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Merge pull request #6738 from vedant1811/docs-6489

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Fix yul example in docs
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chriseth 2019-05-14 11:56:08 +02:00 committed by GitHub
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docs/yul.rst
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@ -47,20 +47,21 @@ if the backend changes. For a list of mandatory built-in functions, see the sect
The following example program assumes that the EVM opcodes ``mul``, ``div`` The following example program assumes that the EVM opcodes ``mul``, ``div``
and ``mod`` are available either natively or as functions and computes exponentiation. and ``mod`` are available either natively or as functions and computes exponentiation.
As per the warning above, the following code is untyped and can be compiled using ``solc --strict-assembly``.
.. code:: .. code::
{ {
function power(base:u256, exponent:u256) -> result:u256 function power(base, exponent) -> result
{ {
switch exponent switch exponent
case 0:u256 { result := 1:u256 } case 0 { result := 1 }
case 1:u256 { result := base } case 1 { result := base }
default default
{ {
result := power(mul(base, base), div(exponent, 2:u256)) result := power(mul(base, base), div(exponent, 2))
switch mod(exponent, 2:u256) switch mod(exponent, 2)
case 1:u256 { result := mul(base, result) } case 1 { result := mul(base, result) }
} }
} }
} }
@ -72,10 +73,10 @@ and ``add`` to be available.
.. code:: .. code::
{ {
function power(base:u256, exponent:u256) -> result:u256 function power(base, exponent) -> result
{ {
result := 1:u256 result := 1
for { let i := 0:u256 } lt(i, exponent) { i := add(i, 1:u256) } for { let i := 0 } lt(i, exponent) { i := add(i, 1) }
{ {
result := mul(result, base) result := mul(result, base)
} }
@ -593,15 +594,21 @@ An example Yul Object is shown below:
// are in scope without nested access. // are in scope without nested access.
object "Contract1" { object "Contract1" {
code { code {
function allocate(size) -> ptr {
ptr := mload(0x40)
if iszero(ptr) { ptr := 0x60 }
mstore(0x40, add(ptr, size))
}
// first create "runtime.Contract2" // first create "runtime.Contract2"
let size = datasize("runtime.Contract2") let size := datasize("runtime.Contract2")
let offset = allocate(size) let offset := allocate(size)
// This will turn into a memory->memory copy for eWASM and // This will turn into a memory->memory copy for eWASM and
// a codecopy for EVM // a codecopy for EVM
datacopy(offset, dataoffset("runtime.Contract2"), size) datacopy(offset, dataoffset("runtime.Contract2"), size)
// constructor parameter is a single number 0x1234 // constructor parameter is a single number 0x1234
mstore(add(offset, size), 0x1234) mstore(add(offset, size), 0x1234)
create(offset, add(size, 32)) pop(create(offset, add(size, 32), 0))
// now return the runtime object (this is // now return the runtime object (this is
// constructor code) // constructor code)
@ -617,16 +624,22 @@ An example Yul Object is shown below:
object "runtime" { object "runtime" {
code { code {
function allocate(size) -> ptr {
ptr := mload(0x40)
if iszero(ptr) { ptr := 0x60 }
mstore(0x40, add(ptr, size))
}
// runtime code // runtime code
let size = datasize("Contract2") let size := datasize("Contract2")
let offset = allocate(size) let offset := allocate(size)
// This will turn into a memory->memory copy for eWASM and // This will turn into a memory->memory copy for eWASM and
// a codecopy for EVM // a codecopy for EVM
datacopy(offset, dataoffset("Contract2"), size) datacopy(offset, dataoffset("Contract2"), size)
// constructor parameter is a single number 0x1234 // constructor parameter is a single number 0x1234
mstore(add(offset, size), 0x1234) mstore(add(offset, size), 0x1234)
create(offset, add(size, 32)) pop(create(offset, add(size, 32), 0))
} }
// Embedded object. Use case is that the outside is a factory contract, // Embedded object. Use case is that the outside is a factory contract,
@ -640,9 +653,9 @@ An example Yul Object is shown below:
code { code {
// code here ... // code here ...
} }
} }
data "Table1" hex"4123" data "Table1" hex"4123"
} }
} }
} }