add basic block merging threshold

[plafer]

Adds a threshold when merging basic blocks after which we won't merge more blocks in.

Benchmarks for 2 different values (quite similar):

• on branch next:
  • deserialize_std_lib: 14.6ms
  • stdlib compilation: 120ms
• MAX_OPERATIONS_PER_BASIC_BLOCK_WHEN_MERGING = 1000:
  • deserialize_std_lib: 3.4 ms
  • stdlib compilation: 62 ms
• MAX_OPERATIONS_PER_BASIC_BLOCK_WHEN_MERGING = 2500:
  • deserialize_std_lib: 4.8ms
  • stdlib compilation: 65ms

Note that deserialize_std_lib time is directly proportional to the size of the stdlib serialized binary. So with the constant at 1000 or 2500, it roughly halves the size of the binary (i.e. ~0.6MB).

[bobbinth]

Looks good! Thank you!

I updated the methodology used for merging. In terms of the binary size, the new approach is roughly equivalent to the the 2500 threshold in the old one. But I'm hoping it will result in smaller runtime penalties. Curious what you think though.