WebAssembly Operators

What are Operators in WebAssembly?

In WebAssembly, operators are instructions executed on values pushed to the stack. Since WebAssembly is a stack-based language, all operations take their operands from the stack and push the results back onto the stack.

Operators are divided into several categories based on their functionality:

1. Arithmetic Operators
2. Comparison Operators
3. Logical Operators
4. Bitwise Operators
5. Memory Operators
6. Control Flow Operators

1. Arithmetic Operators

Arithmetic operators perform basic mathematical calculations like addition, subtraction, multiplication, and division. They are type-specific (i32, i64, f32, f64).

Common Arithmetic Operators:

Operator	Description	Example in WebAssembly
i32.add	Adds two 32-bit integers	5 + 3 = 8
i64.sub	Subtracts two 64-bit integers	10 – 7 = 3
f32.mul	Multiplies two 32-bit floats	4.5 * 2.0 = 9.0
f64.div	Divides two 64-bit floats	8.0 – 2.0 = 4.0

Example:

(module
  (func $addNumbers (param $a i32) (param $b i32) (result i32)
    local.get $a     ;; Push $a onto the stack
    local.get $b     ;; Push $b onto the stack
    i32.add          ;; Add the two values
  )
  (export "addNumbers" (func $addNumbers))
)

2. Comparison Operators

Comparison operators evaluate two values and return a boolean result (0 for false, 1 for true). They are used for equality and relational checks.

Common Comparison Operators:

Operator	Description	Example in WebAssembly
i32.EQ	Checks if two values are equal	5 == 5 -> 1
i32.ne	Checks if two values are not equal	4 != 5 -> 1
i32.it_s	Checks if the first is less than the second (signed)	3 < 5 -> 1
i64.gt_u	Checks if the first is greater than the second (unsigned)	7 > 3 -> 1

Example:

(module
  (func $compareValues (param $x i32) (param $y i32) (result i32)
    local.get $x     ;; Push $x onto the stack
    local.get $y     ;; Push $y onto the stack
    i32.eq           ;; Compare $x and $y for equality
  )
  (export "compareValues" (func $compareValues))
)

3. Logical Operators

Logical operators are used for Boolean logic operations like AND, OR and NOT.

Common Logical Operators:

Operator	Description	Example in WebAssembly
i32.and	Logical AND	1 AND 0 -> 0
i32.or	Logical OR	1 OR 0 -> 1
i32.xor	Logical XOR (exclusive OR)	1 XOR 1 -> 0

Example:

(module
  (func $logicalAnd (param $a i32) (param $b i32) (result i32)
    local.get $a     ;; Push $a onto the stack
    local.get $b     ;; Push $b onto the stack
    i32.and          ;; Perform AND operation
  )
  (export "logicalAnd" (func $logicalAnd))
)

4. Bitwise Operators

Bitwise operators manipulate individual bits of integer values.

Common Bitwise Operators:

Operator	Description	Example in WebAssembly
i32.shl	Left shift	4 << 1 -> 8
i32.shr_u	Right shift (unsigned)	8 >> 1 -> 4
i32.shr_s	Right shift (signed)	-8 >> 1 -> -4

Example:

(module
  (func $bitwiseShift (param $x i32) (result i32)
    local.get $x     ;; Push $x onto the stack
    i32.const 1      ;; Push the shift count
    i32.shl          ;; Perform left shift
  )
  (export "bitwiseShift" (func $bitwiseShift))
)

5. Memory Operators

Memory operators interact with the linear memory of the WebAssembly module.

Common Memory Operators:

Operator	Description	Example
i32.load	Loads a 32-bit value from memory	load from memory
i32.store	Stores a 32-bit value into memory	Store to memory

Example:

(module
  (memory $mem 1) ;; Define a memory block
  (func $storeValue
    i32.const 0    ;; Push the memory offset
    i32.const 42   ;; Push the value to store
    i32.store      ;; Store the value in memory
  )
  (func $loadValue (result i32)
    i32.const 0    ;; Push the memory offset
    i32.load       ;; Load the value from memory
  )
  (export "storeValue" (func $storeValue))
  (export "loadValue" (func $loadValue))
)

6. Control Flow Operators

Control flow operators manage the execution flow of the program, such as loops and conditionals.

Common Control Flow Operators:

Operator	Description
block	Defines a block of instructions
loop	Defines a loop
if	Executes instructions conditionally
br	Breaks out of a block or loop

Example:

(module
  (func $conditionalCheck (param $x i32) (result i32)
    local.get $x
    i32.const 10
    i32.lt_s
    if (result i32)
      i32.const 1   ;; Return 1 if $x < 10
    else
      i32.const 0   ;; Return 0 otherwise
    end
  )
  (export "conditionalCheck" (func $conditionalCheck))
)