Web Assembly WAT Reference

You will find all the instructions used in the WAT programming language.

Variables

Instruction	Description
(local...)	Create a local variable.
local.get	Push a local variable onto the stack.
local.set	Pop a value off the stack and set a local variable.
local.tee	Pop a value off the stack and set a local variable, but keeps the value on the stack.
(global...)	Create a global variable.
global.get	Push a global variable onto the stack.
global.set	Pop a value off the stack and set a global variable.

Basics

Instruction	Description
(module...)	Create the WASM module.
(func...)	Create a function.
call	Call a function.
(param...)	Declare a parameter to a code block.
(result...)	Declare a result to be returned for a code block.
return	Return out of a function.
(if...)	Create an if...then...else block.
(loop...)	Create a looping code block.
(block...)	Create a code block you can exit.
br	Branch to the top of a loop or the bottom or a block.
br_if	Branch if a condition was met.
br_table	Branch a list of code blocks.

Tables

Instruction	Description
(table...)	Create the a table of function references.
table.get	Get a reference to a function from a table.
table.set	Set a reference to a function into a table.
table.size	Gets number of elements in a table.
table.grow	Increase the number of elements a table contains.
table.fill	Fill a table with the a set value.
table.copy	Copy functions references from one table to another.
table.init	Copy functions references from data into a table.
(type...)	Declares what parameters and result data types a function uses.
call_indirect	Declare a table's function references.
(element...)	Declare a collection of function references.
elem.drop	Remove a passive element data block from memory.
ref.null	Push a NULL reference for a function onto the stack.
ref.is_null	Check to see if a reference to a function is NULL or not.
ref.func	Push a reference to a function onto the stack.

Memory

Instruction	Description
(memory...)	Create the a memory area.
memory.size	Gets size (number of pages) the memory currently has.
memory.grow	Increase the size of the memory (in pages).
memory.fill	Fill an area of memory with a set value.
memory.copy	Copy one area of memory to another.
memory.init	Copy passive data into memory.
(data...)	Declare a block of constant data that can be copied into memory.
data.drop	Remove a passive data block from memory.

Miscellaneous

Instruction	Description
(start...)	Set which function to call when the WASM module starts up.
nop	Do nothing.
unreachable	Declare an area in code that should be unreachable and throw an exception if reached.
drop	Pop a value off the stack and do nothing with it.
select	Select between two items depending on a condition.

JavaScript

Instruction	Description
(import...)	Import information from JavaScript into WASM.
(export...)	Export information to JavaScript from within WASM.
(tag...)	Information about exceptions that can be thrown.
throw	Throw an exception to be catched within JavaScript.
WebAssembly.Global	JavaScript global object.
WebAssembly.Memory	JavaScript memory object.
WebAssembly.Tag	JavaScript tag object.