Skip to content

Latest commit

 

History

History
84 lines (54 loc) · 1.69 KB

const.md

File metadata and controls

84 lines (54 loc) · 1.69 KB
Raw

const (declare constant)

Declares a numeric constant value (of type i32, i64, f32, or f64), placing it on the stack 1

There are four different opcodes, to indicate the type of the value 2

$$ T.\mathsf{const} \enspace const_T \enspace ( \enspace ) \to T $$

Instructions

Opcode Instruction Immediates Stack Arity
0x41 i32.const $\mathsf{i32}$ $[ ] \to [ \mathsf{i32} ]$
0x42 i64.const $\mathsf{i64}$ $[ ] \to [ \mathsf{i64} ]$
0x43 f32.const $\mathsf{f32}$ $[ ] \to [ \mathsf{f32} ]$
0x44 f64.const $\mathsf{f64}$ $[ ] \to [ \mathsf{f64} ]$

!!! {.info} For SIMD / Vectors, see v128.const !!!

WAT Examples

Adding two constants

;; Places 10 on the stack
i32.const 10

;; Places 20 on the stack
i32.const 20

;; Takes two values off of the stack (10 and 20), adds them, and
;; places the result (30) on the stack
i32.add

Different ways to declare integers

i32.const 10
i32.const +20
i64.const -30

;; Integers can also be declared using hex format
i32.const 0x6D

Different ways to declare floats

f32.const 30.5
f32.const +32.57
f64.const -41.99

f64.const 12.34e+40

;; Hex-Float Format
f64.const 0x1p-1

;; Infinity
f64.const inf

;; NaN
f64.const nan
f64.const nan:0x123

References

WebAssembly Core Specification

Footnotes

  1. Execution, Numeric Instructions, const - https://www.w3.org/TR/wasm-core-2/exec/instructions.html#exec-const ↩

  2. Structure, Numeric Instructions - https://www.w3.org/TR/wasm-core-2/syntax/instructions.html#numeric-instructions ↩