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Merge pull request #14570 from Arachnid/jumpdestanalysis

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core/vm: Use a bitmap instead of a map for jumpdest analysis
This commit is contained in:
Péter Szilágyi 2017-06-01 21:44:50 +03:00 committed by GitHub
commit ac92d7c411
1 changed files with 12 additions and 14 deletions
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26
core/vm/analysis.go
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@ -22,41 +22,39 @@ import (
"github.com/ethereum/go-ethereum/common" "github.com/ethereum/go-ethereum/common"
) )
var bigMaxUint64 = new(big.Int).SetUint64(^uint64(0))
// destinations stores one map per contract (keyed by hash of code). // destinations stores one map per contract (keyed by hash of code).
// The maps contain an entry for each location of a JUMPDEST // The maps contain an entry for each location of a JUMPDEST
// instruction. // instruction.
type destinations map[common.Hash]map[uint64]struct{} type destinations map[common.Hash][]byte
// has checks whether code has a JUMPDEST at dest. // has checks whether code has a JUMPDEST at dest.
func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool { func (d destinations) has(codehash common.Hash, code []byte, dest *big.Int) bool {
// PC cannot go beyond len(code) and certainly can't be bigger than 64bits. // PC cannot go beyond len(code) and certainly can't be bigger than 63bits.
// Don't bother checking for JUMPDEST in that case. // Don't bother checking for JUMPDEST in that case.
if dest.Cmp(bigMaxUint64) > 0 { udest := dest.Uint64()
if dest.BitLen() >= 63 || udest >= uint64(len(code)) {
return false return false
} }
m, analysed := d[codehash] m, analysed := d[codehash]
if !analysed { if !analysed {
m = jumpdests(code) m = jumpdests(code)
d[codehash] = m d[codehash] = m
} }
_, ok := m[dest.Uint64()] return (m[udest/8] & (1 << (udest % 8))) != 0
return ok
} }
// jumpdests creates a map that contains an entry for each // jumpdests creates a map that contains an entry for each
// PC location that is a JUMPDEST instruction. // PC location that is a JUMPDEST instruction.
func jumpdests(code []byte) map[uint64]struct{} { func jumpdests(code []byte) []byte {
m := make(map[uint64]struct{}) m := make([]byte, len(code)/8+1)
for pc := uint64(0); pc < uint64(len(code)); pc++ { for pc := uint64(0); pc < uint64(len(code)); pc++ {
var op OpCode = OpCode(code[pc]) op := OpCode(code[pc])
switch op { if op == JUMPDEST {
case PUSH1, PUSH2, PUSH3, PUSH4, PUSH5, PUSH6, PUSH7, PUSH8, PUSH9, PUSH10, PUSH11, PUSH12, PUSH13, PUSH14, PUSH15, PUSH16, PUSH17, PUSH18, PUSH19, PUSH20, PUSH21, PUSH22, PUSH23, PUSH24, PUSH25, PUSH26, PUSH27, PUSH28, PUSH29, PUSH30, PUSH31, PUSH32: m[pc/8] |= 1 << (pc % 8)
} else if op >= PUSH1 && op <= PUSH32 {
a := uint64(op) - uint64(PUSH1) + 1 a := uint64(op) - uint64(PUSH1) + 1
pc += a pc += a
case JUMPDEST:
m[pc] = struct{}{}
} }
} }
return m return m