From d5a79934dc0542bc3ed74f7561651eecdf62a3a1 Mon Sep 17 00:00:00 2001
From: Nick Johnson <arachnid@notdot.net>
Date: Thu, 1 Jun 2017 18:42:20 +0100
Subject: [PATCH] core/vm: Use a bitmap instead of a map for jumpdest analysis
 t push --force

---
 core/vm/analysis.go | 26 ++++++++++++--------------
 1 file changed, 12 insertions(+), 14 deletions(-)

diff --git a/core/vm/analysis.go b/core/vm/analysis.go
index a0f6158217..d5f048d1d0 100644
--- a/core/vm/analysis.go
+++ b/core/vm/analysis.go
@@ -22,41 +22,39 @@ import (
 	"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).
 // The maps contain an entry for each location of a JUMPDEST
 // instruction.
-type destinations map[common.Hash]map[uint64]struct{}
+type destinations map[common.Hash][]byte
 
 // 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.
+	// PC cannot go beyond len(code) and certainly can't be bigger than 63bits.
 	// 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
 	}
+
 	m, analysed := d[codehash]
 	if !analysed {
 		m = jumpdests(code)
 		d[codehash] = m
 	}
-	_, ok := m[dest.Uint64()]
-	return ok
+	return (m[udest/8] & (1 << (udest % 8))) != 0
 }
 
 // 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{})
+func jumpdests(code []byte) []byte {
+	m := make([]byte, len(code)/8+1)
 	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:
+		op := OpCode(code[pc])
+		if op == JUMPDEST {
+			m[pc/8] |= 1 << (pc % 8)
+		} else if op >= PUSH1 && op <= PUSH32 {
 			a := uint64(op) - uint64(PUSH1) + 1
 			pc += a
-		case JUMPDEST:
-			m[pc] = struct{}{}
 		}
 	}
 	return m