diff options
| author | Luke Wagner <mail@lukewagner.name> | 2017-01-10 13:15:40 -1000 |
|---|---|---|
| committer | GitHub <noreply@github.com> | 2017-01-10 13:15:40 -1000 |
| commit | 2d8626f15126d080ce5e63e20bf280c451ea4dc3 (patch) | |
| tree | 32438c61b62b36ac75f91961122a1335f60d1904 /BinaryEncoding.md | |
| parent | c6f9f700392d6f36e34a992d180a30da00bd5bef (diff) | |
| download | nanowasm-design-2d8626f15126d080ce5e63e20bf280c451ea4dc3.tar.gz | |
Describe instruction opcode encoding scheme (#926)
* Describe instruction opcode encoding scheme
* Not actually 'far' fewer
Diffstat (limited to 'BinaryEncoding.md')
| -rw-r--r-- | BinaryEncoding.md | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/BinaryEncoding.md b/BinaryEncoding.md index c1c1a0c..799f529 100644 --- a/BinaryEncoding.md +++ b/BinaryEncoding.md @@ -53,6 +53,15 @@ represented by _at most_ ceil(_N_/7) bytes that may contain padding `0x80` or `0 Note: Currently, the only sizes used are `varint7`, `varint32` and `varint64`. +## Instruction Opcodes + +In the MVP, the opcodes of [instructions](Semantics.md) are all encoded in a +single byte since there are fewer than 256 opcodes. Future features like +[SIMD](FutureFeatures.md#fixed-width-simd) and [atomics](FutureFeatures.md#threads) +will bring the total count above 256 and so an extension scheme will be +necessary, designating one or more single-byte values as prefixes for multi-byte +opcodes. + ## Language Types All types are distinguished by a negative `varint7` values that is the first byte of their encoding (representing a type constructor): @@ -456,7 +465,9 @@ count may be greater or less than the actual number of locals. # Function Bodies Function bodies consist of a sequence of local variable declarations followed by -[bytecode instructions](Semantics.md). Each function body must end with the `end` opcode. +[bytecode instructions](Semantics.md). Instructions are encoded as an +[opcode](#instruction-opcodes) followed by zero or more *immediates* as defined +by the tables below. Each function body must end with the `end` opcode. | Field | Type | Description | | ----- | ---- | ----------- | |