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even tighter return type for std.math.sign (#31485)

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The code in #31475 does not return the "smallest integer type that fits possible values" for very small integer types, namely `u0`, `i0`, and `i1` - which all end up with a return type one bit too long. Fixed in this commit.

Reviewed-on: https://codeberg.org/ziglang/zig/pulls/31485
Reviewed-by: Andrew Kelley <andrew@ziglang.org>
Co-authored-by: Hila Friedman <red.black.liquorice@gmail.com>
Co-committed-by: Hila Friedman <red.black.liquorice@gmail.com>
This commit is contained in:
Hila Friedman
2026-03-17 02:10:27 +01:00
committed by Andrew Kelley
parent 097ca369d5
commit bfd2cc5a3f
1 changed files with 5 additions and 12 deletions
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lib/std/math.zig
+5 -12
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@@ -1775,10 +1775,7 @@ pub const F80 = struct {
fn SignOf(T: type) type {
return switch (@typeInfo(T)) {
.comptime_int, .comptime_float => comptime_int,
.int => |int| switch (int.signedness) {
.signed => IntFittingRange(-1, 1),
.unsigned => IntFittingRange(0, 1),
},
.int => IntFittingRange(@max(minInt(T), -1), @min(maxInt(T), 1)),
.float => IntFittingRange(-1, 1),
.vector => |vec| @Vector(vec.len, SignOf(vec.child)),
else => @compileError("Expected an int, float, or a vector of one, found " ++ @typeName(T)),
@@ -1792,14 +1789,10 @@ fn SignOf(T: type) type {
/// Branchless.
pub inline fn sign(n: anytype) SignOf(@TypeOf(n)) {
const T = SignOf(@TypeOf(n));
return switch (@typeInfo(T)) {
.vector => |vec| blk: {
const zero: T = @splat(0);
const one: T = @splat(1);
break :blk @select(vec.child, n > zero, one, zero) - @select(vec.child, n < zero, one, zero);
},
else => @as(T, @intFromBool(n > 0)) - @as(T, @intFromBool(n < 0)),
};
const zero: T = if (@typeInfo(T) == .vector) @splat(0) else 0;
const pos: T = @intCast(@intFromBool(n > zero));
const neg: T = @intCast(@intFromBool(n < zero));
return pos - neg;
}
fn testSign() !void {