99 lines
3.3 KiB
Zig
99 lines
3.3 KiB
Zig
// SPDX-License-Identifier: MIT
|
|
// Copyright (c) 2015-2020 Zig Contributors
|
|
// This file is part of [zig](https://ziglang.org/), which is MIT licensed.
|
|
// The MIT license requires this copyright notice to be included in all copies
|
|
// and substantial portions of the software.
|
|
const builtin = @import("builtin");
|
|
const std = @import("std");
|
|
const maxInt = std.math.maxInt;
|
|
|
|
const FLT_MANT_DIG = 24;
|
|
|
|
fn __floatXisf(comptime T: type, arg: T) f32 {
|
|
@setRuntimeSafety(builtin.is_test);
|
|
|
|
const bits = @typeInfo(T).Int.bits;
|
|
const Z = std.meta.Int(.unsigned, bits);
|
|
const S = std.meta.Int(.unsigned, bits - @clz(Z, @as(Z, bits) - 1));
|
|
|
|
if (arg == 0) {
|
|
return @as(f32, 0.0);
|
|
}
|
|
|
|
var ai = arg;
|
|
const N: u32 = bits;
|
|
const si = ai >> @intCast(S, (N - 1));
|
|
ai = ((ai ^ si) -% si);
|
|
var a = @bitCast(Z, ai);
|
|
|
|
const sd = @bitCast(i32, N - @clz(Z, a)); // number of significant digits
|
|
var e: i32 = sd - 1; // exponent
|
|
|
|
if (sd > FLT_MANT_DIG) {
|
|
// start: 0000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQxxxxxxxxxxxxxxxxxx
|
|
// finish: 000000000000000000000000000000000000001xxxxxxxxxxxxxxxxxxxxxxPQR
|
|
// 12345678901234567890123456
|
|
// 1 = msb 1 bit
|
|
// P = bit FLT_MANT_DIG-1 bits to the right of 1
|
|
// Q = bit FLT_MANT_DIG bits to the right of 1
|
|
// R = "or" of all bits to the right of Q
|
|
switch (sd) {
|
|
FLT_MANT_DIG + 1 => {
|
|
a <<= 1;
|
|
},
|
|
FLT_MANT_DIG + 2 => {},
|
|
else => {
|
|
const shift1_amt = @intCast(i32, sd - (FLT_MANT_DIG + 2));
|
|
const shift1_amt_u7 = @intCast(S, shift1_amt);
|
|
|
|
const shift2_amt = @intCast(i32, N + (FLT_MANT_DIG + 2)) - sd;
|
|
const shift2_amt_u7 = @intCast(S, shift2_amt);
|
|
|
|
a = (a >> shift1_amt_u7) | @boolToInt((a & (@intCast(Z, maxInt(Z)) >> shift2_amt_u7)) != 0);
|
|
},
|
|
}
|
|
// finish
|
|
a |= @boolToInt((a & 4) != 0); // Or P into R
|
|
a += 1; // round - this step may add a significant bit
|
|
a >>= 2; // dump Q and R
|
|
// a is now rounded to FLT_MANT_DIG or FLT_MANT_DIG+1 bits
|
|
if ((a & (@as(Z, 1) << FLT_MANT_DIG)) != 0) {
|
|
a >>= 1;
|
|
e += 1;
|
|
}
|
|
// a is now rounded to FLT_MANT_DIG bits
|
|
} else {
|
|
a <<= @intCast(S, FLT_MANT_DIG - sd);
|
|
// a is now rounded to FLT_MANT_DIG bits
|
|
}
|
|
|
|
const s = @bitCast(Z, arg) >> (@typeInfo(T).Int.bits - 32);
|
|
const r = (@intCast(u32, s) & 0x80000000) | // sign
|
|
(@intCast(u32, (e + 127)) << 23) | // exponent
|
|
(@truncate(u32, a) & 0x007fffff); // mantissa-high
|
|
|
|
return @bitCast(f32, r);
|
|
}
|
|
|
|
pub fn __floatdisf(arg: i64) callconv(.C) f32 {
|
|
@setRuntimeSafety(builtin.is_test);
|
|
return @call(.{ .modifier = .always_inline }, __floatXisf, .{ i64, arg });
|
|
}
|
|
|
|
pub fn __floattisf(arg: i128) callconv(.C) f32 {
|
|
@setRuntimeSafety(builtin.is_test);
|
|
return @call(.{ .modifier = .always_inline }, __floatXisf, .{ i128, arg });
|
|
}
|
|
|
|
pub fn __aeabi_l2f(arg: i64) callconv(.AAPCS) f32 {
|
|
@setRuntimeSafety(false);
|
|
return @call(.{ .modifier = .always_inline }, __floatdisf, .{arg});
|
|
}
|
|
|
|
test "import floattisf" {
|
|
_ = @import("floattisf_test.zig");
|
|
}
|
|
test "import floatdisf" {
|
|
_ = @import("floattisf_test.zig");
|
|
}
|