39 lines
1.1 KiB
Zig
39 lines
1.1 KiB
Zig
const builtin = @import("builtin");
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const is_test = builtin.is_test;
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const std = @import("std");
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const maxInt = std.math.maxInt;
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const significandBits = 112;
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const exponentBias = 16383;
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const implicitBit = (@as(u128, 1) << significandBits);
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pub fn __floatditf(arg: i64) callconv(.C) f128 {
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@setRuntimeSafety(is_test);
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if (arg == 0)
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return 0.0;
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// All other cases begin by extracting the sign and absolute value of a
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var sign: u128 = 0;
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var aAbs = @bitCast(u64, arg);
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if (arg < 0) {
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sign = 1 << 127;
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aAbs = ~@bitCast(u64, arg) + 1;
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}
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// Exponent of (fp_t)a is the width of abs(a).
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const exponent = 63 - @clz(u64, aAbs);
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var result: u128 = undefined;
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// Shift a into the significand field, rounding if it is a right-shift
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const shift = significandBits - exponent;
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result = @as(u128, aAbs) << shift ^ implicitBit;
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result += (@as(u128, exponent) + exponentBias) << significandBits;
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return @bitCast(f128, result | sign);
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}
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test "import floatditf" {
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_ = @import("floatditf_test.zig");
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}
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