spread last call argument v2

[ozanh]

This PR is created in favor of feedback in #299

• No new OpCode is introduced.
• OpCall has two operands now. Existing compiled scripts do not work, recompilation is required.
• OpCall second operand is used to denote whether last stack object is expanded/spread or not, which must be valid tengo Object *Array, *ImmutableArray or for custom user types Spreader.

[d5]

It looks good to me. But I'm not sure if we need a Spreader interface given that it will always be array type, which is not difficult to compose. Do you have any good use cases for that?

[ozanh]

I don't have a solid use case for Spreader, it can be removed. User can expose any method to return an array.

[d5]

Also, I'd appreciate it if you could update documentation as well.

[ozanh]

I will remove Spreader interface and add documentation tomorrow 👍

[ozanh]

I hope docs are OK because I am not good at English. I added some missing notes about CLI and keyword selectors as well. Closes #301, Closes #265

[d5]

It looks good to me. @geseq Want to take a look?

[d5]

@geseq please review this PR and feel free to merge/release. This should be v2.6.0.

[geseq]

@ozanh can you post the before and after fib(35) benchmarks in cmd/bench/main.go?

[ozanh]

@geseq cmd/bench/main.go results
OLD

-------------------------------------
fibonacci(35)
-------------------------------------
Result:  9227465
Go:      72.629763ms
Parser:  14.569µs
Compile: 75.709µs
VM:      3.015807538s
-------------------------------------
fibonacci(35) (tail-call #1)
-------------------------------------
Result:  9227465
Go:      65.526133ms
Parser:  16.425µs
Compile: 66.364µs
VM:      3.17805909s
-------------------------------------
fibonacci(35) (tail-call #2)
-------------------------------------
Result:  9227465
Go:      230ns
Parser:  16.279µs
Compile: 60.879µs
VM:      25.062µs

NEW

-------------------------------------
fibonacci(35)
-------------------------------------
Result:  9227465
Go:      62.885487ms
Parser:  15.205µs
Compile: 79.682µs
VM:      2.998246515s
-------------------------------------
fibonacci(35) (tail-call #1)
-------------------------------------
Result:  9227465
Go:      64.565828ms
Parser:  16.822µs
Compile: 68.22µs
VM:      3.084532036s
-------------------------------------
fibonacci(35) (tail-call #2)
-------------------------------------
Result:  9227465
Go:      245ns
Parser:  16.211µs
Compile: 57.697µs
VM:      11.635µs

These are my benchstat comparisons using similar fibonacci functions

name      old time/op    new time/op    delta
Fib-8        2.98s ± 1%     2.98s ± 1%    ~     (p=0.436 n=10+10)
FibTC1-8     3.17s ± 1%     3.11s ± 1%  -1.72%  (p=0.000 n=10+10)
FibTC2-8    53.9µs ± 1%    54.0µs ± 1%    ~     (p=0.143 n=10+10)

name      old alloc/op   new alloc/op   delta
Fib-8        313MB ± 0%     313MB ± 0%    ~     (p=0.881 n=9+9)
FibTC1-8     358MB ± 0%     358MB ± 0%  +0.00%  (p=0.000 n=9+10)
FibTC2-8     126kB ± 0%     126kB ± 0%  +0.06%  (p=0.000 n=10+9)

name      old allocs/op  new allocs/op  delta
Fib-8        39.1M ± 0%     39.1M ± 0%  +0.00%  (p=0.003 n=10+9)
FibTC1-8     44.8M ± 0%     44.8M ± 0%  +0.00%  (p=0.000 n=9+10)
FibTC2-8       462 ± 0%       467 ± 0%  +1.08%  (p=0.000 n=10+10)