core/vm: improve JUMPDEST analysis

* JUMPDEST analysis is faster because less type conversions are performed.
* The map of JUMPDEST locations is now created lazily at the first JUMP.
* The result of the analysis is kept around for recursive invocations
  through CALL/CALLCODE.

Fixes #1147

1 files changed, 26 insertions, 15 deletions

diff --git a/core/vm/analysis.go b/core/vm/analysis.go
index 264d55cb9..a7aa8da39 100644
--- a/core/vm/analysis.go
+++ b/core/vm/analysis.go
@@ -3,34 +3,45 @@ package vm
 import (
 	"math/big"
 
-	"gopkg.in/fatih/set.v0"
+	"github.com/ethereum/go-ethereum/common"
 )
 
-type destinations struct {
-	set *set.Set
-}
+var bigMaxUint64 = new(big.Int).SetUint64(^uint64(0))
 
-func (d *destinations) Has(dest *big.Int) bool {
-	return d.set.Has(string(dest.Bytes()))
-}
+// destinations stores one map per contract (keyed by hash of code).
+// The maps contain an entry for each location of a JUMPDEST
+// instruction.
+type destinations map[common.Hash]map[uint64]struct{}
 
-func (d *destinations) Add(dest *big.Int) {
-	d.set.Add(string(dest.Bytes()))
+// has checks whether code has a JUMPDEST at dest.
+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.
+	// Don't bother checking for JUMPDEST in that case.
+	if dest.Cmp(bigMaxUint64) > 0 {
+		return false
+	}
+	m, analysed := d[codehash]
+	if !analysed {
+		m = jumpdests(code)
+		d[codehash] = m
+	}
+	_, ok := m[dest.Uint64()]
+	return ok
 }
 
-func analyseJumpDests(code []byte) (dests *destinations) {
-	dests = &destinations{set.New()}
-
+// jumpdests creates a map that contains an entry for each
+// PC location that is a JUMPDEST instruction.
+func jumpdests(code []byte) map[uint64]struct{} {
+	m := make(map[uint64]struct{})
 	for pc := uint64(0); pc < uint64(len(code)); pc++ {
 		var op OpCode = OpCode(code[pc])
 		switch op {
 		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:
 			a := uint64(op) - uint64(PUSH1) + 1
-
 			pc += a
 		case JUMPDEST:
-			dests.Add(big.NewInt(int64(pc)))
+			m[pc] = struct{}{}
 		}
 	}
-	return
+	return m
 }