aboutsummaryrefslogtreecommitdiffstats
path: root/docs/assembly.rst
diff options
context:
space:
mode:
authorchriseth <chris@ethereum.org>2017-04-04 01:17:17 +0800
committerAlex Beregszaszi <alex@rtfs.hu>2017-11-22 10:45:07 +0800
commit243002e5f3e491b91f017e3ac1371ed45a716f3b (patch)
treea814339e8db2006267ee5ebcce1f2f67735f4322 /docs/assembly.rst
parent4e0723ce27b343b9dd7c423542b9261d7c48927b (diff)
downloaddexon-solidity-243002e5f3e491b91f017e3ac1371ed45a716f3b.tar.gz
dexon-solidity-243002e5f3e491b91f017e3ac1371ed45a716f3b.tar.zst
dexon-solidity-243002e5f3e491b91f017e3ac1371ed45a716f3b.zip
Describe Julia.
Diffstat (limited to 'docs/assembly.rst')
-rw-r--r--docs/assembly.rst125
1 files changed, 114 insertions, 11 deletions
diff --git a/docs/assembly.rst b/docs/assembly.rst
index f5abcdc8..ce45c55c 100644
--- a/docs/assembly.rst
+++ b/docs/assembly.rst
@@ -1,18 +1,116 @@
-#################
-Solidity Assembly
-#################
+#################################################
+Joyfully Universal Language for (Inline) Assembly
+#################################################
+
+.. _julia:
.. index:: ! assembly, ! asm, ! evmasm
-Solidity defines an assembly language that can also be used without Solidity.
-This assembly language can also be used as "inline assembly" inside Solidity
-source code. We start with describing how to use inline assembly and how it
-differs from standalone assembly and then specify assembly itself.
+Julia is an intermediate language that can compile to various different backends
+(EVM 1.0, EVM 1.5 and eWASM are planned).
+Because of that, it is designed to be as featureless as possible.
+It can already be used for "inline assembly" inside Solidity and
+future versions of the Solidity compiler will even use Julia as intermediate
+language. It should also be easy to build high-level optimizer stages for Julia.
-.. note::
- TODO: Write about how scoping rules of inline assembly are a bit different
- and the complications that arise when for example using internal functions
- of libraries. Furthermore, write about the symbols defined by the compiler.
+The core components of Julia are functions, blocks, variables, literals,
+for-loops, switch-statements, expressions and assignments to variables.
+
+Julia in itself does not even provide operators. If the EVM is targeted,
+opcodes will be available as built-in functions, but they can be reimplemented
+if the backend changes.
+
+The following example program assumes that the EVM opcodes ``mul``, ``div``
+and ``mod`` are available either natively or as functions and computes exponentiation.
+
+.. code::
+ {
+ 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) }
+ }
+ }
+ }
+
+It is also possible to implement the same function using a for-loop
+instead of recursion. Here, we need the EVM opcodes ``lt`` (less-than)
+and ``add`` to be available.
+
+.. code::
+ {
+ function power(base, exponent) -> (result)
+ {
+ result := 1
+ for { let i := 0 } lt(i, exponent) { i := add(i, 1) }
+ {
+ result := mul(result, base)
+ }
+ }
+ }
+
+Specification of Julia
+======================
+
+Grammar::
+
+ Block = '{' Statement* '}'
+ Statement =
+ Block |
+ FunctionDefinition |
+ VariableDeclaration |
+ Assignment |
+ Expression |
+ Switch |
+ ForLoop |
+ 'break' | 'continue'
+ SubAssembly
+ FunctionDefinition =
+ 'function' Identifier '(' IdentifierList? ')'
+ ( '->' '(' IdentifierList ')' )? Block
+ VariableDeclaration =
+ 'let' IdentifierOrList ':=' Expression
+ Assignment =
+ IdentifierOrList ':=' Expression
+ Expression =
+ Identifier | Literal | FunctionCall
+ Switch =
+ 'switch' Expression Case* ( 'default' ':' Block )?
+ Case =
+ 'case' Expression ':' Block
+ ForLoop =
+ 'for' Block Expression Block Block
+ SubAssembly =
+ 'assembly' Identifier Block
+ FunctionCall =
+ Identifier '(' ( AssemblyItem ( ',' AssemblyItem )* )? ')'
+ IdentifierOrList = Identifier | '(' IdentifierList ')'
+ Identifier = [a-zA-Z_$] [a-zA-Z_0-9]*
+ IdentifierList = Identifier ( ',' Identifier)*
+ Literal =
+ NumberLiteral | StringLiteral | HexLiteral
+ 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]+
+
+
+
+ | 'dataSize' '(' Identifier ')' |
+ LinkerSymbol |
+ 'bytecodeSize' |
+
+Restriction for Expression: Functions can only return single item,
+top level has to return nothing.
+Restriction for VariableDeclaration and Assignment: Number of elements left and right needs to be the same
+continue and break only in for loop
.. _inline-assembly:
@@ -41,6 +139,11 @@ We now want to describe the inline assembly language in detail.
at a low level. This discards several important safety
features of Solidity.
+.. note::
+ TODO: Write about how scoping rules of inline assembly are a bit different
+ and the complications that arise when for example using internal functions
+ of libraries. Furthermore, write about the symbols defined by the compiler.
+
Example
-------