Add calldata located variables. #1499
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@charles-cooper could you give this a look through? :) |
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Sure! I will have to get to it next week, though. |
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Sure! I reckon it's mostly OK, I checked it over when it wasn't 4 AM ... and it still looked good hehe |
| name=arg.name, | ||
| pos=default_arg_pos, | ||
| typ=arg.typ, | ||
| mutable=False, |
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for clarity, could set location explicitly here
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@jacqueswww this looks pretty good, I didn't see the code that copies dynamic data to memory though? Could you help point it out to me? |
jacqueswww
commented
Jul 4, 2019
| @@ -138,12 +135,29 @@ def parse_public_function(code: ast.FunctionDef, | |||
| mem_pos, _ = context.memory_allocator.increase_memory(32 * get_size_of_type(arg.typ)) | |||
| context.vars[arg.name] = VariableRecord(arg.name, mem_pos, arg.typ, False) | |||
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@charles-cooper The byte-arrays are copied into memory here.
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What I did
Fixes #1381.
This is an optimisation I am glad I finally got to make! Basically we were copying variables to memory unnecessarily, by using the calldata directly one not only gets better speed - but also ensures on the EVM level the variables are read-only (yes we had a test that actually was altering a parameter in a tuple assign).
This changes affects these these function parameter types.
Note: Turned out ByteArrays were too difficult optimise, especially when they tend to have to be packed, which one would have to just allocate them again. Also one looses out not being able to always re-use the identity / mem copy contract.
Taking some files from the examples directory:
Blind Auction -> 73 % less bytecode (!!!)
ERC20 -> 4.9 % less bytecode
ERC720 -> 6.3% less bytecode
Additionally we save runtime costs because we skip 'n full N of mstore (memory growth) on each call.
Also private calls tend to be much cheaper on average, because the in-memory context is smaller.
How I did it
Used a lot of coffee ☕
How to verify it
Check commits, play with your own contracts.
Description for the changelog
Bytecode & Runtime optimisation for function parameters.
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