2315: changes in gascosts (ethereum#2676)

EIPS/eip-2315.md

@@ -76,59 +76,62 @@ This should jump into a subroutine, back out and stop.
 
 Bytecode: `0x6004b300b2b7`
 
-
 |  Pc   |      Op     | Cost |   Stack   |   RStack  |
 |-------|-------------|------|-----------|-----------|
 |    0  |      PUSH1  |    3 |        [] |        [] |
-|    2  |    JUMPSUB  |    8 |       [4] |        [] |
-|    5  |  RETURNSUB  |    2 |        [] |      [ 2] |
+|    2  |    JUMPSUB  |   10 |       [4] |        [] |
+|    5  |  RETURNSUB  |    5 |        [] |      [ 2] |
 |    3  |       STOP  |    0 |        [] |        [] |
 
+Output: 0x
+Consumed gas: `18`
+
 ### Two levels of subroutines
 
 This should execute fine, going into one two depths of subroutines
+
 Bytecode: `0x6800000000000000000cb300b26011b3b7b2b7`
 
 |  Pc   |      Op     | Cost |   Stack   |   RStack  |
 |-------|-------------|------|-----------|-----------|
 |    0  |      PUSH9  |    3 |        [] |        [] |
-|   10  |    JUMPSUB  |    8 |      [12] |        [] |
+|   10  |    JUMPSUB  |   10 |      [12] |        [] |
 |   13  |      PUSH1  |    3 |        [] |      [10] |
-|   15  |    JUMPSUB  |    8 |      [17] |      [10] |
-|   18  |  RETURNSUB  |    2 |        [] |   [10,15] |
-|   16  |  RETURNSUB  |    2 |        [] |      [10] |
+|   15  |    JUMPSUB  |   10 |      [17] |      [10] |
+|   18  |  RETURNSUB  |    5 |        [] |   [10,15] |
+|   16  |  RETURNSUB  |    5 |        [] |      [10] |
 |   11  |       STOP  |    0 |        [] |        [] |
 
+Consumed gas: `36`
 
 ### Failure 1: invalid jump
 
-This should fail, since the given `location` is outside of the code-range. The code is the same as previous example,
-except that the pushed `location` is `0x01000000000000000c` instead of `0x0c`.
+This should fail, since the given location is outside of the code-range. The code is the same as previous example, 
+except that the pushed location is `0x01000000000000000c` instead of `0x0c`.
 
-Bytecode: `0x6801000000000000000cb300b26011b3b7b2b7	`
+Bytecode: `0x6801000000000000000cb300b26011b3b7b2b7`
 
 |  Pc   |      Op     | Cost |   Stack   |   RStack  |
 |-------|-------------|------|-----------|-----------|
 |    0  |      PUSH9  |    3 |        [] |        [] |
-|   10  |    JUMPSUB  |    8 |[18446744073709551628] |        [] |
+|   10  |    JUMPSUB  |   10 |[18446744073709551628] |        [] |
 
 ```
-Error: at pc=10, op=JUMPSUB: evm: invalid jump destination
+Error: at pc=10, op=JUMPSUB: invalid jump destination
 ```
 
 ### Failure 2: shallow `return stack`
 
-This should fail at first opcode, due to shallow `return stack`
+This should fail at first opcode, due to shallow `return_stack`
 
 Bytecode: `0xb75858` (`RETURNSUB`, `PC`, `PC`)
 
-
 |  Pc   |      Op     | Cost |   Stack   |   RStack  |
 |-------|-------------|------|-----------|-----------|
-|    0  |  RETURNSUB  |    2 |        [] |        [] |
+|    0  |  RETURNSUB  |    5 |        [] |        [] |
 
 ```
-Error: at pc=0, op=RETURNSUB: evm: invalid retsub
+Error: at pc=0, op=RETURNSUB: invalid retsub
 ```
 
 ### Subroutine at end of code
@@ -143,49 +146,58 @@ Bytecode: `0x600556b2b75b6003b3`
 |    2  |       JUMP  |    8 |       [5] |        [] |
 |    5  |   JUMPDEST  |    1 |        [] |        [] |
 |    6  |      PUSH1  |    3 |        [] |        [] |
-|    8  |    JUMPSUB  |    8 |       [3] |        [] |
-|    4  |  RETURNSUB  |    2 |        [] |      [ 8] |
+|    8  |    JUMPSUB  |   10 |       [3] |        [] |
+|    4  |  RETURNSUB  |    5 |        [] |      [ 8] |
 |    9  |       STOP  |    0 |        [] |        [] |
 
-Consumed gas: `25`
+Consumed gas: `30`
 
 ### Error on "walk-into-subroutine"
 
 In this example, the code 'walks' into a subroutine, which is not allowed, and causes an error
 
+Bytecode: `0xb2b700`
+
+
 |  Pc   |      Op     | Cost |   Stack   |   RStack  |
 |-------|-------------|------|-----------|-----------|
-|    0  |   BEGINSUB  |    1 |        [] |        [] |
-
+|    0  |   BEGINSUB  |    2 |        [] |        [] |
 
 ```
 Error: at pc=0, op=BEGINSUB: invalid subroutine entry
 ```
+
 **Note 5**: The content of the error message, (`invalid subroutine entry`) is implementation-specific.
 
 ## Implementations
 
-Three clients have implemented the previous version of proposal:
+Three clients have implemented this (or an earlier version of) this proposal:
 
 - [geth](https://github.com/ethereum/go-ethereum/pull/20619) .
 - [besu](https://github.com/hyperledger/besu/pull/717), and
 - [openethereum](https://github.com/openethereum/openethereum/pull/11629).
 
-The changes for the current version are trivial.
 
 ### Costs and Codes
 
-We suggest that the cost of `BEGINSUB` be _base_, `JUMPSUB` be _mid_, and `RETURNSUB` be _verylow_.
- Measurement will tell.  We suggest the following opcodes:
+We suggest that the cost of 
+
+- `BEGINSUB` be _base_ (`2`)
+  - Although formally specified, the cost of `BEGINSUB` does not matter in practice, since `BEGINSUB` never executes without error. 
+- `JUMPSUB` be _high_ (`10`)
+  - This is the same as `JUMPI`, and `2` more than `JUMP`.
+- `RETURNSUB` be _low_ (`5`).
+
+Benchmarking might be needed to tell if the costs are well-balanced. 
+
+We suggest the following opcodes:
 
 ```
 0xb2 BEGINSUB
 0xb3 JUMPSUB
 0xb7 RETURNSUB
 ```
 
-**Note 6**: Although specified at _base_, the cost of `BEGINSUB` does not matter in practice, since `BEGINSUB` never executes without error. 
-
 ## Security Considerations
 
 These changes do introduce new flow control instructions, so any software which does static/dynamic analysis of evm-code