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41dd2beaac
* unify the logic for exporting math functions from compiler-rt,
with the appropriate suffixes and prefixes.
- add all missing f128 and f80 exports. Functions with missing
implementations call other functions and have TODO comments.
- also add f16 functions
* move math functions from freestanding libc to compiler-rt (#7265)
* enable all the f128 and f80 code in the stage2 compiler and behavior
tests (#11161).
* update std lib to use builtins rather than `std.math`.
40 lines
1.1 KiB
Zig
40 lines
1.1 KiB
Zig
const std = @import("../std.zig");
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const math = std.math;
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const expect = std.testing.expect;
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/// Returns the base-2 logarithm of x.
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///
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/// Special Cases:
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/// - log2(+inf) = +inf
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/// - log2(0) = -inf
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/// - log2(x) = nan if x < 0
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/// - log2(nan) = nan
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pub fn log2(x: anytype) @TypeOf(x) {
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const T = @TypeOf(x);
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switch (@typeInfo(T)) {
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.ComptimeFloat => {
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return @as(comptime_float, @log2(x));
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},
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.Float => return @log2(x),
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.ComptimeInt => comptime {
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var result = 0;
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var x_shifted = x;
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while (b: {
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x_shifted >>= 1;
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break :b x_shifted != 0;
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}) : (result += 1) {}
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return result;
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},
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.Int => |IntType| switch (IntType.signedness) {
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.signed => @compileError("log2 not implemented for signed integers"),
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.unsigned => return math.log2_int(T, x),
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},
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else => @compileError("log2 not implemented for " ++ @typeName(T)),
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}
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}
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test "log2" {
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try expect(log2(@as(f32, 0.2)) == @log2(0.2));
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try expect(log2(@as(f64, 0.2)) == @log2(0.2));
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}
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