Backport #346 #347 #349

[mohanson]

When the Rust interpreter executes instructions, it uses a huge match to match opcodes.

let op = extract_opcode(inst);
match op {
    insts::OP_SUB => {}
    insts::OP_SUBW => {}
    insts::OP_ADD => {}
    insts::OP_ADDW => {}
    ...
}

This leads to a problem, the function is too big and it needs to store too many variables on the stack. In some cases (such as calling vm in vm), It will cause stack overflow.

@xxuejie's works can avoid this problem. In the worst case (vm calls vm, loop 57 times), only about 900K stack space is now needed.

Additional change: ckb currently uses paste 1.0.6, so I downgraded the paste version of ckb-vm.

[xxuejie]

That reminds me a question: do we need to move ThreadFactory to heap? I'm not entirely sure how far LLVM is willing to go here. Maybe moving ThreadFactory to heap will save further stack space, maybe not, just not sure.

[XuJiandong]

Can we cast op into u32 and then use with match?

[mohanson]

That reminds me a question: do we need to move ThreadFactory to heap? I'm not entirely sure how far LLVM is willing to go here. Maybe moving ThreadFactory to heap will save further stack space, maybe not, just not sure.

I did a test, if the ThreadFactory is moved to the heap, it can save ~7K stack space for each vm

[xxuejie]

7K * 57 == 399K, which can be a rather valuable save. But we can leave this to a future change.

[mohanson]

Can we cast op into u32 and then use with match?

It might help a little, but not enough to fix this bug