Files
zig/test/behavior/bitcast.zig
T
Matthew Lugg 10d523f068 Air.Legalize: fix typo in bitcast legalization
A typo meant that the legalization of vector `@bitCast` was literally
just not considering the operand. Oops!

We had a behavior test which should have caught this, but it wasn't
really testing the right thing, so failed to do so. I've updated it to
test what it's supposed to test, so it fails before this patch and
passes after this patch.

Resolves: https://github.com/ziglang/zig/issues/26008
2026-03-19 15:41:22 +00:00

561 lines
19 KiB
Zig

const std = @import("std");
const builtin = @import("builtin");
const assert = std.debug.assert;
const expect = std.testing.expect;
const expectEqual = std.testing.expectEqual;
const math = std.math;
const maxInt = std.math.maxInt;
const minInt = std.math.minInt;
const native_endian = builtin.target.cpu.arch.endian();
test "@bitCast iX -> uX (32, 64)" {
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
const bit_values = [_]usize{ 32, 64 };
inline for (bit_values) |bits| {
try testBitCast(bits);
try comptime testBitCast(bits);
}
}
test "@bitCast iX -> uX (8, 16, 128)" {
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
const bit_values = [_]usize{ 8, 16, 128 };
inline for (bit_values) |bits| {
try testBitCast(bits);
try comptime testBitCast(bits);
}
}
test "@bitCast iX -> uX exotic integers" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
const bit_values = [_]usize{ 1, 48, 27, 512, 493, 293, 125, 204, 112 };
inline for (bit_values) |bits| {
try testBitCast(bits);
try comptime testBitCast(bits);
}
}
fn testBitCast(comptime N: usize) !void {
const iN = std.meta.Int(.signed, N);
const uN = std.meta.Int(.unsigned, N);
try expect(conv_iN(N, -1) == maxInt(uN));
try expect(conv_uN(N, maxInt(uN)) == -1);
try expect(conv_iN(N, maxInt(iN)) == maxInt(iN));
try expect(conv_uN(N, maxInt(iN)) == maxInt(iN));
try expect(conv_uN(N, 1 << (N - 1)) == minInt(iN));
try expect(conv_iN(N, minInt(iN)) == (1 << (N - 1)));
try expect(conv_uN(N, 0) == 0);
try expect(conv_iN(N, 0) == 0);
if (N > 24) {
try expect(conv_uN(N, 0xf23456) == 0xf23456);
}
}
fn conv_iN(comptime N: usize, x: std.meta.Int(.signed, N)) std.meta.Int(.unsigned, N) {
return @as(std.meta.Int(.unsigned, N), @bitCast(x));
}
fn conv_uN(comptime N: usize, x: std.meta.Int(.unsigned, N)) std.meta.Int(.signed, N) {
return @as(std.meta.Int(.signed, N), @bitCast(x));
}
test "bitcast uX to bytes" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
const bit_values = [_]usize{ 1, 48, 27, 512, 493, 293, 125, 204, 112 };
inline for (bit_values) |bits| {
try testBitCast(bits);
try comptime testBitCast(bits);
}
}
fn testBitCastuXToBytes(comptime N: usize) !void {
// The location of padding bits in these layouts are technically not defined
// by LLVM, but we currently allow exotic integers to be cast (at comptime)
// to types that expose their padding bits anyway.
//
// This test at least makes sure those bits are matched by the runtime behavior
// on the platforms we target. If the above behavior is restricted after all,
// this test should be deleted.
const T = std.meta.Int(.unsigned, N);
for ([_]T{ 0, ~@as(T, 0) }) |init_value| {
var x: T = init_value;
const bytes = std.mem.asBytes(&x);
const byte_count = (N + 7) / 8;
switch (native_endian) {
.little => {
var byte_i = 0;
while (byte_i < (byte_count - 1)) : (byte_i += 1) {
try expect(bytes[byte_i] == 0xff);
}
try expect(((bytes[byte_i] ^ 0xff) << -%@as(u3, @truncate(N))) == 0);
},
.big => {
var byte_i = byte_count - 1;
while (byte_i > 0) : (byte_i -= 1) {
try expect(bytes[byte_i] == 0xff);
}
try expect(((bytes[byte_i] ^ 0xff) << -%@as(u3, @truncate(N))) == 0);
},
}
}
}
test "nested bitcast" {
const S = struct {
fn moo(x: isize) !void {
try expect(@as(isize, @intCast(42)) == x);
}
fn foo(x: isize) !void {
try @This().moo(
@as(isize, @bitCast(if (x != 0) @as(usize, @bitCast(x)) else @as(usize, @bitCast(x)))),
);
}
};
try S.foo(42);
try comptime S.foo(42);
}
// issue #3010: compiler segfault
test "bitcast literal [4]u8 param to u32" {
const ip = @as(u32, @bitCast([_]u8{ 255, 255, 255, 255 }));
try expect(ip == maxInt(u32));
}
test "bitcast generates a temporary value" {
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
var y: u16 = 0x55AA;
_ = &y;
const x: u16 = @bitCast(@as([2]u8, @bitCast(y)));
try expect(y == x);
}
test "@bitCast packed structs at runtime and comptime" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
const Full = packed struct {
number: u16,
};
const Divided = packed struct {
half1: u8,
quarter3: u4,
quarter4: u4,
};
const S = struct {
fn doTheTest() !void {
var full = Full{ .number = 0x1234 };
_ = &full;
const two_halves: Divided = @bitCast(full);
try expect(two_halves.half1 == 0x34);
try expect(two_halves.quarter3 == 0x2);
try expect(two_halves.quarter4 == 0x1);
}
};
try S.doTheTest();
try comptime S.doTheTest();
}
test "@bitCast extern structs at runtime and comptime" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
const Full = extern struct {
number: u16,
};
const TwoHalves = extern struct {
half1: u8,
half2: u8,
};
const S = struct {
fn doTheTest() !void {
var full = Full{ .number = 0x1234 };
_ = &full;
const two_halves: TwoHalves = @bitCast(full);
switch (native_endian) {
.big => {
try expect(two_halves.half1 == 0x12);
try expect(two_halves.half2 == 0x34);
},
.little => {
try expect(two_halves.half1 == 0x34);
try expect(two_halves.half2 == 0x12);
},
}
}
};
try S.doTheTest();
try comptime S.doTheTest();
}
test "bitcast packed struct to integer and back" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
const LevelUpMove = packed struct {
move_id: u9,
level: u7,
};
const S = struct {
fn doTheTest() !void {
var move = LevelUpMove{ .move_id = 1, .level = 2 };
_ = &move;
const v: u16 = @bitCast(move);
const back_to_a_move: LevelUpMove = @bitCast(v);
try expect(back_to_a_move.move_id == 1);
try expect(back_to_a_move.level == 2);
}
};
try S.doTheTest();
try comptime S.doTheTest();
}
test "implicit cast to error union by returning" {
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
const S = struct {
fn entry() !void {
try expect((func(-1) catch unreachable) == maxInt(u64));
}
pub fn func(sz: i64) anyerror!u64 {
return @as(u64, @bitCast(sz));
}
};
try S.entry();
try comptime S.entry();
}
test "bitcast packed struct literal to byte" {
const Foo = packed struct {
value: u8,
};
const casted = @as(u8, @bitCast(Foo{ .value = 0xF }));
try expect(casted == 0xf);
}
test "comptime bitcast used in expression has the correct type" {
const Foo = packed struct {
value: u8,
};
try expect(@as(u8, @bitCast(Foo{ .value = 0xF })) == 0xf);
}
test "bitcast passed as tuple element" {
const S = struct {
fn foo(args: anytype) !void {
comptime assert(@TypeOf(args[0]) == f32);
try expect(args[0] == 12.34);
}
};
try S.foo(.{@as(f32, @bitCast(@as(u32, 0x414570A4)))});
}
test "triple level result location with bitcast sandwich passed as tuple element" {
const S = struct {
fn foo(args: anytype) !void {
comptime assert(@TypeOf(args[0]) == f64);
try expect(args[0] > 12.33 and args[0] < 12.35);
}
};
try S.foo(.{@as(f64, @as(f32, @bitCast(@as(u32, 0x414570A4))))});
}
test "@bitCast packed struct of floats" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
const Foo = packed struct {
a: f16 = 0,
b: f32 = 1,
c: f64 = 2,
d: f128 = 3,
};
const Foo2 = packed struct {
a: f16 = 0,
b: f32 = 1,
c: f64 = 2,
d: f128 = 3,
};
const S = struct {
fn doTheTest() !void {
var foo = Foo{};
_ = &foo;
const v: Foo2 = @bitCast(foo);
try expect(v.a == foo.a);
try expect(v.b == foo.b);
try expect(v.c == foo.c);
try expect(v.d == foo.d);
}
};
try S.doTheTest();
try comptime S.doTheTest();
}
test "comptime @bitCast packed struct to int and back" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
const S = packed struct {
void: void = {},
uint: u8 = 13,
uint_bit_aligned: u3 = 2,
iint_pos: i4 = 1,
iint_neg4: i3 = -4,
iint_neg2: i3 = -2,
float: f32 = 3.14,
@"enum": enum(u2) { A, B = 1, C, D } = .B,
};
const Int = @typeInfo(S).@"struct".backing_integer.?;
// S -> Int
var s: S = .{};
_ = &s;
try expectEqual(@as(Int, @bitCast(s)), comptime @as(Int, @bitCast(S{})));
// Int -> S
var i: Int = 0;
_ = &i;
const rt_cast = @as(S, @bitCast(i));
const ct_cast = comptime @as(S, @bitCast(@as(Int, 0)));
inline for (@typeInfo(S).@"struct".fields) |field| {
try expectEqual(@field(rt_cast, field.name), @field(ct_cast, field.name));
}
}
test "comptime bitcast with fields following f80" {
if (true) {
// https://github.com/ziglang/zig/issues/19387
return error.SkipZigTest;
}
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_sparc64) return error.SkipZigTest; // TODO
const FloatT = extern struct { f: f80, x: u128 align(16) };
const x: FloatT = .{ .f = 0.5, .x = 123 };
var x_as_uint: u256 = comptime @as(u256, @bitCast(x));
_ = &x_as_uint;
try expect(x.f == @as(FloatT, @bitCast(x_as_uint)).f);
try expect(x.x == @as(FloatT, @bitCast(x_as_uint)).x);
}
test "bitcast vector to integer and back" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.cpu.arch.endian() == .big and builtin.zig_backend == .stage2_llvm) return error.SkipZigTest;
var vec: @Vector(16, bool) = @splat(true);
vec[1] = false;
const int: u16 = @bitCast(vec);
try expect(int == 0b1111_1111_1111_1101);
const vec_again: @Vector(16, bool) = @bitCast(int);
try expect(vec_again[0]);
try expect(!vec_again[1]);
try expect(vec_again[2]);
try expect(vec_again[3]);
try expect(vec_again[4]);
try expect(vec_again[5]);
try expect(vec_again[6]);
try expect(vec_again[7]);
try expect(vec_again[8]);
try expect(vec_again[9]);
try expect(vec_again[10]);
try expect(vec_again[11]);
try expect(vec_again[12]);
try expect(vec_again[13]);
try expect(vec_again[14]);
try expect(vec_again[15]);
const int_again: u16 = @bitCast(vec_again);
try expect(int_again == 0b1111_1111_1111_1101);
}
fn bitCastWrapper16(x: f16) u16 {
return @as(u16, @bitCast(x));
}
fn bitCastWrapper32(x: f32) u32 {
return @as(u32, @bitCast(x));
}
fn bitCastWrapper64(x: f64) u64 {
return @as(u64, @bitCast(x));
}
fn bitCastWrapper128(x: f128) u128 {
return @as(u128, @bitCast(x));
}
test "bitcast nan float does not modify signaling bit" {
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_llvm and builtin.cpu.arch.isPowerPC()) return error.SkipZigTest;
const snan_u16: u16 = 0x7D00;
const snan_u32: u32 = 0x7FA00000;
const snan_u64: u64 = 0x7FF4000000000000;
const snan_u128: u128 = 0x7FFF4000000000000000000000000000;
// 16 bit
const snan_f16_const = math.snan(f16);
try expectEqual(snan_u16, @as(u16, @bitCast(snan_f16_const)));
try expectEqual(snan_u16, bitCastWrapper16(snan_f16_const));
var snan_f16_var = math.snan(f16);
_ = &snan_f16_var;
try expectEqual(snan_u16, @as(u16, @bitCast(snan_f16_var)));
try expectEqual(snan_u16, bitCastWrapper16(snan_f16_var));
// 32 bit
const snan_f32_const = math.snan(f32);
try expectEqual(snan_u32, @as(u32, @bitCast(snan_f32_const)));
try expectEqual(snan_u32, bitCastWrapper32(snan_f32_const));
var snan_f32_var = math.snan(f32);
_ = &snan_f32_var;
try expectEqual(snan_u32, @as(u32, @bitCast(snan_f32_var)));
try expectEqual(snan_u32, bitCastWrapper32(snan_f32_var));
// 64 bit
const snan_f64_const = math.snan(f64);
try expectEqual(snan_u64, @as(u64, @bitCast(snan_f64_const)));
try expectEqual(snan_u64, bitCastWrapper64(snan_f64_const));
var snan_f64_var = math.snan(f64);
_ = &snan_f64_var;
try expectEqual(snan_u64, @as(u64, @bitCast(snan_f64_var)));
try expectEqual(snan_u64, bitCastWrapper64(snan_f64_var));
// 128 bit
const snan_f128_const = math.snan(f128);
try expectEqual(snan_u128, @as(u128, @bitCast(snan_f128_const)));
try expectEqual(snan_u128, bitCastWrapper128(snan_f128_const));
var snan_f128_var = math.snan(f128);
_ = &snan_f128_var;
try expectEqual(snan_u128, @as(u128, @bitCast(snan_f128_var)));
try expectEqual(snan_u128, bitCastWrapper128(snan_f128_var));
}
test "@bitCast of packed struct of bools all true" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_riscv64) return error.SkipZigTest; // TODO
const P = packed struct {
b0: bool,
b1: bool,
b2: bool,
b3: bool,
};
var p = std.mem.zeroes(P);
p.b0 = true;
p.b1 = true;
p.b2 = true;
p.b3 = true;
try expect(@as(u8, @as(u4, @bitCast(p))) == 15);
}
test "@bitCast of packed struct of bools all false" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest; // TODO
const P = packed struct {
b0: bool,
b1: bool,
b2: bool,
b3: bool,
};
var p = std.mem.zeroes(P);
p.b0 = false;
p.b1 = false;
p.b2 = false;
p.b3 = false;
try expect(@as(u8, @as(u4, @bitCast(p))) == 0);
}
test "@bitCast of extern struct containing pointer" {
if (builtin.zig_backend == .stage2_aarch64) return error.SkipZigTest;
if (builtin.zig_backend == .stage2_arm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_c) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_wasm) return error.SkipZigTest; // TODO
if (builtin.zig_backend == .stage2_spirv) return error.SkipZigTest; // TODO
const S = struct {
const A = extern struct {
ptr: *const u32,
};
const B = extern struct {
ptr: *const i32,
};
fn doTheTest() !void {
const x: u32 = 123;
var a: A = undefined;
a = .{ .ptr = &x };
const b: B = @bitCast(a);
try expect(b.ptr.* == 123);
}
};
try S.doTheTest();
try comptime S.doTheTest();
}