zig/std/math/trunc.zig
Andrew Kelley b8ed0cb374 remove workaround for LLVM not respecting "nobuiltin"
now that we depend on LLVM 5.0.0 we can remove the
workaround.

closes #393
2017-08-28 04:28:42 -04:00

93 lines
2.0 KiB
Zig

// Special Cases:
//
// - trunc(+-0) = +-0
// - trunc(+-inf) = +-inf
// - trunc(nan) = nan
const math = @import("index.zig");
const assert = @import("../debug.zig").assert;
pub fn trunc(x: var) -> @typeOf(x) {
const T = @typeOf(x);
switch (T) {
f32 => @inlineCall(trunc32, x),
f64 => @inlineCall(trunc64, x),
else => @compileError("trunc not implemented for " ++ @typeName(T)),
}
}
fn trunc32(x: f32) -> f32 {
const u = @bitCast(u32, x);
var e = i32(((u >> 23) & 0xFF)) - 0x7F + 9;
var m: u32 = undefined;
if (e >= 23 + 9) {
return x;
}
if (e < 9) {
e = 1;
}
m = u32(@maxValue(u32)) >> u5(e);
if (u & m == 0) {
x
} else {
math.forceEval(x + 0x1p120);
@bitCast(f32, u & ~m)
}
}
fn trunc64(x: f64) -> f64 {
const u = @bitCast(u64, x);
var e = i32(((u >> 52) & 0x7FF)) - 0x3FF + 12;
var m: u64 = undefined;
if (e >= 52 + 12) {
return x;
}
if (e < 12) {
e = 1;
}
m = u64(@maxValue(u64)) >> u6(e);
if (u & m == 0) {
x
} else {
math.forceEval(x + 0x1p120);
@bitCast(f64, u & ~m)
}
}
test "math.trunc" {
assert(trunc(f32(1.3)) == trunc32(1.3));
assert(trunc(f64(1.3)) == trunc64(1.3));
}
test "math.trunc32" {
assert(trunc32(1.3) == 1.0);
assert(trunc32(-1.3) == -1.0);
assert(trunc32(0.2) == 0.0);
}
test "math.trunc64" {
assert(trunc64(1.3) == 1.0);
assert(trunc64(-1.3) == -1.0);
assert(trunc64(0.2) == 0.0);
}
test "math.trunc32.special" {
assert(trunc32(0.0) == 0.0); // 0x3F800000
assert(trunc32(-0.0) == -0.0);
assert(math.isPositiveInf(trunc32(math.inf(f32))));
assert(math.isNegativeInf(trunc32(-math.inf(f32))));
assert(math.isNan(trunc32(math.nan(f32))));
}
test "math.trunc64.special" {
assert(trunc64(0.0) == 0.0);
assert(trunc64(-0.0) == -0.0);
assert(math.isPositiveInf(trunc64(math.inf(f64))));
assert(math.isNegativeInf(trunc64(-math.inf(f64))));
assert(math.isNan(trunc64(math.nan(f64))));
}