Binary encoding of SIMD

This document describes the binary encoding of the SIMD value type and instructions.

SIMD value type

The v128 value type is encoded as 0x7b:

valtype ::= ...
          | 0x7B => v128

SIMD instruction encodings

All SIMD instructions are encoded as a 0xfd prefix byte followed by a SIMD-specific opcode in LEB128 format:

instr ::= ...
        | 0xFD simdop:varuint32 ...

Some SIMD instructions have additional immediate operands following simdop. These immediate operands are encoded as individual bytes. For example, the i8x16.shuffle instruction has 16 bytes after simdop.

In the description below, ImmLaneIdx{I} indicates the maximum value of the byte. For example, ImmLaneIdx16 is a byte with values in the range 0-15 (inclusive).

Instruction	`simdop`	Immediate operands
`v128.load`	`0x00`	m:memarg
`v128.load8x8_s`	`0x01`	m:memarg
`v128.load8x8_u`	`0x02`	m:memarg
`v128.load16x4_s`	`0x03`	m:memarg
`v128.load16x4_u`	`0x04`	m:memarg
`v128.load32x2_s`	`0x05`	m:memarg
`v128.load32x2_u`	`0x06`	m:memarg
`v128.load8_splat`	`0x07`	m:memarg
`v128.load16_splat`	`0x08`	m:memarg
`v128.load32_splat`	`0x09`	m:memarg
`v128.load64_splat`	`0x0a`	m:memarg
`v128.store`	`0x0b`	m:memarg
`v128.const`	`0x0c`	i:ImmByte[16]
`i8x16.shuffle`	`0x0d`	s:ImmLaneIdx32[16]
`i8x16.swizzle`	`0x0e`	-
`i8x16.splat`	`0x0f`	-
`i16x8.splat`	`0x10`	-
`i32x4.splat`	`0x11`	-
`i64x2.splat`	`0x12`	-
`f32x4.splat`	`0x13`	-
`f64x2.splat`	`0x14`	-
`i8x16.extract_lane_s`	`0x15`	i:ImmLaneIdx16
`i8x16.extract_lane_u`	`0x16`	i:ImmLaneIdx16
`i8x16.replace_lane`	`0x17`	i:ImmLaneIdx16
`i16x8.extract_lane_s`	`0x18`	i:ImmLaneIdx8
`i16x8.extract_lane_u`	`0x19`	i:ImmLaneIdx8
`i16x8.replace_lane`	`0x1a`	i:ImmLaneIdx8
`i32x4.extract_lane`	`0x1b`	i:ImmLaneIdx4
`i32x4.replace_lane`	`0x1c`	i:ImmLaneIdx4
`i64x2.extract_lane`	`0x1d`	i:ImmLaneIdx2
`i64x2.replace_lane`	`0x1e`	i:ImmLaneIdx2
`f32x4.extract_lane`	`0x1f`	i:ImmLaneIdx4
`f32x4.replace_lane`	`0x20`	i:ImmLaneIdx4
`f64x2.extract_lane`	`0x21`	i:ImmLaneIdx2
`f64x2.replace_lane`	`0x22`	i:ImmLaneIdx2
`i8x16.eq`	`0x23`	-
`i8x16.ne`	`0x24`	-
`i8x16.lt_s`	`0x25`	-
`i8x16.lt_u`	`0x26`	-
`i8x16.gt_s`	`0x27`	-
`i8x16.gt_u`	`0x28`	-
`i8x16.le_s`	`0x29`	-
`i8x16.le_u`	`0x2a`	-
`i8x16.ge_s`	`0x2b`	-
`i8x16.ge_u`	`0x2c`	-
`i16x8.eq`	`0x2d`	-
`i16x8.ne`	`0x2e`	-
`i16x8.lt_s`	`0x2f`	-
`i16x8.lt_u`	`0x30`	-
`i16x8.gt_s`	`0x31`	-
`i16x8.gt_u`	`0x32`	-
`i16x8.le_s`	`0x33`	-
`i16x8.le_u`	`0x34`	-
`i16x8.ge_s`	`0x35`	-
`i16x8.ge_u`	`0x36`	-
`i32x4.eq`	`0x37`	-
`i32x4.ne`	`0x38`	-
`i32x4.lt_s`	`0x39`	-
`i32x4.lt_u`	`0x3a`	-
`i32x4.gt_s`	`0x3b`	-
`i32x4.gt_u`	`0x3c`	-
`i32x4.le_s`	`0x3d`	-
`i32x4.le_u`	`0x3e`	-
`i32x4.ge_s`	`0x3f`	-
`i32x4.ge_u`	`0x40`	-
`f32x4.eq`	`0x41`	-
`f32x4.ne`	`0x42`	-
`f32x4.lt`	`0x43`	-
`f32x4.gt`	`0x44`	-
`f32x4.le`	`0x45`	-
`f32x4.ge`	`0x46`	-
`f64x2.eq`	`0x47`	-
`f64x2.ne`	`0x48`	-
`f64x2.lt`	`0x49`	-
`f64x2.gt`	`0x4a`	-
`f64x2.le`	`0x4b`	-
`f64x2.ge`	`0x4c`	-
`v128.not`	`0x4d`	-
`v128.and`	`0x4e`	-
`v128.andnot`	`0x4f`	-
`v128.or`	`0x50`	-
`v128.xor`	`0x51`	-
`v128.bitselect`	`0x52`	-
`i8x16.abs`	`0x60`	-
`i8x16.neg`	`0x61`	-
`i8x16.all_true`	`0x63`	-
`i8x16.bitmask`	`0x64`	-
`i8x16.narrow_i16x8_s`	`0x65`	-
`i8x16.narrow_i16x8_u`	`0x66`	-
`i8x16.shl`	`0x6b`	-
`i8x16.shr_s`	`0x6c`	-
`i8x16.shr_u`	`0x6d`	-
`i8x16.add`	`0x6e`	-
`i8x16.add_sat_s`	`0x6f`	-
`i8x16.add_sat_u`	`0x70`	-
`i8x16.sub`	`0x71`	-
`i8x16.sub_sat_s`	`0x72`	-
`i8x16.sub_sat_u`	`0x73`	-
`i8x16.min_s`	`0x76`	-
`i8x16.min_u`	`0x77`	-
`i8x16.max_s`	`0x78`	-
`i8x16.max_u`	`0x79`	-
`i8x16.avgr_u`	`0x7b`	-
`i16x8.abs`	`0x80`	-
`i16x8.neg`	`0x81`	-
`i16x8.all_true`	`0x83`	-
`i16x8.bitmask`	`0x84`	-
`i16x8.narrow_i32x4_s`	`0x85`	-
`i16x8.narrow_i32x4_u`	`0x86`	-
`i16x8.extend_low_i8x16_s`	`0x87`	-
`i16x8.extend_high_i8x16_s`	`0x88`	-
`i16x8.extend_low_i8x16_u`	`0x89`	-
`i16x8.extend_high_i8x16_u`	`0x8a`	-
`i16x8.shl`	`0x8b`	-
`i16x8.shr_s`	`0x8c`	-
`i16x8.shr_u`	`0x8d`	-
`i16x8.add`	`0x8e`	-
`i16x8.add_sat_s`	`0x8f`	-
`i16x8.add_sat_u`	`0x90`	-
`i16x8.sub`	`0x91`	-
`i16x8.sub_sat_s`	`0x92`	-
`i16x8.sub_sat_u`	`0x93`	-
`i16x8.mul`	`0x95`	-
`i16x8.min_s`	`0x96`	-
`i16x8.min_u`	`0x97`	-
`i16x8.max_s`	`0x98`	-
`i16x8.max_u`	`0x99`	-
`i16x8.avgr_u`	`0x9b`	-
`i32x4.abs`	`0xa0`	-
`i32x4.neg`	`0xa1`	-
`i32x4.all_true`	`0xa3`	-
`i32x4.bitmask`	`0xa4`	-
`i32x4.extend_low_i16x8_s`	`0xa7`	-
`i32x4.extend_high_i16x8_s`	`0xa8`	-
`i32x4.extend_low_i16x8_u`	`0xa9`	-
`i32x4.extend_high_i16x8_u`	`0xaa`	-
`i32x4.shl`	`0xab`	-
`i32x4.shr_s`	`0xac`	-
`i32x4.shr_u`	`0xad`	-
`i32x4.add`	`0xae`	-
`i32x4.sub`	`0xb1`	-
`i32x4.mul`	`0xb5`	-
`i32x4.min_s`	`0xb6`	-
`i32x4.min_u`	`0xb7`	-
`i32x4.max_s`	`0xb8`	-
`i32x4.max_u`	`0xb9`	-
`i32x4.dot_i16x8_s`	`0xba`	-
`i64x2.abs`	`0xc0`	-
`i64x2.neg`	`0xc1`	-
`i64x2.bitmask`	`0xc4`	-
`i64x2.extend_low_i32x4_s`	`0xc7`	-
`i64x2.extend_high_i32x4_s`	`0xc8`	-
`i64x2.extend_low_i32x4_u`	`0xc9`	-
`i64x2.extend_high_i32x4_u`	`0xca`	-
`i64x2.shl`	`0xcb`	-
`i64x2.shr_s`	`0xcc`	-
`i64x2.shr_u`	`0xcd`	-
`i64x2.add`	`0xce`	-
`i64x2.sub`	`0xd1`	-
`i64x2.mul`	`0xd5`	-
`f32x4.ceil`	`0x67`	-
`f32x4.floor`	`0x68`	-
`f32x4.trunc`	`0x69`	-
`f32x4.nearest`	`0x6a`	-
`f64x2.ceil`	`0x74`	-
`f64x2.floor`	`0x75`	-
`f64x2.trunc`	`0x7a`	-
`f64x2.nearest`	`0x94`	-
`f32x4.abs`	`0xe0`	-
`f32x4.neg`	`0xe1`	-
`f32x4.sqrt`	`0xe3`	-
`f32x4.add`	`0xe4`	-
`f32x4.sub`	`0xe5`	-
`f32x4.mul`	`0xe6`	-
`f32x4.div`	`0xe7`	-
`f32x4.min`	`0xe8`	-
`f32x4.max`	`0xe9`	-
`f32x4.pmin`	`0xea`	-
`f32x4.pmax`	`0xeb`	-
`f64x2.abs`	`0xec`	-
`f64x2.neg`	`0xed`	-
`f64x2.sqrt`	`0xef`	-
`f64x2.add`	`0xf0`	-
`f64x2.sub`	`0xf1`	-
`f64x2.mul`	`0xf2`	-
`f64x2.div`	`0xf3`	-
`f64x2.min`	`0xf4`	-
`f64x2.max`	`0xf5`	-
`f64x2.pmin`	`0xf6`	-
`f64x2.pmax`	`0xf7`	-
`i32x4.trunc_sat_f32x4_s`	`0xf8`	-
`i32x4.trunc_sat_f32x4_u`	`0xf9`	-
`f32x4.convert_i32x4_s`	`0xfa`	-
`f32x4.convert_i32x4_u`	`0xfb`	-
`v128.load32_zero`	`0x5c`	m:memarg
`v128.load64_zero`	`0x5d`	m:memarg
`i16x8.extmul_low_i8x16_s`	`0x9c`	-
`i16x8.extmul_high_i8x16_s`	`0x9d`	-
`i16x8.extmul_low_i8x16_u`	`0x9e`	-
`i16x8.extmul_high_i8x16_u`	`0x9f`	-
`i32x4.extmul_low_i16x8_s`	`0xbc`	-
`i32x4.extmul_high_i16x8_s`	`0xbd`	-
`i32x4.extmul_low_i16x8_u`	`0xbe`	-
`i32x4.extmul_high_i16x8_u`	`0xbf`	-
`i64x2.extmul_low_i32x4_s`	`0xdc`	-
`i64x2.extmul_high_i32x4_s`	`0xdd`	-
`i64x2.extmul_low_i32x4_u`	`0xde`	-
`i64x2.extmul_high_i32x4_u`	`0xdf`	-
`i16x8.q15mulr_sat_s`	`0x82`	-
`v128.any_true`	`0x53`	-
`v128.load8_lane`	`0x54`	m:memarg, i:ImmLaneIdx16
`v128.load16_lane`	`0x55`	m:memarg, i:ImmLaneIdx8
`v128.load32_lane`	`0x56`	m:memarg, i:ImmLaneIdx4
`v128.load64_lane`	`0x57`	m:memarg, i:ImmLaneIdx2
`v128.store8_lane`	`0x58`	m:memarg, i:ImmLaneIdx16
`v128.store16_lane`	`0x59`	m:memarg, i:ImmLaneIdx8
`v128.store32_lane`	`0x5a`	m:memarg, i:ImmLaneIdx4
`v128.store64_lane`	`0x5b`	m:memarg, i:ImmLaneIdx2
`i64x2.eq`	`0xd6`	-
`i64x2.ne`	`0xd7`	-
`i64x2.lt_s`	`0xd8`	-
`i64x2.gt_s`	`0xd9`	-
`i64x2.le_s`	`0xda`	-
`i64x2.ge_s`	`0xdb`	-
`i64x2.all_true`	`0xc3`	-
`f64x2.convert_low_i32x4_s`	`0xfe`	-
`f64x2.convert_low_i32x4_u`	`0xff`	-
`i32x4.trunc_sat_f64x2_s_zero`	`0xfc`	-
`i32x4.trunc_sat_f64x2_u_zero`	`0xfd`	-
`f32x4.demote_f64x2_zero`	`0x5e`	-
`f64x2.promote_low_f32x4`	`0x5f`	-
`i8x16.popcnt`	`0x62`	-
`i16x8.extadd_pairwise_i8x16_s`	`0x7c`	-
`i16x8.extadd_pairwise_i8x16_u`	`0x7d`	-
`i32x4.extadd_pairwise_i16x8_s`	`0x7e`	-
`i32x4.extadd_pairwise_i16x8_u`	`0x7f`	-

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BinarySIMD.md

BinarySIMD.md

Binary encoding of SIMD

SIMD value type

SIMD instruction encodings

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Binary encoding of SIMD

SIMD value type

SIMD instruction encodings