if / else

if consumes an i32 condition (0 = false, non-zero = true). Both branches must match result types when present.

(module
  (func (param $x i32) (result i32)
    (if (result i32) (i32.eqz (local.get $x))
      (then (i32.const 1))
      (else (i32.const 0))))
)

• Use (result t) to push a value from either branch.
• Omit else when the block produces no result.

Instruction Reference

• Control Flow Instructions — block, loop, if, br, br_if