store: Wasm text instruction

Limited availability

This feature is not Baseline because it does not work in some of the most widely-used browsers.

The store memory instructions, are used to store a number on the stack in a memory.

There are store instructions for storing an i32, i64, f32, and f64 in memory. For the integer numbers, there are separate instruction variants for storing a wide typed number into a narrower number in memory. For example, you can store a 32-bit number into an 8-bit slot in memory using i32.store8. If the number doesn't fit in the narrower number type it will wrap. All the variants are listed below.

Try it

Syntax

Store in default memory

wasm

;; Store value in default memory at particular offset
i32.const 0 ;; stack variable with offset in memory to store the number
i32.const 20 ;; stack variable with the number to store
i32.store ;; store in default memory

;; Store using S-function (same values and offset)
(i32.store (i32.const 0) (i32.const 20))

Store to specified memory (if multi-memory supported)

wasm

;; Store in memory referenced by its index
i32.const 0 ;; offset in memory to store the number
i32.const 20 ;; the number to store
i32.store (memory 2)  ;; store in memory with index 2

;; Store in memory referenced by its name
i32.const 0 ;; offset to store the number
i32.const 20 ;; the number to store
i32.store (memory $memoryName)  ;; store in memory with name "$memoryName"

;; Store in same memory using an S function
(i32.store (memory $memoryName) (i32.const 0) (i32.const 20))

Instructions and opcodes

Instruction	Binary opcode
`i32.store`	`0x36`
`i64.store`	`0x37`
`f32.store`	`0x38`
`f64.store`	`0x39`
`i32.store8`	`0x3a`
`i32.store16`	`0x3b`
`i64.store8`	`0x3c`
`i64.store16`	`0x3d`
`i64.store32`	`0x3e`

Specifications

Specification
Unknown specification # syntax-instr-memory

Browser compatibility

BCD tables only load in the browser

Note: Memory support in Wasm modules matches the WebAssembly.Memory JavaScript API. The multiMemory key indicates versions in which store can be used with a specified memory.