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Merge pull request #1330 from ethereum/assemblyDef
Assembly definition.
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#################
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Solidity Assembly
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#################
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.. index:: ! assembly, ! asm, ! evmasm
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Solidity defines an assembly language that can also be used without Solidity.
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This assembly language can also be used as "inline assembly" inside Solidity
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source code. We start with describing how to use inline assembly and how it
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differs from standalone assembly and then specify assembly itself.
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TODO: Write about how scoping rules of inline assembly are a bit different
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and the complications that arise when for example using internal functions
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of libraries. Furhermore, write about the symbols defined by the compiler.
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Inline Assembly
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===============
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For more fine-grained control especially in order to enhance the language by writing libraries,
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it is possible to interleave Solidity statements with inline assembly in a language close
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to the one of the virtual machine. Due to the fact that the EVM is a stack machine, it is
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often hard to address the correct stack slot and provide arguments to opcodes at the correct
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point on the stack. Solidity's inline assembly tries to facilitate that and other issues
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arising when writing manual assembly by the following features:
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* functional-style opcodes: ``mul(1, add(2, 3))`` instead of ``push1 3 push1 2 add push1 1 mul``
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* assembly-local variables: ``let x := add(2, 3) let y := mload(0x40) x := add(x, y)``
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* access to external variables: ``function f(uint x) { assembly { x := sub(x, 1) } }``
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* labels: ``let x := 10 repeat: x := sub(x, 1) jumpi(repeat, eq(x, 0))``
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* loops: ``for { let i := 0 } lt(i, x) { i := add(i, 1) } { y := mul(2, y) }``
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* switch statements: ``switch x case 0: { y := mul(x, 2) } default: { y := 0 }``
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* function calls: ``function f(x) -> (y) { switch x case 0: { y := 1 } default: { y := mul(x, f(sub(x, 1))) } }``
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.. note::
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Of the above, loops, function calls and switch statements are not yet implemented.
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We now want to describe the inline assembly language in detail.
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.. warning::
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Inline assembly is still a relatively new feature and might change if it does not prove useful,
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so please try to keep up to date.
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Example
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-------
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The following example provides library code to access the code of another contract and
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load it into a ``bytes`` variable. This is not possible at all with "plain Solidity" and the
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idea is that assembly libraries will be used to enhance the language in such ways.
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.. code::
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library GetCode {
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function at(address _addr) returns (bytes o_code) {
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assembly {
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// retrieve the size of the code, this needs assembly
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let size := extcodesize(_addr)
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// allocate output byte array - this could also be done without assembly
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// by using o_code = new bytes(size)
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o_code := mload(0x40)
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// new "memory end" including padding
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mstore(0x40, add(o_code, and(add(add(size, 0x20), 0x1f), not(0x1f))))
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// store length in memory
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mstore(o_code, size)
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// actually retrieve the code, this needs assembly
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extcodecopy(_addr, add(o_code, 0x20), 0, size)
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}
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}
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}
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Inline assembly could also be beneficial in cases where the optimizer fails to produce
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efficient code. Please be aware that assembly is much more difficult to write because
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the compiler does not perform checks, so you should use it only if
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you really know what you are doing.
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.. code::
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library VectorSum {
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// This function is less efficient because the optimizer currently fails to
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// remove the bounds checks in array access.
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function sumSolidity(uint[] _data) returns (uint o_sum) {
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for (uint i = 0; i < _data.length; ++i)
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o_sum += _data[i];
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}
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// We know that we only access the array in bounds, so we can avoid the check.
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// 0x20 needs to be added to an array because the first slot contains the
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// array length.
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function sumAsm(uint[] _data) returns (uint o_sum) {
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for (uint i = 0; i < _data.length; ++i) {
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assembly {
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o_sum := mload(add(add(_data, 0x20), mul(i, 0x20)))
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}
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}
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}
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}
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Syntax
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------
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Assembly parses comments, literals and identifiers exactly as Solidity, so you can use the
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usual ``//`` and ``/* */`` comments. Inline assembly is marked by ``assembly { ... }`` and inside
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these curly braces, the following can be used (see the later sections for more details)
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- literals, i.e. ``0x123``, ``42`` or ``"abc"`` (strings up to 32 characters)
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- opcodes (in "instruction style"), e.g. ``mload sload dup1 sstore``, for a list see below
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- opcode in functional style, e.g. ``add(1, mlod(0))``
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- labels, e.g. ``name:``
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- variable declarations, e.g. ``let x := 7`` or ``let x := add(y, 3)``
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- identifiers (labels or assembly-local variables and externals if used as inline assembly), e.g. ``jump(name)``, ``3 x add``
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- assignments (in "instruction style"), e.g. ``3 =: x``
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- assignments in functional style, e.g. ``x := add(y, 3)``
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- blocks where local variables are scoped inside, e.g. ``{ let x := 3 { let y := add(x, 1) } }``
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Opcodes
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-------
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This document does not want to be a full description of the Ethereum virtual machine, but the
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following list can be used as a reference of its opcodes.
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If an opcode takes arguments (always from the top of the stack), they are given in parentheses.
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Note that the order of arguments can be seed to be reversed in non-functional style (explained below).
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Opcodes marked with ``-`` do not push an item onto the stack, those marked with ``*`` are
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special and all others push exactly one item onte the stack.
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In the following, ``mem[a...b)`` signifies the bytes of memory starting at position ``a`` up to
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(excluding) position ``b`` and ``storage[p]`` signifies the storage contents at position ``p``.
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The opcodes ``pushi`` and ``jumpdest`` cannot be used directly.
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In the grammar, opcodes are represented as pre-defined identifiers.
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+-------------------------+------+-----------------------------------------------------------------+
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| stop + `-` | stop execution, identical to return(0,0) |
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+-------------------------+------+-----------------------------------------------------------------+
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| add(x, y) | | x + y |
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+-------------------------+------+-----------------------------------------------------------------+
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| sub(x, y) | | x - y |
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+-------------------------+------+-----------------------------------------------------------------+
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| mul(x, y) | | x * y |
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+-------------------------+------+-----------------------------------------------------------------+
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| div(x, y) | | x / y |
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+-------------------------+------+-----------------------------------------------------------------+
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| sdiv(x, y) | | x / y, for signed numbers in two's complement |
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+-------------------------+------+-----------------------------------------------------------------+
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| mod(x, y) | | x % y |
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+-------------------------+------+-----------------------------------------------------------------+
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| smod(x, y) | | x % y, for signed numbers in two's complement |
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+-------------------------+------+-----------------------------------------------------------------+
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| exp(x, y) | | x to the power of y |
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+-------------------------+------+-----------------------------------------------------------------+
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| not(x) | | ~x, every bit of x is negated |
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+-------------------------+------+-----------------------------------------------------------------+
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| lt(x, y) | | 1 if x < y, 0 otherwise |
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+-------------------------+------+-----------------------------------------------------------------+
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| gt(x, y) | | 1 if x > y, 0 otherwise |
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+-------------------------+------+-----------------------------------------------------------------+
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| slt(x, y) | | 1 if x < y, 0 otherwise, for signed numbers in two's complement |
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+-------------------------+------+-----------------------------------------------------------------+
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| sgt(x, y) | | 1 if x > y, 0 otherwise, for signed numbers in two's complement |
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+-------------------------+------+-----------------------------------------------------------------+
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| eq(x, y) | | 1 if x == y, 0 otherwise |
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+-------------------------+------+-----------------------------------------------------------------+
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| iszero(x) | | 1 if x == 0, 0 otherwise |
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+-------------------------+------+-----------------------------------------------------------------+
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| and(x, y) | | bitwise and of x and y |
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+-------------------------+------+-----------------------------------------------------------------+
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| or(x, y) | | bitwise or of x and y |
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+-------------------------+------+-----------------------------------------------------------------+
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| xor(x, y) | | bitwise xor of x and y |
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+-------------------------+------+-----------------------------------------------------------------+
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| byte(n, x) | | nth byte of x, where the most significant byte is the 0th byte |
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+-------------------------+------+-----------------------------------------------------------------+
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| addmod(x, y, m) | | (x + y) % m with arbitrary precision arithmetics |
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+-------------------------+------+-----------------------------------------------------------------+
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| mulmod(x, y, m) | | (x * y) % m with arbitrary precision arithmetics |
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+-------------------------+------+-----------------------------------------------------------------+
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| signextend(i, x) | | sign extend from (i*8+7)th bit counting from least significant |
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+-------------------------+------+-----------------------------------------------------------------+
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| sha3(p, n) | | keccak(mem[p...(p+n))) |
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+-------------------------+------+-----------------------------------------------------------------+
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| jump(label) | `-` | jump to label / code position |
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+-------------------------+------+-----------------------------------------------------------------+
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| jumpi(label, cond) | `-` | jump to label if cond is nonzero |
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+-------------------------+------+-----------------------------------------------------------------+
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| pc | | current position in code |
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+-------------------------+------+-----------------------------------------------------------------+
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| pop | `*` | remove topmost stack slot |
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+-------------------------+------+-----------------------------------------------------------------+
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| dup1 ... dup16 | | copy ith stack slot to the top (counting from top) |
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+-------------------------+------+-----------------------------------------------------------------+
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| swap1 ... swap16 | `*` | swap topmost and ith stack slot below it |
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+-------------------------+------+-----------------------------------------------------------------+
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| mload(p) | | mem[p..(p+32)) |
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+-------------------------+------+-----------------------------------------------------------------+
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| mstore(p, v) | `-` | mem[p..(p+32)) := v |
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+-------------------------+------+-----------------------------------------------------------------+
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| mstore8(p, v) | `-` | mem[p] := v & 0xff - only modifies a single byte |
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+-------------------------+------+-----------------------------------------------------------------+
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| sload(p) | | storage[p] |
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+-------------------------+------+-----------------------------------------------------------------+
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| sstore(p, v) | `-` | storage[p] := v |
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+-------------------------+------+-----------------------------------------------------------------+
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| msize | | size of memory, i.e. largest accessed memory index |
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+-------------------------+------+-----------------------------------------------------------------+
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| gas | | gas still available to execution |
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+-------------------------+------+-----------------------------------------------------------------+
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| address | | address of the current contract / execution context |
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+-------------------------+------+-----------------------------------------------------------------+
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| balance(a) | | wei balance at address a |
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+-------------------------+------+-----------------------------------------------------------------+
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| caller | | call sender (excluding delegatecall) |
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+-------------------------+------+-----------------------------------------------------------------+
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| callvalue | | wei sent together with the current call |
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+-------------------------+------+-----------------------------------------------------------------+
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| calldataload(p) | | call data starting from position p (32 bytes) |
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+-------------------------+------+-----------------------------------------------------------------+
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| calldatasize | | size of call data in bytes |
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+-------------------------+------+-----------------------------------------------------------------+
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| calldatacopy(t, f, s) | `-` | copy s bytes from calldata at position f to mem at position t |
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+-------------------------+------+-----------------------------------------------------------------+
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| codesize | | size of the code of the current contract / execution context |
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+-------------------------+------+-----------------------------------------------------------------+
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| codecopy(t, f, s) | `-` | copy s bytes from code at position f to mem at position t |
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+-------------------------+------+-----------------------------------------------------------------+
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| extcodesize(a) | | size of the code at address a |
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+-------------------------+------+-----------------------------------------------------------------+
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| extcodecopy(a, t, f, s) | `-` | like codecopy(t, f, s) but take code at address a |
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+-------------------------+------+-----------------------------------------------------------------+
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| create(v, p, s) | | create new contract with code mem[p..(p+s)) and send v wei |
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| | | and return the new address |
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+-------------------------+------+-----------------------------------------------------------------+
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| call(g, a, v, in, | | call contract at address a with input mem[in..(in+insize)] |
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| insize, out, outsize) | | providing g gas and v wei and output area |
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| | | mem[out..(out+outsize)] returting 1 on error (out of gas) |
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+-------------------------+------+-----------------------------------------------------------------+
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| callcode(g, a, v, in, | | identical to call but only use the code from a and stay |
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| insize, out, outsize) | | in the context of the current contract otherwise |
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+-------------------------+------+-----------------------------------------------------------------+
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| delegatecall(g, a, in, | | identical to callcode but also keep ``caller`` |
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| insize, out, outsize) | | and ``callvalue`` |
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+-------------------------+------+-----------------------------------------------------------------+
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| return(p, s) | `*` | end execution, return data mem[p..(p+s)) |
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+-------------------------+------+-----------------------------------------------------------------+
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| selfdestruct(a) | `*` | end execution, destroy current contract and send funds to a |
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+-------------------------+------+-----------------------------------------------------------------+
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| log0(p, s) | `-` | log without topics and data mem[p..(p+s)) |
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+-------------------------+------+-----------------------------------------------------------------+
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| log1(p, s, t1) | `-` | log with topic t1 and data mem[p..(p+s)) |
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+-------------------------+------+-----------------------------------------------------------------+
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| log2(p, s, t1, t2) | `-` | log with topics t1, t2 and data mem[p..(p+s)) |
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+-------------------------+------+-----------------------------------------------------------------+
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| log3(p, s, t1, t2, t3) | `-` | log with topics t1, t2, t3 and data mem[p..(p+s)) |
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+-------------------------+------+-----------------------------------------------------------------+
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| log4(p, s, t1, t2, t3, | `-` | log with topics t1, t2, t3, t4 and data mem[p..(p+s)) |
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| t4) | | |
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+-------------------------+------+-----------------------------------------------------------------+
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| origin | | transaction sender |
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+-------------------------+------+-----------------------------------------------------------------+
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| gasprice | | gas price of the transaction |
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+-------------------------+------+-----------------------------------------------------------------+
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| blockhash(b) | | hash of block nr b - only for last 256 blocks excluding current |
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+-------------------------+------+-----------------------------------------------------------------+
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| coinbase | | current mining beneficiary |
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+-------------------------+------+-----------------------------------------------------------------+
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| timestamp | | timestamp of the current block in seconds since the epoch |
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+-------------------------+------+-----------------------------------------------------------------+
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| number | | current block number |
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+-------------------------+------+-----------------------------------------------------------------+
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| difficulty | | difficulty of the current block |
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+-------------------------+------+-----------------------------------------------------------------+
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| gaslimit | | block gas limit of the current block |
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+-------------------------+------+-----------------------------------------------------------------+
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Literals
|
||||
--------
|
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|
||||
You can use integer constants by typing them in decimal or hexadecimal notation and an
|
||||
appropriate ``PUSHi`` instruction will automatically be generated. The following creates code
|
||||
to add 2 and 3 resulting in 5 and then computes the bitwise and with the string "abc".
|
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Strings are stored left-aligned and cannot be longer than 32 bytes.
|
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.. code::
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assembly { 2 3 add "abc" and }
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Functional Style
|
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-----------------
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You can type opcode after opcode in the same way they will end up in bytecode. For example
|
||||
adding ``3`` to the contents in memory at position ``0x80`` would be
|
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.. code::
|
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|
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3 0x80 mload add 0x80 mstore
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|
||||
As it is often hard to see what the actual arguments for certain opcodes are,
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Solidity inline assembly also provides a "functional style" notation where the same code
|
||||
would be written as follows
|
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||||
.. code::
|
||||
|
||||
mstore(0x80, add(mload(0x80), 3))
|
||||
|
||||
Functional style and instructional style can be mixed, but any opcode inside a
|
||||
functional style expression has to return exactly one stack slot (most of the opcodes do).
|
||||
|
||||
Note that the order of arguments is reversed in functional-style as opposed to the instruction-style
|
||||
way. If you use functional-style, the first argument will end up on the stack top.
|
||||
|
||||
|
||||
Access to External Variables and Functions
|
||||
------------------------------------------
|
||||
|
||||
Solidity variables and other identifiers can be accessed by simply using their name.
|
||||
For storage and memory variables, this will push the address and not the value onto the
|
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stack. Also note that non-struct and non-array storage variable addresses occupy two slots
|
||||
on the stack: One for the address and one for the byte offset inside the storage slot.
|
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In assignments (see below), we can even use local Solidity variables to assign to.
|
||||
|
||||
Functions external to inline assembly can also be accessed: The assembly will
|
||||
push their entry label (with virtual function resolution applied). The calling semantics
|
||||
in solidity are:
|
||||
|
||||
- the caller pushes return label, arg1, arg2, ..., argn
|
||||
- the call returns with ret1, ret2, ..., retn
|
||||
|
||||
This feature is still a bit cumbersome to use, because the stack offset essentially
|
||||
changes during the call, and thus references to local variables will be wrong.
|
||||
It is planned that the stack height changes can be specified in inline assembly.
|
||||
|
||||
.. code::
|
||||
|
||||
contract C {
|
||||
uint b;
|
||||
function f(uint x) returns (uint r) {
|
||||
assembly {
|
||||
b pop // remove the offset, we know it is zero
|
||||
sload
|
||||
x
|
||||
mul
|
||||
=: r // assign to return variable r
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
Labels
|
||||
------
|
||||
|
||||
Another problem in EVM assembly is that ``jump`` and ``jumpi`` use absolute addresses
|
||||
which can change easily. Solidity inline assembly provides labels to make the use of
|
||||
jumps easier. The following code computes an element in the Fibonacci series.
|
||||
|
||||
.. code::
|
||||
|
||||
{
|
||||
let n := calldataload(4)
|
||||
let a := 1
|
||||
let b := a
|
||||
loop:
|
||||
jumpi(loopend, eq(n, 0))
|
||||
a add swap1
|
||||
n := sub(n, 1)
|
||||
jump(loop)
|
||||
loopend:
|
||||
mstore(0, a)
|
||||
return(0, 0x20)
|
||||
}
|
||||
|
||||
Please note that automatically accessing stack variables can only work if the
|
||||
assembler knows the current stack height. This fails to work if the jump source
|
||||
and target have different stack heights. It is still fine to use such jumps, but
|
||||
you should just not access any stack variables (even assembly variables) in that case.
|
||||
|
||||
Furthermore, the stack height analyser goes through the code opcode by opcode
|
||||
(and not according to control flow), so in the following case, the assembler
|
||||
will have a wrong impression about the stack height at label ``two``:
|
||||
|
||||
.. code::
|
||||
|
||||
{
|
||||
jump(two)
|
||||
one:
|
||||
// Here the stack height is 1 (because we pushed 7),
|
||||
// but the assembler thinks it is 0 because it reads
|
||||
// from top to bottom.
|
||||
// Accessing stack variables here will lead to errors.
|
||||
jump(three)
|
||||
two:
|
||||
7 // push something onto the stack
|
||||
jump(one)
|
||||
three:
|
||||
}
|
||||
|
||||
|
||||
Declaring Assembly-Local Variables
|
||||
----------------------------------
|
||||
|
||||
You can use the ``let`` keyword to declare variables that are only visible in
|
||||
inline assembly and actually only in the current ``{...}``-block. What happens
|
||||
is that the ``let`` instruction will create a new stack slot that is reserved
|
||||
for the variable and automatically removed again when the end of the block
|
||||
is reached. You need to provide an initial value for the variable which can
|
||||
be just ``0``, but it can also be a complex functional-style expression.
|
||||
|
||||
.. code::
|
||||
|
||||
contract C {
|
||||
function f(uint x) returns (uint b) {
|
||||
assembly {
|
||||
let v := add(x, 1)
|
||||
mstore(0x80, v)
|
||||
{
|
||||
let y := add(sload(v), 1)
|
||||
b := y
|
||||
} // y is "deallocated" here
|
||||
b := add(b, v)
|
||||
} // v is "deallocated" here
|
||||
}
|
||||
}
|
||||
|
||||
|
||||
Assignments
|
||||
-----------
|
||||
|
||||
Assignments are possible to assembly-local variables and to function-local
|
||||
variables. Take care that when you assign to variables that point to
|
||||
memory or storage, you will only change the pointer and not the data.
|
||||
|
||||
There are two kinds of assignments: functional-style and instruction-style.
|
||||
For functional-style assignments (``variable := value``), you need to provide a value in a
|
||||
functional-style expression that results in exactly one stack value
|
||||
and for instruction-style (``=: variable``), the value is just taken from the stack top.
|
||||
For both ways, the colon points to the name of the variable. The assignment
|
||||
is performed by replacing the variable's value on the stack by the new value.
|
||||
|
||||
.. code::
|
||||
|
||||
assembly {
|
||||
let v := 0 // functional-style assignment as part of variable declaration
|
||||
let g := add(v, 2)
|
||||
sload(10)
|
||||
=: v // instruction style assignment, puts the result of sload(10) into v
|
||||
}
|
||||
|
||||
Switch
|
||||
------
|
||||
|
||||
You can use a switch statement as a very basic version of "if/else".
|
||||
It takes the value of an expression and compares it to several constants.
|
||||
The branch corresponding to the matching constant is taken. Contrary to the
|
||||
error-prone behaviour of some programming languages, control flow does
|
||||
not continue from one case to the next. There can be a fallback or default
|
||||
case called ``default``.
|
||||
|
||||
.. code::
|
||||
|
||||
assembly {
|
||||
let x := 0
|
||||
switch calldataload(4)
|
||||
case 0: {
|
||||
x := calldataload(0x24)
|
||||
}
|
||||
default: {
|
||||
x := calldataload(0x44)
|
||||
}
|
||||
sstore(0, div(x, 2))
|
||||
}
|
||||
|
||||
The list of cases does not require curly braces, but the body of a
|
||||
case does require them.
|
||||
|
||||
Loops
|
||||
-----
|
||||
|
||||
Assembly supports a simple for-style loop. For-style loops have
|
||||
a header containing an initializing part, a condition and a post-iteration
|
||||
part. The condition has to be a functional-style expression, while
|
||||
the other two can also be blocks. If the initializing part is a block that
|
||||
declares any variables, the scope of these variables is extended into the
|
||||
body (including the condition and the post-iteration part).
|
||||
|
||||
The following example computes the sum of an area in memory.
|
||||
|
||||
.. code::
|
||||
|
||||
assembly {
|
||||
let x := 0
|
||||
for { let i := 0 } lt(i, 0x100) { i := add(i, 0x20) } {
|
||||
x := add(x, mload(i))
|
||||
}
|
||||
}
|
||||
|
||||
Functions
|
||||
---------
|
||||
|
||||
Assembly allows the definition of low-level functions. These take their
|
||||
arguments (and a return PC) from the stack and also put the results onto the
|
||||
stack. Calling a function looks the same way as executing a functional-style
|
||||
opcode.
|
||||
|
||||
Functions can be defined anywhere and are visible in the block they are
|
||||
declared in. Inside a function, you cannot access local variables
|
||||
defined outside of that function. There is no explicit ``return``
|
||||
statement.
|
||||
|
||||
If you call a function that returns multiple values, you have to assign
|
||||
them to a tuple using ``(a, b) := f(x)`` or ``let (a, b) := f(x)``.
|
||||
|
||||
The following example implements the power function by square-and-multiply.
|
||||
|
||||
.. code::
|
||||
|
||||
assembly {
|
||||
function power(base, exponent) -> (result) {
|
||||
switch exponent
|
||||
0: { result := 1 }
|
||||
1: { result := base }
|
||||
default: {
|
||||
result := power(mul(base, base), div(exponent, 2))
|
||||
switch mod(exponent, 2)
|
||||
1: { result := mul(base, result) }
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
Things to Avoid
|
||||
---------------
|
||||
|
||||
Inline assembly might have a quite high-level look, but it actually is extremely
|
||||
low-level. Function calls, loops and switches are converted by simple
|
||||
rewriting rules and after that, the only thing the assembler does for you is re-arranging
|
||||
functional-style opcodes, managing jump labels, counting stack height for
|
||||
variable access and removing stack slots for assembly-local variables when the end
|
||||
of their block is reached. Especially for those two last cases, it is important
|
||||
to know that the assembler only counts stack height from top to bottom, not
|
||||
necessarily following control flow. Furthermore, operations like swap will only
|
||||
swap the contents of the stack but not the location of variables.
|
||||
|
||||
Conventions in Solidity
|
||||
-----------------------
|
||||
|
||||
In contrast to EVM assembly, Solidity knows types which are narrower than 256 bits,
|
||||
e.g. ``uint24``. In order to make them more efficient, most arithmetic operations just
|
||||
treat them as 256 bit numbers and the higher-order bits are only cleaned at the
|
||||
point where it is necessary, i.e. just shortly before they are written to memory
|
||||
or before comparisons are performed. This means that if you access such a variable
|
||||
from within inline assembly, you might have to manually clean the higher order bits
|
||||
first.
|
||||
|
||||
Solidity manages memory in a very simple way: There is a "free memory pointer"
|
||||
at position ``0x40`` in memory. If you want to allocate memory, just use the memory
|
||||
from that point on and update the pointer accordingly.
|
||||
|
||||
Elements in memory arrays in Solidity always occupy multiples of 32 bytes (yes, this is
|
||||
even true for ``byte[]``, but not for ``bytes`` and ``string``). Multi-dimensional memory
|
||||
arrays are pointers to memory arrays. The length of a dynamic array is stored at the
|
||||
first slot of the array and then only the array elements follow.
|
||||
|
||||
.. warning::
|
||||
Statically-sized memory arrays do not have a length field, but it will be added soon
|
||||
to allow better convertibility between statically- and dynamically-sized arrays, so
|
||||
please do not rely on that.
|
||||
|
||||
|
||||
Standalone Assembly
|
||||
===================
|
||||
|
||||
The assembly language described as inline assembly above can also be used
|
||||
standalone and in fact, the plan is to use it as an intermediate language
|
||||
for the Solidity compiler. In this form, it tries to achieve several goals:
|
||||
|
||||
1. Programs written in it should be readable, even if the code is generated by a compiler from Solidity.
|
||||
2. The translation from assembly to bytecode should contain as few "surprises" as possible.
|
||||
3. Control flow should be easy to detect to help in formal verification and optimization.
|
||||
|
||||
In order to achieve the first and last goal, assembly provides high-level constructs
|
||||
like ``for`` loops, ``switch`` statements and function calls. It should be possible
|
||||
to write assembly programs that do not make use of explicit ``SWAP``, ``DUP``,
|
||||
``JUMP`` and ``JUMPI`` statements, because the first two obfuscate the data flow
|
||||
and the last two obfuscate control flow. Furthermore, functional statements of
|
||||
the form ``mul(add(x, y), 7)`` are preferred over pure opcode statements like
|
||||
``7 y x add mul`` because in the first form, it is much easier to see which
|
||||
operand is used for which opcode.
|
||||
|
||||
The second goal is achieved by introducing a desugaring phase that only removes
|
||||
the higher level constructs in a very regular way and still allows inspecting
|
||||
the generated low-level assembly code. The only non-local operation performed
|
||||
by the assembler is name lookup of user-defined identifiers (functions, variables, ...),
|
||||
which follow very simple and regular scoping rules and cleanup of local variables from the stack.
|
||||
|
||||
Scoping: An identifier that is declared (label, variable, function, assembly)
|
||||
is only visible in the block where it was declared (including nested blocks
|
||||
inside the current block). It is not legal to access local variables across
|
||||
function borders, even if they would be in scope. Shadowing is allowed, but
|
||||
two identifiers with the same name cannot be declared in the same block.
|
||||
Local variables cannot be accessed before they were declared, but labels,
|
||||
functions and assemblies can. Assemblies are special blocks that are used
|
||||
for e.g. returning runtime code or creating contracts. No identifier from an
|
||||
outer assembly is visible in a sub-assembly.
|
||||
|
||||
If control flow passes over the end of a block, pop instructions are inserted
|
||||
that match the number of local variables declared in that block, unless the
|
||||
``}`` is directly preceded by an opcode that does not have a continuing control
|
||||
flow path. Whenever a local variable is referenced, the code generator needs
|
||||
to know its current relative position in the stack and thus it needs to
|
||||
keep track of the current so-called stack height.
|
||||
At the end of a block, this implicit stack height is always reduced by the number
|
||||
of local variables whether ther is a continuing control flow or not.
|
||||
|
||||
This means that the stack height before and after the block should be the same.
|
||||
If this is not the case, a warning is issued,
|
||||
unless the last instruction in the block did not have a continuing control flow path.
|
||||
|
||||
Why do we use higher-level constructs like ``switch``, ``for`` and functions:
|
||||
|
||||
Using ``switch``, ``for`` and functions, it should be possible to write
|
||||
complex code without using ``jump`` or ``jumpi`` manually. This makes it much
|
||||
easier to analyze the control flow, which allows for improved formal
|
||||
verification and optimization.
|
||||
|
||||
Furthermore, if manual jumps are allowed, computing the stack height is rather complicated.
|
||||
The position of all local variables on the stack needs to be known, otherwise
|
||||
neither references to local variables nor removing local variables automatically
|
||||
from the stack at the end of a block will work properly. Because of that,
|
||||
every label that is preceded by an instruction that ends or diverts control flow
|
||||
should be annotated with the current stack layout. This annotation is performed
|
||||
automatically during the desugaring phase.
|
||||
|
||||
Example:
|
||||
|
||||
We will follow an example compilation from Solidity to desugared assembly.
|
||||
We consider the runtime bytecode of the following Solidity program::
|
||||
|
||||
contract C {
|
||||
function f(uint x) returns (uint y) {
|
||||
y = 1;
|
||||
for (uint i = 0; i < x; i++)
|
||||
y = 2 * y;
|
||||
}
|
||||
}
|
||||
|
||||
The following assembly will be generated::
|
||||
|
||||
{
|
||||
mstore(0x40, 0x60) // store the "free memory pointer"
|
||||
// function dispatcher
|
||||
switch div(calldataload(0), exp(2, 226))
|
||||
case 0xb3de648b: {
|
||||
let (r) = f(calldataload(4))
|
||||
let ret := $allocate(0x20)
|
||||
mstore(ret, r)
|
||||
return(ret, 0x20)
|
||||
}
|
||||
default: { jump(invalidJumpLabel) }
|
||||
// memory allocator
|
||||
function $allocate(size) -> (pos) {
|
||||
pos := mload(0x40)
|
||||
mstore(0x40, add(pos, size))
|
||||
}
|
||||
// the contract function
|
||||
function f(x) -> (y) {
|
||||
y := 1
|
||||
for { let i := 0 } lt(i, x) { i := add(i, 1) } {
|
||||
y := mul(2, y)
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
After the desugaring phase it looks as follows::
|
||||
|
||||
{
|
||||
mstore(0x40, 0x60)
|
||||
{
|
||||
let $0 := div(calldataload(0), exp(2, 226))
|
||||
jumpi($case1, eq($0, 0xb3de648b))
|
||||
jump($caseDefault)
|
||||
$case1:
|
||||
{
|
||||
// the function call - we put return label and arguments on the stack
|
||||
$ret1 calldataload(4) jump($fun_f)
|
||||
$ret1 [r]: // a label with a [...]-annotation resets the stack height
|
||||
// to "current block + number of local variables". It also
|
||||
// introduces a variable, r:
|
||||
// r is at top of stack, $0 is below (from enclosing block)
|
||||
$ret2 0x20 jump($fun_allocate)
|
||||
$ret2 [ret]: // stack here: $0, r, ret (top)
|
||||
mstore(ret, r)
|
||||
return(ret, 0x20)
|
||||
// although it is useless, the jump is automatically inserted,
|
||||
// since the desugaring process does not analyze control-flow
|
||||
jump($endswitch)
|
||||
}
|
||||
$caseDefault:
|
||||
{
|
||||
jump(invalidJumpLabel)
|
||||
jump($endswitch)
|
||||
}
|
||||
$endswitch:
|
||||
}
|
||||
jump($afterFunction)
|
||||
$fun_allocate:
|
||||
{
|
||||
$start[$retpos, size]:
|
||||
// output variables live in the same scope as the arguments.
|
||||
let pos := 0
|
||||
{
|
||||
pos := mload(0x40)
|
||||
mstore(0x40, add(pos, size))
|
||||
}
|
||||
swap1 pop swap1 jump
|
||||
}
|
||||
$fun_f:
|
||||
{
|
||||
start [$retpos, x]:
|
||||
let y := 0
|
||||
{
|
||||
let i := 0
|
||||
$for_begin:
|
||||
jumpi($for_end, iszero(lt(i, x)))
|
||||
{
|
||||
y := mul(2, y)
|
||||
}
|
||||
$for_continue:
|
||||
{ i := add(i, 1) }
|
||||
jump($for_begin)
|
||||
$for_end:
|
||||
} // Here, a pop instruction is inserted for i
|
||||
swap1 pop swap1 jump
|
||||
}
|
||||
$afterFunction:
|
||||
stop
|
||||
}
|
||||
|
||||
|
||||
Assembly happens in four stages:
|
||||
|
||||
1. Parsing
|
||||
2. Desugaring (removes switch, for and functions)
|
||||
3. Opcode stream generation
|
||||
4. Bytecode generation
|
||||
|
||||
We will specify steps one to three in a pseudo-formal way. More formal
|
||||
specifications will follow.
|
||||
|
||||
|
||||
Parsing / Grammar
|
||||
-----------------
|
||||
|
||||
The tasks of the parser are the following:
|
||||
|
||||
- Turn the byte stream into a token stream, discarding C++-style comments
|
||||
(a special comment exists for source references, but we will not explain it here).
|
||||
- Turn the token stream into an AST according to the grammar below
|
||||
- Register identifiers with the block they are defined in (annotation to the
|
||||
AST node) and note from which point on, variables can be accessed.
|
||||
|
||||
The assembly lexer follows the one defined by Solidity itself.
|
||||
|
||||
Whitespace is used to delimit tokens and it consists of the characters
|
||||
Space, Tab and Linefeed. Comments are regular JavaScript/C++ comments and
|
||||
are interpreted in the same way as Whitespace.
|
||||
|
||||
Grammar::
|
||||
|
||||
AssemblyBlock = '{' AssemblyItem* '}'
|
||||
AssemblyItem =
|
||||
Identifier |
|
||||
AssemblyBlock |
|
||||
FunctionalAssemblyExpression |
|
||||
AssemblyLocalDefinition |
|
||||
FunctionalAssemblyAssignment |
|
||||
AssemblyAssignment |
|
||||
LabelDefinition |
|
||||
AssemblySwitch |
|
||||
AssemblyFunctionDefinition |
|
||||
AssemblyFor |
|
||||
'break' | 'continue' |
|
||||
SubAssembly | 'dataSize' '(' Identifier ')' |
|
||||
LinkerSymbol |
|
||||
'errorLabel' | 'bytecodeSize' |
|
||||
NumberLiteral | StringLiteral | HexLiteral
|
||||
Identifier = [a-zA-Z_$] [a-zA-Z_0-9]*
|
||||
FunctionalAssemblyExpression = Identifier '(' ( AssemblyItem ( ',' AssemblyItem )* )? ')'
|
||||
AssemblyLocalDefinition = 'let' IdentifierOrList ':=' FunctionalAssemblyExpression
|
||||
FunctionalAssemblyAssignment = IdentifierOrList ':=' FunctionalAssemblyExpression
|
||||
IdentifierOrList = Identifier | '(' IdentifierList ')'
|
||||
IdentifierList = Identifier ( ',' Identifier)*
|
||||
AssemblyAssignment = '=:' Identifier
|
||||
LabelDefinition = Identifier ( '[' ( IdentifierList | NumberLiteral ) ']' )? ':'
|
||||
AssemblySwitch = 'switch' FunctionalAssemblyExpression AssemblyCase*
|
||||
( 'default' ':' AssemblyBlock )?
|
||||
AssemblyCase = 'case' FunctionalAssemblyExpression ':' AssemblyBlock
|
||||
AssemblyFunctionDefinition = 'function' Identifier '(' IdentifierList? ')'
|
||||
( '->' '(' IdentifierList ')' )? AssemblyBlock
|
||||
AssemblyFor = 'for' ( AssemblyBlock | FunctionalAssemblyExpression)
|
||||
FunctionalAssemblyExpression ( AssemblyBlock | FunctionalAssemblyExpression) AssemblyBlock
|
||||
SubAssembly = 'assembly' Identifier AssemblyBlock
|
||||
LinkerSymbol = 'linkerSymbol' '(' StringLiteral ')'
|
||||
NumberLiteral = HexNumber | DecimalNumber
|
||||
HexLiteral = 'hex' ('"' ([0-9a-fA-F]{2})* '"' | '\'' ([0-9a-fA-F]{2})* '\'')
|
||||
StringLiteral = '"' ([^"\r\n\\] | '\\' .)* '"'
|
||||
HexNumber = '0x' [0-9a-fA-F]+
|
||||
DecimalNumber = [0-9]+
|
||||
|
||||
|
||||
Desugaring
|
||||
----------
|
||||
|
||||
An AST transformation removes for, switch and function constructs. The result
|
||||
is still parseable by the same parser, but it will not use certain constructs.
|
||||
If jumpdests are added that are only jumped to and not continued at, information
|
||||
about the stack content is added, unless no local variables of outer scopes are
|
||||
accessed or the stack height is the same as for the previous instruction.
|
||||
|
||||
Pseudocode::
|
||||
|
||||
desugar item: AST -> AST =
|
||||
match item {
|
||||
AssemblyFunctionDefinition('function' name '(' arg1, ..., argn ')' '->' ( '(' ret1, ..., retm ')' body) ->
|
||||
<name>:
|
||||
{
|
||||
$<name>_start [$retPC, $argn, ..., arg1]:
|
||||
let ret1 := 0 ... let retm := 0
|
||||
{ desugar(body) }
|
||||
swap and pop items so that only ret1, ... retn, $retPC are left on the stack
|
||||
jump
|
||||
}
|
||||
AssemblyFor('for' { init } condition post body) ->
|
||||
{
|
||||
init // cannot be its own block because we want variable scope to extend into the body
|
||||
// find I such that there are no labels $forI_*
|
||||
$forI_begin:
|
||||
jumpi($forI_end, iszero(condition))
|
||||
{ body }
|
||||
$forI_continue:
|
||||
{ post }
|
||||
jump($forI_begin)
|
||||
$forI_end:
|
||||
}
|
||||
'break' ->
|
||||
{
|
||||
// find nearest enclosing scope with label $forI_end
|
||||
pop all local variables that are defined at the current point
|
||||
but not at $forI_end
|
||||
jump($forI_end)
|
||||
}
|
||||
'continue' ->
|
||||
{
|
||||
// find nearest enclosing scope with label $forI_continue
|
||||
pop all local variables that are defined at the current point
|
||||
but not at $forI_continue
|
||||
jump($forI_continue)
|
||||
}
|
||||
AssemblySwitch(switch condition cases ( default: defaultBlock )? ) ->
|
||||
{
|
||||
// find I such that there is no $switchI* label or variable
|
||||
let $switchI_value := condition
|
||||
for each of cases match {
|
||||
case val: -> jumpi($switchI_caseJ, eq($switchI_value, val))
|
||||
}
|
||||
if default block present: ->
|
||||
{ defaultBlock jump($switchI_end) }
|
||||
for each of cases match {
|
||||
case val: { body } -> $switchI_caseJ: { body jump($switchI_end) }
|
||||
}
|
||||
$switchI_end:
|
||||
}
|
||||
FunctionalAssemblyExpression( identifier(arg1, arg2, ..., argn) ) ->
|
||||
{
|
||||
if identifier is function <name> with n args and m ret values ->
|
||||
{
|
||||
// find I such that $funcallI_* does not exist
|
||||
$funcallI_return argn ... arg2 arg1 jump(<name>)
|
||||
if the current context is `let (id1, ..., idm) := f(...)` ->
|
||||
$funcallI_return [id1, ..., idm]:
|
||||
else ->
|
||||
$funcallI_return[m - n - 1]:
|
||||
turn the functional expression that leads to the function call
|
||||
into a statement stream
|
||||
}
|
||||
else -> desugar(children of node)
|
||||
}
|
||||
default node ->
|
||||
desugar(children of node)
|
||||
}
|
||||
|
||||
Opcode Stream Generation
|
||||
------------------------
|
||||
|
||||
During opcode stream generation, we keep track of the current stack height,
|
||||
so that accessing stack variables by name is possible.
|
||||
|
||||
Pseudocode::
|
||||
|
||||
codegen item: AST -> opcode_stream =
|
||||
match item {
|
||||
AssemblyBlock({ items }) ->
|
||||
join(codegen(item) for item in items)
|
||||
if last generated opcode has continuing control flow:
|
||||
POP for all local variables registered at the block (including variables
|
||||
introduced by labels)
|
||||
warn if the stack height at this point is not the same as at the start of the block
|
||||
Identifier(id) ->
|
||||
lookup id in the syntactic stack of blocks
|
||||
match type of id
|
||||
Local Variable ->
|
||||
DUPi where i = 1 + stack_height - stack_height_of_identifier(id)
|
||||
Label ->
|
||||
// reference to be resolved during bytecode generation
|
||||
PUSH<bytecode position of label>
|
||||
SubAssembly ->
|
||||
PUSH<bytecode position of subassembly data>
|
||||
FunctionalAssemblyExpression(id ( arguments ) ) ->
|
||||
join(codegen(arg) for arg in arguments.reversed())
|
||||
id (which has to be an opcode, might be a function name later)
|
||||
AssemblyLocalDefinition(let (id1, ..., idn) := expr) ->
|
||||
register identifiers id1, ..., idn as locals in current block at current stack height
|
||||
codegen(expr) - assert that expr returns n items to the stack
|
||||
FunctionalAssemblyAssignment((id1, ..., idn) := expr) ->
|
||||
lookup id1, ..., idn in the syntactic stack of blocks, assert that they are variables
|
||||
codegen(expr)
|
||||
for j = n, ..., i:
|
||||
SWAPi where i = 1 + stack_height - stack_height_of_identifier(idj)
|
||||
POP
|
||||
AssemblyAssignment(=: id) ->
|
||||
look up id in the syntactic stack of blocks, assert that it is a variable
|
||||
SWAPi where i = 1 + stack_height - stack_height_of_identifier(id)
|
||||
POP
|
||||
LabelDefinition(name [id1, ..., idn] :) ->
|
||||
JUMPDEST
|
||||
// register new variables id1, ..., idn and set the stack height to
|
||||
// stack_height_at_block_start + number_of_local_variables
|
||||
LabelDefinition(name [number] :) ->
|
||||
JUMPDEST
|
||||
// adjust stack height by +number (can be negative)
|
||||
NumberLiteral(num) ->
|
||||
PUSH<num interpreted as decimal and right-aligned>
|
||||
HexLiteral(lit) ->
|
||||
PUSH32<lit interpreted as hex and left-aligned>
|
||||
StringLiteral(lit) ->
|
||||
PUSH32<lit utf-8 encoded and left-aligned>
|
||||
SubAssembly(assembly <name> block) ->
|
||||
append codegen(block) at the end of the code
|
||||
dataSize(<name>) ->
|
||||
assert that <name> is a subassembly ->
|
||||
PUSH32<size of code generated from subassembly <name>>
|
||||
linkerSymbol(<lit>) ->
|
||||
PUSH32<zeros> and append position to linker table
|
||||
}
|
@ -16,4 +16,5 @@ If something is missing here, please contact us on
|
||||
units-and-global-variables.rst
|
||||
control-structures.rst
|
||||
contracts.rst
|
||||
assembly.rst
|
||||
miscellaneous.rst
|
||||
|
@ -117,69 +117,36 @@ string Assembly::locationFromSources(StringMap const& _sourceCodes, SourceLocati
|
||||
|
||||
ostream& Assembly::streamAsm(ostream& _out, string const& _prefix, StringMap const& _sourceCodes) const
|
||||
{
|
||||
_out << _prefix << ".code:" << endl;
|
||||
for (AssemblyItem const& i: m_items)
|
||||
for (size_t i = 0; i < m_items.size(); ++i)
|
||||
{
|
||||
_out << _prefix;
|
||||
switch (i.type())
|
||||
AssemblyItem const& item = m_items[i];
|
||||
if (!item.location().isEmpty() && (i == 0 || m_items[i - 1].location() != item.location()))
|
||||
{
|
||||
case Operation:
|
||||
_out << " " << instructionInfo(i.instruction()).name << "\t" << i.getJumpTypeAsString();
|
||||
break;
|
||||
case Push:
|
||||
_out << " PUSH" << dec << max<unsigned>(1, dev::bytesRequired(i.data())) << " 0x" << hex << i.data();
|
||||
break;
|
||||
case PushString:
|
||||
_out << " PUSH \"" << m_strings.at((h256)i.data()) << "\"";
|
||||
break;
|
||||
case PushTag:
|
||||
if (i.data() == 0)
|
||||
_out << " PUSH [ErrorTag]";
|
||||
else
|
||||
{
|
||||
size_t subId = i.splitForeignPushTag().first;
|
||||
if (subId == size_t(-1))
|
||||
_out << " PUSH [tag" << dec << i.splitForeignPushTag().second << "]";
|
||||
else
|
||||
_out << " PUSH [tag" << dec << subId << ":" << i.splitForeignPushTag().second << "]";
|
||||
}
|
||||
break;
|
||||
case PushSub:
|
||||
_out << " PUSH [$" << size_t(i.data()) << "]";
|
||||
break;
|
||||
case PushSubSize:
|
||||
_out << " PUSH #[$" << size_t(i.data()) << "]";
|
||||
break;
|
||||
case PushProgramSize:
|
||||
_out << " PUSHSIZE";
|
||||
break;
|
||||
case PushLibraryAddress:
|
||||
_out << " PUSHLIB \"" << m_libraries.at(h256(i.data())) << "\"";
|
||||
break;
|
||||
case Tag:
|
||||
_out << "tag" << dec << i.data() << ": " << endl << _prefix << " JUMPDEST";
|
||||
break;
|
||||
case PushData:
|
||||
_out << " PUSH [" << hex << (unsigned)i.data() << "]";
|
||||
break;
|
||||
default:
|
||||
BOOST_THROW_EXCEPTION(InvalidOpcode());
|
||||
_out << _prefix << " /*";
|
||||
if (item.location().sourceName)
|
||||
_out << " \"" + *item.location().sourceName + "\"";
|
||||
if (!item.location().isEmpty())
|
||||
_out << ":" << to_string(item.location().start) + ":" + to_string(item.location().end);
|
||||
_out << " */" << endl;
|
||||
}
|
||||
_out << "\t\t" << locationFromSources(_sourceCodes, i.location()) << endl;
|
||||
_out << _prefix << (item.type() == Tag ? "" : " ") << item.toAssemblyText() << endl;
|
||||
}
|
||||
|
||||
if (!m_data.empty() || !m_subs.empty())
|
||||
{
|
||||
_out << _prefix << ".data:" << endl;
|
||||
_out << _prefix << "stop" << endl;
|
||||
Json::Value data;
|
||||
for (auto const& i: m_data)
|
||||
if (u256(i.first) >= m_subs.size())
|
||||
_out << _prefix << " " << hex << (unsigned)(u256)i.first << ": " << dev::toHex(i.second) << endl;
|
||||
assertThrow(u256(i.first) < m_subs.size(), AssemblyException, "Data not yet implemented.");
|
||||
|
||||
for (size_t i = 0; i < m_subs.size(); ++i)
|
||||
{
|
||||
_out << _prefix << " " << hex << i << ": " << endl;
|
||||
m_subs[i]->stream(_out, _prefix + " ", _sourceCodes);
|
||||
_out << endl << _prefix << "sub_" << i << ": assembly {\n";
|
||||
m_subs[i]->streamAsm(_out, _prefix + " ", _sourceCodes);
|
||||
_out << _prefix << "}" << endl;
|
||||
}
|
||||
}
|
||||
|
||||
return _out;
|
||||
}
|
||||
|
||||
|
@ -20,6 +20,7 @@
|
||||
*/
|
||||
|
||||
#include "AssemblyItem.h"
|
||||
#include <libevmasm/SemanticInformation.h>
|
||||
#include <fstream>
|
||||
|
||||
using namespace std;
|
||||
@ -97,6 +98,28 @@ int AssemblyItem::deposit() const
|
||||
return 0;
|
||||
}
|
||||
|
||||
bool AssemblyItem::canBeFunctional() const
|
||||
{
|
||||
switch (m_type)
|
||||
{
|
||||
case Operation:
|
||||
return !SemanticInformation::isDupInstruction(*this) && !SemanticInformation::isSwapInstruction(*this);
|
||||
case Push:
|
||||
case PushString:
|
||||
case PushTag:
|
||||
case PushData:
|
||||
case PushSub:
|
||||
case PushSubSize:
|
||||
case PushProgramSize:
|
||||
case PushLibraryAddress:
|
||||
return true;
|
||||
case Tag:
|
||||
return false;
|
||||
default:;
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
string AssemblyItem::getJumpTypeAsString() const
|
||||
{
|
||||
switch (m_jumpType)
|
||||
@ -111,6 +134,65 @@ string AssemblyItem::getJumpTypeAsString() const
|
||||
}
|
||||
}
|
||||
|
||||
string AssemblyItem::toAssemblyText() const
|
||||
{
|
||||
string text;
|
||||
switch (type())
|
||||
{
|
||||
case Operation:
|
||||
{
|
||||
assertThrow(isValidInstruction(instruction()), AssemblyException, "Invalid instruction.");
|
||||
string name = instructionInfo(instruction()).name;
|
||||
transform(name.begin(), name.end(), name.begin(), [](unsigned char _c) { return tolower(_c); });
|
||||
text = name;
|
||||
break;
|
||||
}
|
||||
case Push:
|
||||
text = toHex(toCompactBigEndian(data(), 1), 1, HexPrefix::Add);
|
||||
break;
|
||||
case PushString:
|
||||
assertThrow(false, AssemblyException, "Push string assembly output not implemented.");
|
||||
break;
|
||||
case PushTag:
|
||||
assertThrow(data() < 0x10000, AssemblyException, "Sub-assembly tags not yet implemented.");
|
||||
text = string("tag_") + to_string(size_t(data()));
|
||||
break;
|
||||
case Tag:
|
||||
assertThrow(data() < 0x10000, AssemblyException, "Sub-assembly tags not yet implemented.");
|
||||
text = string("tag_") + to_string(size_t(data())) + ":";
|
||||
break;
|
||||
case PushData:
|
||||
assertThrow(false, AssemblyException, "Push data not implemented.");
|
||||
break;
|
||||
case PushSub:
|
||||
text = string("dataOffset(sub_") + to_string(size_t(data())) + ")";
|
||||
break;
|
||||
case PushSubSize:
|
||||
text = string("dataSize(sub_") + to_string(size_t(data())) + ")";
|
||||
break;
|
||||
case PushProgramSize:
|
||||
text = string("bytecodeSize");
|
||||
break;
|
||||
case PushLibraryAddress:
|
||||
text = string("linkerSymbol(\"") + toHex(data()) + string("\")");
|
||||
break;
|
||||
case UndefinedItem:
|
||||
assertThrow(false, AssemblyException, "Invalid assembly item.");
|
||||
break;
|
||||
default:
|
||||
BOOST_THROW_EXCEPTION(InvalidOpcode());
|
||||
}
|
||||
if (m_jumpType == JumpType::IntoFunction || m_jumpType == JumpType::OutOfFunction)
|
||||
{
|
||||
text += "\t//";
|
||||
if (m_jumpType == JumpType::IntoFunction)
|
||||
text += " in";
|
||||
else
|
||||
text += " out";
|
||||
}
|
||||
return text;
|
||||
}
|
||||
|
||||
ostream& dev::eth::operator<<(ostream& _out, AssemblyItem const& _item)
|
||||
{
|
||||
switch (_item.type())
|
||||
|
@ -97,6 +97,9 @@ public:
|
||||
unsigned bytesRequired(unsigned _addressLength) const;
|
||||
int deposit() const;
|
||||
|
||||
/// @returns true if the assembly item can be used in a functional context.
|
||||
bool canBeFunctional() const;
|
||||
|
||||
bool match(AssemblyItem const& _i) const { return _i.m_type == UndefinedItem || (m_type == _i.m_type && (m_type != Operation || m_data == _i.m_data)); }
|
||||
void setLocation(SourceLocation const& _location) { m_location = _location; }
|
||||
SourceLocation const& location() const { return m_location; }
|
||||
@ -108,6 +111,8 @@ public:
|
||||
void setPushedValue(u256 const& _value) const { m_pushedValue = std::make_shared<u256>(_value); }
|
||||
u256 const* pushedValue() const { return m_pushedValue.get(); }
|
||||
|
||||
std::string toAssemblyText() const;
|
||||
|
||||
private:
|
||||
AssemblyItemType m_type;
|
||||
u256 m_data;
|
||||
|
Loading…
Reference in New Issue
Block a user