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1265 lines (1111 loc) · 36 KB
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//! This is Zig's multi-target implementation of libc.
//! When builtin.link_libc is true, we need to export all the functions and
//! provide an entire C API.
//! Otherwise, only the functions which LLVM generates calls to need to be generated,
//! such as memcpy, memset, and some math functions.
const std = @import("std");
const builtin = @import("builtin");
const math = std.math;
const isNan = std.math.isNan;
const maxInt = std.math.maxInt;
const native_os = builtin.os.tag;
const native_arch = builtin.cpu.arch;
const native_abi = builtin.abi;
const long_double_is_f128 = builtin.target.longDoubleIs(f128);
const is_wasm = switch (native_arch) {
.wasm32, .wasm64 => true,
else => false,
};
const is_msvc = switch (native_abi) {
.msvc => true,
else => false,
};
const is_freestanding = switch (native_os) {
.freestanding => true,
else => false,
};
comptime {
if (is_freestanding and is_wasm and builtin.link_libc) {
@export(wasm_start, .{ .name = "_start", .linkage = .Strong });
}
if (native_os == .linux) {
@export(clone, .{ .name = "clone" });
}
@export(memset, .{ .name = "memset", .linkage = .Strong });
@export(__memset, .{ .name = "__memset", .linkage = .Strong });
@export(memcpy, .{ .name = "memcpy", .linkage = .Strong });
@export(memmove, .{ .name = "memmove", .linkage = .Strong });
@export(memcmp, .{ .name = "memcmp", .linkage = .Strong });
@export(bcmp, .{ .name = "bcmp", .linkage = .Strong });
if (builtin.link_libc) {
@export(strcmp, .{ .name = "strcmp", .linkage = .Strong });
@export(strncmp, .{ .name = "strncmp", .linkage = .Strong });
@export(strerror, .{ .name = "strerror", .linkage = .Strong });
@export(strlen, .{ .name = "strlen", .linkage = .Strong });
@export(strcpy, .{ .name = "strcpy", .linkage = .Strong });
@export(strncpy, .{ .name = "strncpy", .linkage = .Strong });
@export(strcat, .{ .name = "strcat", .linkage = .Strong });
@export(strncat, .{ .name = "strncat", .linkage = .Strong });
} else if (is_msvc) {
@export(_fltused, .{ .name = "_fltused", .linkage = .Strong });
}
@export(trunc, .{ .name = "trunc", .linkage = .Strong });
@export(truncf, .{ .name = "truncf", .linkage = .Strong });
@export(truncl, .{ .name = "truncl", .linkage = .Strong });
@export(log, .{ .name = "log", .linkage = .Strong });
@export(logf, .{ .name = "logf", .linkage = .Strong });
@export(sin, .{ .name = "sin", .linkage = .Strong });
@export(sinf, .{ .name = "sinf", .linkage = .Strong });
@export(cos, .{ .name = "cos", .linkage = .Strong });
@export(cosf, .{ .name = "cosf", .linkage = .Strong });
@export(exp, .{ .name = "exp", .linkage = .Strong });
@export(expf, .{ .name = "expf", .linkage = .Strong });
@export(exp2, .{ .name = "exp2", .linkage = .Strong });
@export(exp2f, .{ .name = "exp2f", .linkage = .Strong });
@export(log2, .{ .name = "log2", .linkage = .Strong });
@export(log2f, .{ .name = "log2f", .linkage = .Strong });
@export(log10, .{ .name = "log10", .linkage = .Strong });
@export(log10f, .{ .name = "log10f", .linkage = .Strong });
@export(fmod, .{ .name = "fmod", .linkage = .Strong });
@export(fmodf, .{ .name = "fmodf", .linkage = .Strong });
@export(sincos, .{ .name = "sincos", .linkage = .Strong });
@export(sincosf, .{ .name = "sincosf", .linkage = .Strong });
@export(fabs, .{ .name = "fabs", .linkage = .Strong });
@export(fabsf, .{ .name = "fabsf", .linkage = .Strong });
@export(round, .{ .name = "round", .linkage = .Strong });
@export(roundf, .{ .name = "roundf", .linkage = .Strong });
@export(roundl, .{ .name = "roundl", .linkage = .Strong });
@export(fmin, .{ .name = "fmin", .linkage = .Strong });
@export(fminf, .{ .name = "fminf", .linkage = .Strong });
@export(fmax, .{ .name = "fmax", .linkage = .Strong });
@export(fmaxf, .{ .name = "fmaxf", .linkage = .Strong });
@export(sqrt, .{ .name = "sqrt", .linkage = .Strong });
@export(sqrtf, .{ .name = "sqrtf", .linkage = .Strong });
}
// Avoid dragging in the runtime safety mechanisms into this .o file,
// unless we're trying to test this file.
pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace) noreturn {
@setCold(true);
_ = error_return_trace;
if (builtin.is_test) {
std.debug.panic("{s}", .{msg});
}
if (native_os != .freestanding and native_os != .other) {
std.os.abort();
}
while (true) {}
}
extern fn main(argc: c_int, argv: [*:null]?[*:0]u8) c_int;
fn wasm_start() callconv(.C) void {
_ = main(0, undefined);
}
fn memset(dest: ?[*]u8, c: u8, len: usize) callconv(.C) ?[*]u8 {
@setRuntimeSafety(false);
if (len != 0) {
var d = dest.?;
var n = len;
while (true) {
d.* = c;
n -= 1;
if (n == 0) break;
d += 1;
}
}
return dest;
}
fn __memset(dest: ?[*]u8, c: u8, n: usize, dest_n: usize) callconv(.C) ?[*]u8 {
if (dest_n < n)
@panic("buffer overflow");
return memset(dest, c, n);
}
fn memcpy(noalias dest: ?[*]u8, noalias src: ?[*]const u8, len: usize) callconv(.C) ?[*]u8 {
@setRuntimeSafety(false);
if (len != 0) {
var d = dest.?;
var s = src.?;
var n = len;
while (true) {
d[0] = s[0];
n -= 1;
if (n == 0) break;
d += 1;
s += 1;
}
}
return dest;
}
fn memmove(dest: ?[*]u8, src: ?[*]const u8, n: usize) callconv(.C) ?[*]u8 {
@setRuntimeSafety(false);
if (@ptrToInt(dest) < @ptrToInt(src)) {
var index: usize = 0;
while (index != n) : (index += 1) {
dest.?[index] = src.?[index];
}
} else {
var index = n;
while (index != 0) {
index -= 1;
dest.?[index] = src.?[index];
}
}
return dest;
}
fn memcmp(vl: ?[*]const u8, vr: ?[*]const u8, n: usize) callconv(.C) c_int {
@setRuntimeSafety(false);
var index: usize = 0;
while (index != n) : (index += 1) {
const compare_val = @bitCast(i8, vl.?[index] -% vr.?[index]);
if (compare_val != 0) {
return compare_val;
}
}
return 0;
}
test "memcmp" {
const base_arr = &[_]u8{ 1, 1, 1 };
const arr1 = &[_]u8{ 1, 1, 1 };
const arr2 = &[_]u8{ 1, 0, 1 };
const arr3 = &[_]u8{ 1, 2, 1 };
try std.testing.expect(memcmp(base_arr[0..], arr1[0..], base_arr.len) == 0);
try std.testing.expect(memcmp(base_arr[0..], arr2[0..], base_arr.len) > 0);
try std.testing.expect(memcmp(base_arr[0..], arr3[0..], base_arr.len) < 0);
}
fn bcmp(vl: [*]allowzero const u8, vr: [*]allowzero const u8, n: usize) callconv(.C) c_int {
@setRuntimeSafety(false);
var index: usize = 0;
while (index != n) : (index += 1) {
if (vl[index] != vr[index]) {
return 1;
}
}
return 0;
}
test "bcmp" {
const base_arr = &[_]u8{ 1, 1, 1 };
const arr1 = &[_]u8{ 1, 1, 1 };
const arr2 = &[_]u8{ 1, 0, 1 };
const arr3 = &[_]u8{ 1, 2, 1 };
try std.testing.expect(bcmp(base_arr[0..], arr1[0..], base_arr.len) == 0);
try std.testing.expect(bcmp(base_arr[0..], arr2[0..], base_arr.len) != 0);
try std.testing.expect(bcmp(base_arr[0..], arr3[0..], base_arr.len) != 0);
}
var _fltused: c_int = 1;
fn strcpy(dest: [*:0]u8, src: [*:0]const u8) callconv(.C) [*:0]u8 {
var i: usize = 0;
while (src[i] != 0) : (i += 1) {
dest[i] = src[i];
}
dest[i] = 0;
return dest;
}
test "strcpy" {
var s1: [9:0]u8 = undefined;
s1[0] = 0;
_ = strcpy(&s1, "foobarbaz");
try std.testing.expectEqualSlices(u8, "foobarbaz", std.mem.sliceTo(&s1, 0));
}
fn strncpy(dest: [*:0]u8, src: [*:0]const u8, n: usize) callconv(.C) [*:0]u8 {
var i: usize = 0;
while (i < n and src[i] != 0) : (i += 1) {
dest[i] = src[i];
}
while (i < n) : (i += 1) {
dest[i] = 0;
}
return dest;
}
test "strncpy" {
var s1: [9:0]u8 = undefined;
s1[0] = 0;
_ = strncpy(&s1, "foobarbaz", @sizeOf(@TypeOf(s1)));
try std.testing.expectEqualSlices(u8, "foobarbaz", std.mem.sliceTo(&s1, 0));
}
fn strcat(dest: [*:0]u8, src: [*:0]const u8) callconv(.C) [*:0]u8 {
var dest_end: usize = 0;
while (dest[dest_end] != 0) : (dest_end += 1) {}
var i: usize = 0;
while (src[i] != 0) : (i += 1) {
dest[dest_end + i] = src[i];
}
dest[dest_end + i] = 0;
return dest;
}
test "strcat" {
var s1: [9:0]u8 = undefined;
s1[0] = 0;
_ = strcat(&s1, "foo");
_ = strcat(&s1, "bar");
_ = strcat(&s1, "baz");
try std.testing.expectEqualSlices(u8, "foobarbaz", std.mem.sliceTo(&s1, 0));
}
fn strncat(dest: [*:0]u8, src: [*:0]const u8, avail: usize) callconv(.C) [*:0]u8 {
var dest_end: usize = 0;
while (dest[dest_end] != 0) : (dest_end += 1) {}
var i: usize = 0;
while (i < avail and src[i] != 0) : (i += 1) {
dest[dest_end + i] = src[i];
}
dest[dest_end + i] = 0;
return dest;
}
test "strncat" {
var s1: [9:0]u8 = undefined;
s1[0] = 0;
_ = strncat(&s1, "foo1111", 3);
_ = strncat(&s1, "bar1111", 3);
_ = strncat(&s1, "baz1111", 3);
try std.testing.expectEqualSlices(u8, "foobarbaz", std.mem.sliceTo(&s1, 0));
}
fn strcmp(s1: [*:0]const u8, s2: [*:0]const u8) callconv(.C) c_int {
return std.cstr.cmp(s1, s2);
}
fn strlen(s: [*:0]const u8) callconv(.C) usize {
return std.mem.len(s);
}
fn strncmp(_l: [*:0]const u8, _r: [*:0]const u8, _n: usize) callconv(.C) c_int {
if (_n == 0) return 0;
var l = _l;
var r = _r;
var n = _n - 1;
while (l[0] != 0 and r[0] != 0 and n != 0 and l[0] == r[0]) {
l += 1;
r += 1;
n -= 1;
}
return @as(c_int, l[0]) - @as(c_int, r[0]);
}
fn strerror(errnum: c_int) callconv(.C) [*:0]const u8 {
_ = errnum;
return "TODO strerror implementation";
}
test "strncmp" {
try std.testing.expect(strncmp("a", "b", 1) == -1);
try std.testing.expect(strncmp("a", "c", 1) == -2);
try std.testing.expect(strncmp("b", "a", 1) == 1);
try std.testing.expect(strncmp("\xff", "\x02", 1) == 253);
}
fn trunc(a: f64) callconv(.C) f64 {
return math.trunc(a);
}
fn truncf(a: f32) callconv(.C) f32 {
return math.trunc(a);
}
fn truncl(a: c_longdouble) callconv(.C) c_longdouble {
if (!long_double_is_f128) {
@panic("TODO implement this");
}
return math.trunc(a);
}
fn log(a: f64) callconv(.C) f64 {
return math.ln(a);
}
fn logf(a: f32) callconv(.C) f32 {
return math.ln(a);
}
fn sin(a: f64) callconv(.C) f64 {
return math.sin(a);
}
fn sinf(a: f32) callconv(.C) f32 {
return math.sin(a);
}
fn cos(a: f64) callconv(.C) f64 {
return math.cos(a);
}
fn cosf(a: f32) callconv(.C) f32 {
return math.cos(a);
}
fn exp(a: f64) callconv(.C) f64 {
return math.exp(a);
}
fn expf(a: f32) callconv(.C) f32 {
return math.exp(a);
}
fn exp2(a: f64) callconv(.C) f64 {
return math.exp2(a);
}
fn exp2f(a: f32) callconv(.C) f32 {
return math.exp2(a);
}
fn log2(a: f64) callconv(.C) f64 {
return math.log2(a);
}
fn log2f(a: f32) callconv(.C) f32 {
return math.log2(a);
}
fn log10(a: f64) callconv(.C) f64 {
return math.log10(a);
}
fn log10f(a: f32) callconv(.C) f32 {
return math.log10(a);
}
fn fmodf(x: f32, y: f32) callconv(.C) f32 {
return generic_fmod(f32, x, y);
}
fn fmod(x: f64, y: f64) callconv(.C) f64 {
return generic_fmod(f64, x, y);
}
fn generic_fmod(comptime T: type, x: T, y: T) T {
@setRuntimeSafety(false);
const bits = @typeInfo(T).Float.bits;
const uint = std.meta.Int(.unsigned, bits);
const log2uint = math.Log2Int(uint);
const digits = if (T == f32) 23 else 52;
const exp_bits = if (T == f32) 9 else 12;
const bits_minus_1 = bits - 1;
const mask = if (T == f32) 0xff else 0x7ff;
var ux = @bitCast(uint, x);
var uy = @bitCast(uint, y);
var ex = @intCast(i32, (ux >> digits) & mask);
var ey = @intCast(i32, (uy >> digits) & mask);
const sx = if (T == f32) @intCast(u32, ux & 0x80000000) else @intCast(i32, ux >> bits_minus_1);
var i: uint = undefined;
if (uy << 1 == 0 or isNan(@bitCast(T, uy)) or ex == mask)
return (x * y) / (x * y);
if (ux << 1 <= uy << 1) {
if (ux << 1 == uy << 1)
return 0 * x;
return x;
}
// normalize x and y
if (ex == 0) {
i = ux << exp_bits;
while (i >> bits_minus_1 == 0) : ({
ex -= 1;
i <<= 1;
}) {}
ux <<= @intCast(log2uint, @bitCast(u32, -ex + 1));
} else {
ux &= maxInt(uint) >> exp_bits;
ux |= 1 << digits;
}
if (ey == 0) {
i = uy << exp_bits;
while (i >> bits_minus_1 == 0) : ({
ey -= 1;
i <<= 1;
}) {}
uy <<= @intCast(log2uint, @bitCast(u32, -ey + 1));
} else {
uy &= maxInt(uint) >> exp_bits;
uy |= 1 << digits;
}
// x mod y
while (ex > ey) : (ex -= 1) {
i = ux -% uy;
if (i >> bits_minus_1 == 0) {
if (i == 0)
return 0 * x;
ux = i;
}
ux <<= 1;
}
i = ux -% uy;
if (i >> bits_minus_1 == 0) {
if (i == 0)
return 0 * x;
ux = i;
}
while (ux >> digits == 0) : ({
ux <<= 1;
ex -= 1;
}) {}
// scale result up
if (ex > 0) {
ux -%= 1 << digits;
ux |= @as(uint, @bitCast(u32, ex)) << digits;
} else {
ux >>= @intCast(log2uint, @bitCast(u32, -ex + 1));
}
if (T == f32) {
ux |= sx;
} else {
ux |= @intCast(uint, sx) << bits_minus_1;
}
return @bitCast(T, ux);
}
test "fmod, fmodf" {
inline for ([_]type{ f32, f64 }) |T| {
const nan_val = math.nan(T);
const inf_val = math.inf(T);
try std.testing.expect(isNan(generic_fmod(T, nan_val, 1.0)));
try std.testing.expect(isNan(generic_fmod(T, 1.0, nan_val)));
try std.testing.expect(isNan(generic_fmod(T, inf_val, 1.0)));
try std.testing.expect(isNan(generic_fmod(T, 0.0, 0.0)));
try std.testing.expect(isNan(generic_fmod(T, 1.0, 0.0)));
try std.testing.expectEqual(@as(T, 0.0), generic_fmod(T, 0.0, 2.0));
try std.testing.expectEqual(@as(T, -0.0), generic_fmod(T, -0.0, 2.0));
try std.testing.expectEqual(@as(T, -2.0), generic_fmod(T, -32.0, 10.0));
try std.testing.expectEqual(@as(T, -2.0), generic_fmod(T, -32.0, -10.0));
try std.testing.expectEqual(@as(T, 2.0), generic_fmod(T, 32.0, 10.0));
try std.testing.expectEqual(@as(T, 2.0), generic_fmod(T, 32.0, -10.0));
}
}
fn sincos(a: f64, r_sin: *f64, r_cos: *f64) callconv(.C) void {
r_sin.* = math.sin(a);
r_cos.* = math.cos(a);
}
fn sincosf(a: f32, r_sin: *f32, r_cos: *f32) callconv(.C) void {
r_sin.* = math.sin(a);
r_cos.* = math.cos(a);
}
fn fabs(a: f64) callconv(.C) f64 {
return math.fabs(a);
}
fn fabsf(a: f32) callconv(.C) f32 {
return math.fabs(a);
}
fn roundf(a: f32) callconv(.C) f32 {
return math.round(a);
}
fn round(a: f64) callconv(.C) f64 {
return math.round(a);
}
fn roundl(a: c_longdouble) callconv(.C) c_longdouble {
if (!long_double_is_f128) {
@panic("TODO implement this");
}
return math.round(a);
}
fn fminf(x: f32, y: f32) callconv(.C) f32 {
return generic_fmin(f32, x, y);
}
fn fmin(x: f64, y: f64) callconv(.C) f64 {
return generic_fmin(f64, x, y);
}
fn generic_fmin(comptime T: type, x: T, y: T) T {
if (isNan(x))
return y;
if (isNan(y))
return x;
return if (x < y) x else y;
}
test "fmin, fminf" {
inline for ([_]type{ f32, f64 }) |T| {
const nan_val = math.nan(T);
try std.testing.expect(isNan(generic_fmin(T, nan_val, nan_val)));
try std.testing.expectEqual(@as(T, 1.0), generic_fmin(T, nan_val, 1.0));
try std.testing.expectEqual(@as(T, 1.0), generic_fmin(T, 1.0, nan_val));
try std.testing.expectEqual(@as(T, 1.0), generic_fmin(T, 1.0, 10.0));
try std.testing.expectEqual(@as(T, -1.0), generic_fmin(T, 1.0, -1.0));
}
}
fn fmaxf(x: f32, y: f32) callconv(.C) f32 {
return generic_fmax(f32, x, y);
}
fn fmax(x: f64, y: f64) callconv(.C) f64 {
return generic_fmax(f64, x, y);
}
fn generic_fmax(comptime T: type, x: T, y: T) T {
if (isNan(x))
return y;
if (isNan(y))
return x;
return if (x < y) y else x;
}
test "fmax, fmaxf" {
inline for ([_]type{ f32, f64 }) |T| {
const nan_val = math.nan(T);
try std.testing.expect(isNan(generic_fmax(T, nan_val, nan_val)));
try std.testing.expectEqual(@as(T, 1.0), generic_fmax(T, nan_val, 1.0));
try std.testing.expectEqual(@as(T, 1.0), generic_fmax(T, 1.0, nan_val));
try std.testing.expectEqual(@as(T, 10.0), generic_fmax(T, 1.0, 10.0));
try std.testing.expectEqual(@as(T, 1.0), generic_fmax(T, 1.0, -1.0));
}
}
// NOTE: The original code is full of implicit signed -> unsigned assumptions and u32 wraparound
// behaviour. Most intermediate i32 values are changed to u32 where appropriate but there are
// potentially some edge cases remaining that are not handled in the same way.
fn sqrt(x: f64) callconv(.C) f64 {
const tiny: f64 = 1.0e-300;
const sign: u32 = 0x80000000;
const u = @bitCast(u64, x);
var ix0 = @intCast(u32, u >> 32);
var ix1 = @intCast(u32, u & 0xFFFFFFFF);
// sqrt(nan) = nan, sqrt(+inf) = +inf, sqrt(-inf) = nan
if (ix0 & 0x7FF00000 == 0x7FF00000) {
return x * x + x;
}
// sqrt(+-0) = +-0
if (x == 0.0) {
return x;
}
// sqrt(-ve) = snan
if (ix0 & sign != 0) {
return math.snan(f64);
}
// normalize x
var m = @intCast(i32, ix0 >> 20);
if (m == 0) {
// subnormal
while (ix0 == 0) {
m -= 21;
ix0 |= ix1 >> 11;
ix1 <<= 21;
}
// subnormal
var i: u32 = 0;
while (ix0 & 0x00100000 == 0) : (i += 1) {
ix0 <<= 1;
}
m -= @intCast(i32, i) - 1;
ix0 |= ix1 >> @intCast(u5, 32 - i);
ix1 <<= @intCast(u5, i);
}
// unbias exponent
m -= 1023;
ix0 = (ix0 & 0x000FFFFF) | 0x00100000;
if (m & 1 != 0) {
ix0 += ix0 + (ix1 >> 31);
ix1 = ix1 +% ix1;
}
m >>= 1;
// sqrt(x) bit by bit
ix0 += ix0 + (ix1 >> 31);
ix1 = ix1 +% ix1;
var q: u32 = 0;
var q1: u32 = 0;
var s0: u32 = 0;
var s1: u32 = 0;
var r: u32 = 0x00200000;
var t: u32 = undefined;
var t1: u32 = undefined;
while (r != 0) {
t = s0 +% r;
if (t <= ix0) {
s0 = t + r;
ix0 -= t;
q += r;
}
ix0 = ix0 +% ix0 +% (ix1 >> 31);
ix1 = ix1 +% ix1;
r >>= 1;
}
r = sign;
while (r != 0) {
t1 = s1 +% r;
t = s0;
if (t < ix0 or (t == ix0 and t1 <= ix1)) {
s1 = t1 +% r;
if (t1 & sign == sign and s1 & sign == 0) {
s0 += 1;
}
ix0 -= t;
if (ix1 < t1) {
ix0 -= 1;
}
ix1 = ix1 -% t1;
q1 += r;
}
ix0 = ix0 +% ix0 +% (ix1 >> 31);
ix1 = ix1 +% ix1;
r >>= 1;
}
// rounding direction
if (ix0 | ix1 != 0) {
var z = 1.0 - tiny; // raise inexact
if (z >= 1.0) {
z = 1.0 + tiny;
if (q1 == 0xFFFFFFFF) {
q1 = 0;
q += 1;
} else if (z > 1.0) {
if (q1 == 0xFFFFFFFE) {
q += 1;
}
q1 += 2;
} else {
q1 += q1 & 1;
}
}
}
ix0 = (q >> 1) + 0x3FE00000;
ix1 = q1 >> 1;
if (q & 1 != 0) {
ix1 |= 0x80000000;
}
// NOTE: musl here appears to rely on signed twos-complement wraparound. +% has the same
// behaviour at least.
var iix0 = @intCast(i32, ix0);
iix0 = iix0 +% (m << 20);
const uz = (@intCast(u64, iix0) << 32) | ix1;
return @bitCast(f64, uz);
}
test "sqrt" {
const V = [_]f64{
0.0,
4.089288054930154,
7.538757127071935,
8.97780793672623,
5.304443821913729,
5.682408965311888,
0.5846878579110049,
3.650338664297043,
0.3178091951800732,
7.1505232436382835,
3.6589165881946464,
};
// Note that @sqrt will either generate the sqrt opcode (if supported by the
// target ISA) or a call to `sqrtf` otherwise.
for (V) |val|
try std.testing.expectEqual(@sqrt(val), sqrt(val));
}
test "sqrt special" {
try std.testing.expect(std.math.isPositiveInf(sqrt(std.math.inf(f64))));
try std.testing.expect(sqrt(0.0) == 0.0);
try std.testing.expect(sqrt(-0.0) == -0.0);
try std.testing.expect(isNan(sqrt(-1.0)));
try std.testing.expect(isNan(sqrt(std.math.nan(f64))));
}
fn sqrtf(x: f32) callconv(.C) f32 {
const tiny: f32 = 1.0e-30;
const sign: i32 = @bitCast(i32, @as(u32, 0x80000000));
var ix: i32 = @bitCast(i32, x);
if ((ix & 0x7F800000) == 0x7F800000) {
return x * x + x; // sqrt(nan) = nan, sqrt(+inf) = +inf, sqrt(-inf) = snan
}
// zero
if (ix <= 0) {
if (ix & ~sign == 0) {
return x; // sqrt (+-0) = +-0
}
if (ix < 0) {
return math.snan(f32);
}
}
// normalize
var m = ix >> 23;
if (m == 0) {
// subnormal
var i: i32 = 0;
while (ix & 0x00800000 == 0) : (i += 1) {
ix <<= 1;
}
m -= i - 1;
}
m -= 127; // unbias exponent
ix = (ix & 0x007FFFFF) | 0x00800000;
if (m & 1 != 0) { // odd m, double x to even
ix += ix;
}
m >>= 1; // m = [m / 2]
// sqrt(x) bit by bit
ix += ix;
var q: i32 = 0; // q = sqrt(x)
var s: i32 = 0;
var r: i32 = 0x01000000; // r = moving bit right -> left
while (r != 0) {
const t = s + r;
if (t <= ix) {
s = t + r;
ix -= t;
q += r;
}
ix += ix;
r >>= 1;
}
// floating add to find rounding direction
if (ix != 0) {
var z = 1.0 - tiny; // inexact
if (z >= 1.0) {
z = 1.0 + tiny;
if (z > 1.0) {
q += 2;
} else {
if (q & 1 != 0) {
q += 1;
}
}
}
}
ix = (q >> 1) + 0x3f000000;
ix += m << 23;
return @bitCast(f32, ix);
}
test "sqrtf" {
const V = [_]f32{
0.0,
4.089288054930154,
7.538757127071935,
8.97780793672623,
5.304443821913729,
5.682408965311888,
0.5846878579110049,
3.650338664297043,
0.3178091951800732,
7.1505232436382835,
3.6589165881946464,
};
// Note that @sqrt will either generate the sqrt opcode (if supported by the
// target ISA) or a call to `sqrtf` otherwise.
for (V) |val|
try std.testing.expectEqual(@sqrt(val), sqrtf(val));
}
test "sqrtf special" {
try std.testing.expect(std.math.isPositiveInf(sqrtf(std.math.inf(f32))));
try std.testing.expect(sqrtf(0.0) == 0.0);
try std.testing.expect(sqrtf(-0.0) == -0.0);
try std.testing.expect(isNan(sqrtf(-1.0)));
try std.testing.expect(isNan(sqrtf(std.math.nan(f32))));
}
// TODO we should be able to put this directly in std/linux/x86_64.zig but
// it causes a segfault in release mode. this is a workaround of calling it
// across .o file boundaries. fix comptime @ptrCast of nakedcc functions.
fn clone() callconv(.Naked) void {
switch (native_arch) {
.i386 => {
// __clone(func, stack, flags, arg, ptid, tls, ctid)
// +8, +12, +16, +20, +24, +28, +32
// syscall(SYS_clone, flags, stack, ptid, tls, ctid)
// eax, ebx, ecx, edx, esi, edi
asm volatile (
\\ push %%ebp
\\ mov %%esp,%%ebp
\\ push %%ebx
\\ push %%esi
\\ push %%edi
\\ // Setup the arguments
\\ mov 16(%%ebp),%%ebx
\\ mov 12(%%ebp),%%ecx
\\ and $-16,%%ecx
\\ sub $20,%%ecx
\\ mov 20(%%ebp),%%eax
\\ mov %%eax,4(%%ecx)
\\ mov 8(%%ebp),%%eax
\\ mov %%eax,0(%%ecx)
\\ mov 24(%%ebp),%%edx
\\ mov 28(%%ebp),%%esi
\\ mov 32(%%ebp),%%edi
\\ mov $120,%%eax
\\ int $128
\\ test %%eax,%%eax
\\ jnz 1f
\\ pop %%eax
\\ xor %%ebp,%%ebp
\\ call *%%eax
\\ mov %%eax,%%ebx
\\ xor %%eax,%%eax
\\ inc %%eax
\\ int $128
\\ hlt
\\1:
\\ pop %%edi
\\ pop %%esi
\\ pop %%ebx
\\ pop %%ebp
\\ ret
);
},
.x86_64 => {
asm volatile (
\\ xor %%eax,%%eax
\\ mov $56,%%al // SYS_clone
\\ mov %%rdi,%%r11
\\ mov %%rdx,%%rdi
\\ mov %%r8,%%rdx
\\ mov %%r9,%%r8
\\ mov 8(%%rsp),%%r10
\\ mov %%r11,%%r9
\\ and $-16,%%rsi
\\ sub $8,%%rsi
\\ mov %%rcx,(%%rsi)
\\ syscall
\\ test %%eax,%%eax
\\ jnz 1f
\\ xor %%ebp,%%ebp
\\ pop %%rdi
\\ call *%%r9
\\ mov %%eax,%%edi
\\ xor %%eax,%%eax
\\ mov $60,%%al // SYS_exit
\\ syscall
\\ hlt
\\1: ret
\\
);
},
.aarch64 => {
// __clone(func, stack, flags, arg, ptid, tls, ctid)
// x0, x1, w2, x3, x4, x5, x6
// syscall(SYS_clone, flags, stack, ptid, tls, ctid)
// x8, x0, x1, x2, x3, x4
asm volatile (
\\ // align stack and save func,arg
\\ and x1,x1,#-16
\\ stp x0,x3,[x1,#-16]!
\\
\\ // syscall
\\ uxtw x0,w2
\\ mov x2,x4
\\ mov x3,x5
\\ mov x4,x6
\\ mov x8,#220 // SYS_clone
\\ svc #0
\\
\\ cbz x0,1f
\\ // parent
\\ ret
\\ // child
\\1: ldp x1,x0,[sp],#16
\\ blr x1
\\ mov x8,#93 // SYS_exit
\\ svc #0