User macros

[lightclient]

This PR introduces the following new features:

Expressions

Doing arithmetic on push data is a desirable attribute of an assembler.

push1 1+2
> 6003

push1 -1+2
> 6001

While constant expressions may improve readability, they aren't that useful. The big win is doing arithmetic on label addresses.

start:
caller
pop
end:
push1 end - start
> 33506002

Any normal operand type is available as an expression term!

push4 selector("foo()")
> 63c2985578

push4 selector("foo()") - 1
> 63c2985577

Expression Macros

Expressions significantly improve the usability of eas. Now that we have a rich format for expressing mathematical expressions, it would be great if we could reuse those expressions.

%def three()
    1+2
%end
push1 three()
> 6003

%def add_one(x)
    $x+1
%end
push1 add_one(1+1)
> 6003

%def add_one(x)
    $x+1
%end
push1 add_one(three())
> 6004

Instruction Macros

Instruction macros take things a step further. While expression macros are only valid as operands, instruction macros can output arbitrary instructions into the program. This allows users to avoid repetition in their code.

%macro selector()
    calldataload
    push1 0x28
    shr
%end
%selector()
> 3560281c

# assumes the value is already the top stack element
%macro mask_value(mask)
    push1 $mask
    and
%end
push1 0b11
%mask_value(0b10)
> 6003600216

[lightclient]

seems like the undefined macro error isn't triggering correctly fixed

[lightclient]

All feedback addressed, PTAL! 😃