Opcodes stores + loads and Pass-By-Reference Semantics

[tzaffi]

Example PyTeal, with resulting TEAL and explanation:

PyTEAL

@Subroutine(TealType.uint64)
def xyz(x: ScratchVar, y: ScratchVar, z):
    return Seq(
        x.store(x.load() + Int(1)),
        y.store(y.load() + Int(2)),
        x.load() + y.load() + z,
    )


def approval_xyz():
    a = ScratchVar(TealType.uint64, 142)
    b = ScratchVar(TealType.uint64, 143)
    return Seq(
        [
            a.store(Int(100)),
            b.store(Int(200)),
            Pop(a.load() + b.load()),
            Approve(),
        ]
    )

TEAL + Explanation

#pragma version 6
int 100         
store 142       // a@142: 100
int 200
store 143       // b@143: 200
...
int 142
int 143
int 177
callsub xyz_0       
pop
load 142
load 143
+
pop
int 1
return

// previously stored
            // a@142: 100
            // b@143: 200

// xyz
xyz_0:      // >>> 142, 143, 177    >>> @x, @y, z
store 2     // lz@2: 177            2: z
store 1     // ly@1: b@143          1: @y
store 0     // lx@0: a@142          0: @x
load 0      // >>> a@142            >>> @x
load 0      // >>> a@142, a@142     >>> @x, @x
loads       // >>> a@142, 100       >>> @x, x
int 1       // >>> a@142, 100, 1    >>> @x, x, 1
+           // >>> a@142, 101       >>> @x, x+1
stores      // a@142: 101           @x: x+1
load 1      // >>> b@143            >>> @y
load 1      // >>> b@143, b@143     >>> @y, @y
loads       // >>> b@143, 200       >>> @y, y
int 2       // >>> b@143, 200, 2    >>> @y, y, 2
+           // >>> b@143, 202       >>> @y, y+2
stores      // b@143: 202           @y: y+2
load 0      // >>> a@142            >>> @x
loads       // >>> 101              >>> x+1
load 1      // >>> 101, b@143       >>> x+1, @y 
loads       // >>> 101, 202         >>> x+1, y+2
+           // >>> 303              >>> (x+1)+(y+2)
load 2      // >>> 303, 177         >>> (x+1)+(y+2), z
+           // >>> 480              >>> (x+1)+(y+2)+z
retsub

// SUMMARY
// @x: x+1
// @y: y+2
// returns (x+1)+(y+2)+z

[tzaffi]

don't leave as is

[tzaffi]

don't leave as is

[tzaffi]

Code smell: id property can either be an int or Expr based on Slot subclass

[tzaffi]

This new assertion would break any previous code that has a misbehaving getSubroutines() method

[tzaffi]

Code smell: lazy evaluation is no longer valid because a parameter is being introduced. In this case, I believe we're ok (when you follow the branches), but it's preferred to either:

• get rid of the laziness here and take a performance hit
• or split this into a new method that expects the parameter and isn't lazy

[tzaffi]

JUST PLAIN WRONG ...gonna fix

[tzaffi]

Closing for now - too much detritus. Need fresh start with less open ended approach.

[tzaffi]

Might re-base this off of #195