zig/lib/compiler_rt/trunc.zig
Andrew Kelley ec95e00e28 flatten lib/std/special and improve "pkg inside another" logic
stage2: change logic for detecting whether the main package is inside
the std package. Previously it relied on realpath() which is not portable.
This uses resolve() which is how imports already work.

 * stage2: fix cleanup bug when creating Module
 * flatten lib/std/special/* to lib/*
   - this was motivated by making main_pkg_is_inside_std false for
     compiler_rt & friends.
 * rename "mini libc" to "universal libc"
2022-05-06 22:41:00 -07:00

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// Ported from musl, which is licensed under the MIT license:
// https://git.musl-libc.org/cgit/musl/tree/COPYRIGHT
//
// https://git.musl-libc.org/cgit/musl/tree/src/math/truncf.c
// https://git.musl-libc.org/cgit/musl/tree/src/math/trunc.c
const std = @import("std");
const math = std.math;
const expect = std.testing.expect;
pub fn __trunch(x: f16) callconv(.C) f16 {
// TODO: more efficient implementation
return @floatCast(f16, truncf(x));
}
pub fn truncf(x: f32) callconv(.C) f32 {
const u = @bitCast(u32, x);
var e = @intCast(i32, ((u >> 23) & 0xFF)) - 0x7F + 9;
var m: u32 = undefined;
if (e >= 23 + 9) {
return x;
}
if (e < 9) {
e = 1;
}
m = @as(u32, math.maxInt(u32)) >> @intCast(u5, e);
if (u & m == 0) {
return x;
} else {
math.doNotOptimizeAway(x + 0x1p120);
return @bitCast(f32, u & ~m);
}
}
pub fn trunc(x: f64) callconv(.C) f64 {
const u = @bitCast(u64, x);
var e = @intCast(i32, ((u >> 52) & 0x7FF)) - 0x3FF + 12;
var m: u64 = undefined;
if (e >= 52 + 12) {
return x;
}
if (e < 12) {
e = 1;
}
m = @as(u64, math.maxInt(u64)) >> @intCast(u6, e);
if (u & m == 0) {
return x;
} else {
math.doNotOptimizeAway(x + 0x1p120);
return @bitCast(f64, u & ~m);
}
}
pub fn __truncx(x: f80) callconv(.C) f80 {
// TODO: more efficient implementation
return @floatCast(f80, truncq(x));
}
pub fn truncq(x: f128) callconv(.C) f128 {
const u = @bitCast(u128, x);
var e = @intCast(i32, ((u >> 112) & 0x7FFF)) - 0x3FFF + 16;
var m: u128 = undefined;
if (e >= 112 + 16) {
return x;
}
if (e < 16) {
e = 1;
}
m = @as(u128, math.maxInt(u128)) >> @intCast(u7, e);
if (u & m == 0) {
return x;
} else {
math.doNotOptimizeAway(x + 0x1p120);
return @bitCast(f128, u & ~m);
}
}
test "trunc32" {
try expect(truncf(1.3) == 1.0);
try expect(truncf(-1.3) == -1.0);
try expect(truncf(0.2) == 0.0);
}
test "trunc64" {
try expect(trunc(1.3) == 1.0);
try expect(trunc(-1.3) == -1.0);
try expect(trunc(0.2) == 0.0);
}
test "trunc128" {
try expect(truncq(1.3) == 1.0);
try expect(truncq(-1.3) == -1.0);
try expect(truncq(0.2) == 0.0);
}
test "trunc32.special" {
try expect(truncf(0.0) == 0.0); // 0x3F800000
try expect(truncf(-0.0) == -0.0);
try expect(math.isPositiveInf(truncf(math.inf(f32))));
try expect(math.isNegativeInf(truncf(-math.inf(f32))));
try expect(math.isNan(truncf(math.nan(f32))));
}
test "trunc64.special" {
try expect(trunc(0.0) == 0.0);
try expect(trunc(-0.0) == -0.0);
try expect(math.isPositiveInf(trunc(math.inf(f64))));
try expect(math.isNegativeInf(trunc(-math.inf(f64))));
try expect(math.isNan(trunc(math.nan(f64))));
}
test "trunc128.special" {
try expect(truncq(0.0) == 0.0);
try expect(truncq(-0.0) == -0.0);
try expect(math.isPositiveInf(truncq(math.inf(f128))));
try expect(math.isNegativeInf(truncq(-math.inf(f128))));
try expect(math.isNan(truncq(math.nan(f128))));
}