_sign = (i & 0x8000u16) as u64; - let half_exp = (i & 0x7F80u16) as u64; - let half_man = (i & 0x007Fu16) as u64; - - // Check for an infinity or NaN when all exponent bits set - if half_exp == 0x7F80u64 { - // Check for signed infinity if mantissa is zero - if half_man == 0 { - return unsafe { mem::transmute((half_sign << 48) | 0x7FF0_0000_0000_0000u64) }; - } else { - // NaN, keep current mantissa but also set most significiant mantissa bit - return unsafe { - mem::transmute((half_sign << 48) | 0x7FF8_0000_0000_0000u64 | (half_man << 45)) - }; - } - } - - // Calculate double-precision components with adjusted exponent - let sign = half_sign << 48; - // Unbias exponent - let unbiased_exp = ((half_exp as i64) >> 7) - 127; - - // Check for subnormals, which will be normalized by adjusting exponent - if half_exp == 0 { - // Calculate how much to adjust the exponent by - let e = leading_zeros_u16(half_man as u16) - 9; - - // Rebias and adjust exponent - let exp = ((1023 - 127 - e) as u64) << 52; - let man = (half_man << (46 + e)) & 0xF_FFFF_FFFF_FFFFu64; - return unsafe { mem::transmute(sign | exp | man) }; - } - // Rebias exponent for a normalized normal - let exp = ((unbiased_exp + 1023) as u64) << 52; - let man = (half_man & 0x007Fu64) << 45; - unsafe { mem::transmute(sign | exp | man) } -} |