cubecl_core/frontend/operation/
branch.rs

1use cubecl_macros::intrinsic;
2
3use crate as cubecl;
4use crate::prelude::{CubePrimitive, Vector};
5use crate::{
6    ir::{Operator, Scope, SelectOperands},
7    prelude::*,
8};
9
10/// Executes both branches, *then* selects a value based on the condition. This *should* be
11/// branchless, but might depend on the compiler.
12///
13/// # Safety
14///
15/// Since both branches are *evaluated* regardless of the condition, both branches must be *valid*
16/// regardless of the condition. Illegal memory accesses should not be done in either branch.
17pub fn select<C: CubePrimitive>(condition: bool, then: C, or_else: C) -> C {
18    if condition { then } else { or_else }
19}
20
21/// Same as [`select()`] but with vectors instead.
22#[cube]
23pub fn select_many<C: Scalar, N: Size>(
24    condition: Vector<bool, N>,
25    then: Vector<C, N>,
26    or_else: Vector<C, N>,
27) -> Vector<C, N> {
28    intrinsic!(|scope| select::expand(scope, condition.expand.into(), then, or_else))
29}
30
31pub mod select {
32    use cubecl_ir::ValueKind;
33
34    use crate::ir::Instruction;
35
36    use super::*;
37
38    pub fn expand<C: CubePrimitive>(
39        scope: &Scope,
40        condition: NativeExpand<bool>,
41        then: NativeExpand<C>,
42        or_else: NativeExpand<C>,
43    ) -> NativeExpand<C> {
44        let cond = condition.expand;
45
46        if let ValueKind::Constant(value) = cond.kind {
47            if value.as_bool() {
48                return then;
49            } else {
50                return or_else;
51            }
52        }
53
54        let then = then.expand;
55        let or_else = or_else.expand;
56
57        let vf = cond.vector_size();
58        let vf = Ord::max(vf, then.vector_size());
59        let vf = Ord::max(vf, or_else.vector_size());
60
61        let output = scope.create_value(then.value_type().with_vector_size(vf));
62
63        let select = Operator::Select(SelectOperands {
64            cond,
65            then,
66            or_else,
67        });
68        scope.register(Instruction::new(select, output));
69
70        output.into()
71    }
72}
cubecl_core/frontend/operation/branch.rs

cubecl_core/frontend/operation/
branch.rs
