.. index:: ! changes
.. _changes:

Change History
--------------

Since the original release 1.0 of the WebAssembly specification, a number of proposals for extensions have been integrated.
The following sections provide an overview of what has changed.

Release 2.0
~~~~~~~~~~~

.. index:: instruction, integer

Sign extension instructions
...........................

Added new numeric instructions for performing sign extension within integer representations [#proposal-signext]_.

* New :ref:`numeric instructions <syntax-instr-numeric>`: :math:`\K{i}\X{nn}\K{.}\EXTEND\X{N}\K{\_s}`


.. index:: instruction, trap, floating-point, integer

Non-trapping float-to-int conversions
.....................................

Added new conversion instructions that avoid trapping when converting a floating-point number to an integer [#proposal-cvtsat]_.

* New :ref:`numeric instructions <syntax-instr-numeric>`: :math:`\K{i}\X{nn}\K{.}\TRUNC\K{\_sat\_f}\X{mm}\K{\_}\sx`


.. index:: block, function, value type, result type

Multiple values
...............

Generalized the result type of blocks and functions to allow for multiple values; in addition, introduced the ability to have block parameters [#proposal-multivalue]_.

* :ref:`Function types <syntax-functype>` allow more than one result

* :ref:`Block types <syntax-blocktype>` can be arbitrary function types


.. index:: value type, reference, reference type, instruction, element segment

Reference types
...............

Added |FUNCREF| and |EXTERNREF| as new value types and respective instructions [#proposal-reftype]_.

* New :ref:`value types <syntax-valtype>`: :ref:`reference types <syntax-reftype>` |FUNCREF| and |EXTERNREF|

* New :ref:`reference instructions <syntax-instr-ref>`: |REFNULL|, |REFFUNC|, |REFISNULL|

* Enrich :ref:`parametric instruction <syntax-instr-parametric>`: |SELECT| with optional type immediate

* New :ref:`declarative <syntax-elemmode>` form of :ref:`element segment <syntax-elem>`


.. index:: reference, instruction, table, table type

Table instructions
..................

Added instructions to directly access and modify tables [#proposal-reftype]_.

* :ref:`Table types <syntax-tabletype>` allow any :ref:`reference type <syntax-reftype>` as element type

* New :ref:`table instructions <syntax-instr-table>`: |TABLEGET|, |TABLESET|, |TABLESIZE|, |TABLEGROW|


.. index:: table, instruction, table index, element segment

Multiple tables
...............

Added the ability to use multiple tables per module [#proposal-reftype]_.

* :ref:`Modules <syntax-module>` may :ref:`define <syntax-table>`, :ref:`import <syntax-import>`, and :ref:`export <syntax-export>` multiple tables

* :ref:`Table instructions <syntax-instr-table>` take a :ref:`table index <syntax-tableidx>` immediate: |TABLEGET|, |TABLESET|, |TABLESIZE|, |TABLEGROW|, |CALLINDIRECT|

* :ref:`Element segments <syntax-elem>` take a :ref:`table index <syntax-tableidx>`


.. index:: instruction, table, memory, data segment, element segment

Bulk memory and table instructions
..................................

Added instructions that modify ranges of memory or table entries [#proposal-reftype]_ [#proposal-bulk]_

* New :ref:`memory instructions <syntax-instr-memory>`: |MEMORYFILL|, |MEMORYINIT|, |MEMORYCOPY|, |DATADROP|

* New :ref:`table instructions <syntax-instr-table>`: |TABLEFILL|, |TABLEINIT|, |TABLECOPY|, |ELEMDROP|

* New :ref:`passive <syntax-datamode>` form of :ref:`data segment <syntax-data>`

* New :ref:`passive <syntax-elemmode>` form of :ref:`element segment <syntax-elem>`

* New :ref:`data count section <binary-datacountsec>` in binary format

* Active data and element segments boundaries are no longer checked at compile time but may trap instead


.. index:: instructions, SIMD, value type, vector type

Vector instructions
...................

Added vector type and instructions that manipulate multiple numeric values in parallel (also known as *SIMD*, single instruction multiple data) [#proposal-vectype]_

* New :ref:`value type <syntax-valtype>`: |V128|

* New :ref:`memory instructions <syntax-instr-memory>`: :math:`\K{v128.}\LOAD`, :math:`\K{v128.}\LOAD{}\!N\!\K{x}\!M\!\K{\_}\sx`, :math:`\K{v128.}\LOAD{}N\K{\_zero}`, :math:`\K{v128.}\LOAD{}N\K{\_splat}`, :math:`\K{v128.}\LOAD{}N\K{\_lane}`, :math:`\K{v128.}\STORE`, :math:`\K{v128.}\STORE{}N\K{\_lane}`

* New constant :ref:`vector instruction <syntax-instr-vec>`: :math:`\K{v128.}\VCONST`

* New unary :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{v128.not}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.abs}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.neg}`, :math:`\K{i8x16.popcnt}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.abs}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.neg}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.sqrt}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.ceil}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.floor}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.trunc}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.nearest}`

* New binary :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{v128.and}`, :math:`\K{v128.andnot}`, :math:`\K{v128.or}`, :math:`\K{v128.xor}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.add}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.sub}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.mul}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.add\_sat\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.sub\_sat\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.min\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.max\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.shl}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.shr\_}\sx`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.add}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.extmul\_}\half\K{\_i}\!N'\!\K{x}\!M'\!\K{\_}\sx`, :math:`\K{i16x8.q15mulr\_sat\_s}`, :math:`\K{i32x4.dot\_i16x8\_s}`, :math:`\K{i16x8.extadd\_pairwise\_i8x16\_}\sx`, :math:`\K{i32x4.extadd\_pairwise\_i16x8\_}\sx`, :math:`\K{i8x16.avgr\_u}`, :math:`\K{i16x8.avgr\_u}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.sub}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.mul}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.div}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.min}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.max}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.pmin}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.pmax}`

* New ternary :ref:`vector instruction <syntax-instr-vec>`: :math:`\K{v128.bitselect}`

* New test :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{v128.any\_true}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.all\_true}`

* New relational :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{i}\!N\!\K{x}\!M\!\K{.eq}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.ne}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.lt\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.gt\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.le\_}\sx`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.ge\_}\sx`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.eq}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.ne}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.lt}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.gt}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.le}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.ge}`

* New conversion :ref:`vector instructions <syntax-instr-vec>`::math:`\K{i32x4.trunc\_sat\_f32x4\_}\sx`, :math:`\K{i32x4.trunc\_sat\_f64x2\_}\sx\K{\_zero}`, :math:`\K{f32x4.convert\_i32x4\_}\sx`, :math:`\K{f32x4.demote\_f64x2\_zero}`, :math:`\K{f64x2.convert\_low\_i32x4\_}\sx`, :math:`\K{f64x2.promote\_low\_f32x4}`

* New lane access :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{i}\!N\!\K{x}\!M\!\K{.extract\_lane\_}\sx^?`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.replace\_lane}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.extract\_lane}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.replace\_lane}`

* New lane splitting/combining :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{i}\!N\!\K{x}\!M\!\K{.extend\_}\half\K{\_i}\!N'\!\K{x}\!M'\!\K{\_}\sx`, :math:`\K{i8x16.narrow\_i16x8\_}\sx`, :math:`\K{i16x8.narrow\_i32x4\_}\sx`

* New byte reordering :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{i8x16.shuffle}`, :math:`\K{i8x16.swizzle}`

* New injection/projection :ref:`vector instructions <syntax-instr-vec>`: :math:`\K{i}\!N\!\K{x}\!M\!\K{.splat}`, :math:`\K{f}\!N\!\K{x}\!M\!\K{.splat}`, :math:`\K{i}\!N\!\K{x}\!M\!\K{.bitmask}`


.. [#proposal-signext]
   https://github.com/WebAssembly/spec/tree/main/proposals/sign-extension-ops/

.. [#proposal-cvtsat]
   https://github.com/WebAssembly/spec/tree/main/proposals/nontrapping-float-to-int-conversion/

.. [#proposal-multivalue]
   https://github.com/WebAssembly/spec/tree/main/proposals/multi-value/

.. [#proposal-reftype]
   https://github.com/WebAssembly/spec/tree/main/proposals/reference-types/

.. [#proposal-bulk]
   https://github.com/WebAssembly/spec/tree/main/proposals/bulk-memory-operations/

.. [#proposal-vectype]
   https://github.com/WebAssembly/spec/tree/main/proposals/simd/