Motivation: To sanity check tests are executing as intended, in particular benchmark tests. More background here:

• benchmarks: known refactorings and further iteration ideas #1704 (comment)

One way to verify correct test execution would be to verify in the test framework that the intended opcode count was indeed triggered in the EVM. evmone already has an internal "histogram" feature that does exactly this; we need only enable the interface on the t8n tool.

Here's a proposal for that interface:

Flag, Output and Behavior

--opcode.freq=freq.json

Existing flags can be found here:

Contents of freq.json

{
  "MSTORE": 1,
  "PUSH1": 4,
  "RETURN": 1
}

If an opcode is omitted, its frequency is zero.