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package vm
import (
"math/big"
"time"
"github.com/ethereum/go-ethereum/logger"
"github.com/ethereum/go-ethereum/logger/glog"
)
// optimeProgram optimises a JIT program creating segments out of program
// instructions. Currently covered are multi-pushes and static jumps
func optimiseProgram(program *Program) {
var load []instruction
var (
statsJump = 0
statsPush = 0
)
if glog.V(logger.Debug) {
glog.Infof("optimising %x\n", program.Id[:4])
tstart := time.Now()
defer func() {
glog.Infof("optimised %x done in %v with JMP: %d PSH: %d\n", program.Id[:4], time.Since(tstart), statsJump, statsPush)
}()
}
for i := 0; i < len(program.instructions); i++ {
instr := program.instructions[i].(instruction)
switch {
case instr.op.IsPush():
load = append(load, instr)
case instr.op.IsStaticJump():
if len(load) == 0 {
continue
}
// if the push load is greater than 1, finalise that
// segment first
if len(load) > 2 {
seg, size := makePushSeg(load[:len(load)-1])
program.instructions[i-size-1] = seg
statsPush++
}
// create a segment consisting of a pre determined
// jump, destination and validity.
seg := makeStaticJumpSeg(load[len(load)-1].data, program)
program.instructions[i-1] = seg
statsJump++
load = nil
default:
// create a new N pushes segment
if len(load) > 1 {
seg, size := makePushSeg(load)
program.instructions[i-size] = seg
statsPush++
}
load = nil
}
}
}
// makePushSeg creates a new push segment from N amount of push instructions
func makePushSeg(instrs []instruction) (pushSeg, int) {
var (
data []*big.Int
gas = new(big.Int)
)
for _, instr := range instrs {
data = append(data, instr.data)
gas.Add(gas, instr.gas)
}
return pushSeg{data, gas}, len(instrs)
}
// makeStaticJumpSeg creates a new static jump segment from a predefined
// destination (PUSH, JUMP).
func makeStaticJumpSeg(to *big.Int, program *Program) jumpSeg {
gas := new(big.Int)
gas.Add(gas, _baseCheck[PUSH1].gas)
gas.Add(gas, _baseCheck[JUMP].gas)
contract := &Contract{Code: program.code}
pos, err := jump(program.mapping, program.destinations, contract, to)
return jumpSeg{pos, err, gas}
}
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