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Changelog and documentation.

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chriseth 2017-06-09 15:51:26 +02:00 committed by Alex Beregszaszi
parent 0745628a73
commit 71d39755fe
2 changed files with 15 additions and 26 deletions
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1
Changelog.md
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@ -8,6 +8,7 @@ Features:
* Inline Assembly: Present proper error message when not supplying enough arguments to a functional * Inline Assembly: Present proper error message when not supplying enough arguments to a functional
instruction. instruction.
* Inline Assembly: introduce ``keccak256`` as an opcode. ``sha3`` is still a valid alias. * Inline Assembly: introduce ``keccak256`` as an opcode. ``sha3`` is still a valid alias.
* Inline Assembly: ``for`` and ``switch`` statements.
Bugfixes: Bugfixes:
* Fixed crash concerning non-callable types. * Fixed crash concerning non-callable types.

40
docs/assembly.rst
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@ -28,11 +28,8 @@ arising when writing manual assembly by the following features:
* access to external variables: ``function f(uint x) { assembly { x := sub(x, 1) } }`` * access to external variables: ``function f(uint x) { assembly { x := sub(x, 1) } }``
* labels: ``let x := 10 repeat: x := sub(x, 1) jumpi(repeat, eq(x, 0))`` * labels: ``let x := 10 repeat: x := sub(x, 1) jumpi(repeat, eq(x, 0))``
* loops: ``for { let i := 0 } lt(i, x) { i := add(i, 1) } { y := mul(2, y) }`` * loops: ``for { let i := 0 } lt(i, x) { i := add(i, 1) } { y := mul(2, y) }``
* switch statements: ``switch x case 0: { y := mul(x, 2) } default: { y := 0 }`` * switch statements: ``switch x case 0 { y := mul(x, 2) } default { y := 0 }``
* function calls: ``function f(x) -> y { switch x case 0: { y := 1 } default: { y := mul(x, f(sub(x, 1))) } }`` * function calls: ``function f(x) -> y { switch x case 0 { y := 1 } default { y := mul(x, f(sub(x, 1))) } }``
.. note::
Of the above, loops, function calls and switch statements are not yet implemented.
We now want to describe the inline assembly language in detail. We now want to describe the inline assembly language in detail.
@ -501,9 +498,6 @@ is performed by replacing the variable's value on the stack by the new value.
Switch Switch
------ ------
.. note::
Switch is not yet implemented.
You can use a switch statement as a very basic version of "if/else". 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. 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 The branch corresponding to the matching constant is taken. Contrary to the
@ -516,10 +510,10 @@ case called ``default``.
assembly { assembly {
let x := 0 let x := 0
switch calldataload(4) switch calldataload(4)
case 0: { case 0 {
x := calldataload(0x24) x := calldataload(0x24)
} }
default: { default {
x := calldataload(0x44) x := calldataload(0x44)
} }
sstore(0, div(x, 2)) sstore(0, div(x, 2))
@ -531,13 +525,10 @@ case does require them.
Loops Loops
----- -----
.. note::
Loops are not yet implemented.
Assembly supports a simple for-style loop. For-style loops have Assembly supports a simple for-style loop. For-style loops have
a header containing an initializing part, a condition and a post-iteration a header containing an initializing part, a condition and a post-iteration
part. The condition has to be a functional-style expression, while 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 the other two are blocks. If the initializing part
declares any variables, the scope of these variables is extended into the declares any variables, the scope of these variables is extended into the
body (including the condition and the post-iteration part). body (including the condition and the post-iteration part).
@ -555,9 +546,6 @@ The following example computes the sum of an area in memory.
Functions Functions
--------- ---------
.. note::
Functions are not yet implemented.
Assembly allows the definition of low-level functions. These take their 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 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 stack. Calling a function looks the same way as executing a functional-style
@ -569,7 +557,7 @@ defined outside of that function. There is no explicit ``return``
statement. statement.
If you call a function that returns multiple values, you have to assign 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)``. 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. The following example implements the power function by square-and-multiply.
@ -578,12 +566,12 @@ The following example implements the power function by square-and-multiply.
assembly { assembly {
function power(base, exponent) -> result { function power(base, exponent) -> result {
switch exponent switch exponent
0: { result := 1 } case 0 { result := 1 }
1: { result := base } case 1 { result := base }
default: { default {
result := power(mul(base, base), div(exponent, 2)) result := power(mul(base, base), div(exponent, 2))
switch mod(exponent, 2) switch mod(exponent, 2)
1: { result := mul(base, result) } case 1 { result := mul(base, result) }
} }
} }
} }
@ -703,13 +691,13 @@ The following assembly will be generated::
mstore(0x40, 0x60) // store the "free memory pointer" mstore(0x40, 0x60) // store the "free memory pointer"
// function dispatcher // function dispatcher
switch div(calldataload(0), exp(2, 226)) switch div(calldataload(0), exp(2, 226))
case 0xb3de648b: { case 0xb3de648b {
let (r) = f(calldataload(4)) let (r) = f(calldataload(4))
let ret := $allocate(0x20) let ret := $allocate(0x20)
mstore(ret, r) mstore(ret, r)
return(ret, 0x20) return(ret, 0x20)
} }
default: { revert(0, 0) } default { revert(0, 0) }
// memory allocator // memory allocator
function $allocate(size) -> pos { function $allocate(size) -> pos {
pos := mload(0x40) pos := mload(0x40)
@ -860,8 +848,8 @@ Grammar::
AssemblyAssignment = '=:' Identifier AssemblyAssignment = '=:' Identifier
LabelDefinition = Identifier ':' LabelDefinition = Identifier ':'
AssemblySwitch = 'switch' FunctionalAssemblyExpression AssemblyCase* AssemblySwitch = 'switch' FunctionalAssemblyExpression AssemblyCase*
( 'default' ':' AssemblyBlock )? ( 'default' AssemblyBlock )?
AssemblyCase = 'case' FunctionalAssemblyExpression ':' AssemblyBlock AssemblyCase = 'case' FunctionalAssemblyExpression AssemblyBlock
AssemblyFunctionDefinition = 'function' Identifier '(' IdentifierList? ')' AssemblyFunctionDefinition = 'function' Identifier '(' IdentifierList? ')'
( '->' '(' IdentifierList ')' )? AssemblyBlock ( '->' '(' IdentifierList ')' )? AssemblyBlock
AssemblyFor = 'for' ( AssemblyBlock | FunctionalAssemblyExpression) AssemblyFor = 'for' ( AssemblyBlock | FunctionalAssemblyExpression)