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std/math: add support for vectors to rotl()/rotr()

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Frank Denis 2020-10-29 10:08:50 +01:00 committed by Andrew Kelley
parent b3314a8be6
commit bb3dfd2708
1 changed files with 20 additions and 3 deletions
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23
lib/std/math.zig
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@ -405,7 +405,14 @@ test "math.shr" {
/// Rotates right. Only unsigned values can be rotated.
/// Negative shift values results in shift modulo the bit count.
pub fn rotr(comptime T: type, x: T, r: anytype) T {
if (@typeInfo(T).Int.is_signed) {
if (@typeInfo(T) == .Vector) {
const C = @typeInfo(T).Vector.child;
if (@typeInfo(C).Int.is_signed) {
@compileError("cannot rotate signed integers");
}
const ar = @intCast(Log2Int(C), @mod(r, @typeInfo(C).Int.bits));
return (x >> @splat(@typeInfo(T).Vector.len, ar)) | (x << @splat(@typeInfo(T).Vector.len, 1 + ~ar));
} else if (@typeInfo(T).Int.is_signed) {
@compileError("cannot rotate signed integer");
} else {
const ar = @mod(r, @typeInfo(T).Int.bits);
@ -419,12 +426,21 @@ test "math.rotr" {
testing.expect(rotr(u8, 0b00000001, @as(usize, 8)) == 0b00000001);
testing.expect(rotr(u8, 0b00000001, @as(usize, 4)) == 0b00010000);
testing.expect(rotr(u8, 0b00000001, @as(isize, -1)) == 0b00000010);
testing.expect(rotr(std.meta.Vector(1, u32), std.meta.Vector(1, u32){1}, @as(usize, 1))[0] == @as(u32, 1) << 31);
testing.expect(rotr(std.meta.Vector(1, u32), std.meta.Vector(1, u32){1}, @as(isize, -1))[0] == @as(u32, 1) << 1);
}
/// Rotates left. Only unsigned values can be rotated.
/// Negative shift values results in shift modulo the bit count.
pub fn rotl(comptime T: type, x: T, r: anytype) T {
if (@typeInfo(T).Int.is_signed) {
if (@typeInfo(T) == .Vector) {
const C = @typeInfo(T).Vector.child;
if (@typeInfo(C).Int.is_signed) {
@compileError("cannot rotate signed integers");
}
const ar = @intCast(Log2Int(C), @mod(r, @typeInfo(C).Int.bits));
return (x << @splat(@typeInfo(T).Vector.len, ar)) | (x >> @splat(@typeInfo(T).Vector.len, 1 +% ~ar));
} else if (@typeInfo(T).Int.is_signed) {
@compileError("cannot rotate signed integer");
} else {
const ar = @mod(r, @typeInfo(T).Int.bits);
@ -438,6 +454,8 @@ test "math.rotl" {
testing.expect(rotl(u8, 0b00000001, @as(usize, 8)) == 0b00000001);
testing.expect(rotl(u8, 0b00000001, @as(usize, 4)) == 0b00010000);
testing.expect(rotl(u8, 0b00000001, @as(isize, -1)) == 0b10000000);
testing.expect(rotl(std.meta.Vector(1, u32), std.meta.Vector(1, u32){1 << 31}, @as(usize, 1))[0] == 1);
testing.expect(rotl(std.meta.Vector(1, u32), std.meta.Vector(1, u32){1 << 31}, @as(isize, -1))[0] == @as(u32, 1) << 30);
}
pub fn Log2Int(comptime T: type) type {
@ -1141,4 +1159,3 @@ test "math.comptime" {
comptime const v = sin(@as(f32, 1)) + ln(@as(f32, 5));
testing.expect(v == sin(@as(f32, 1)) + ln(@as(f32, 5)));
}