From 29607e93b399d15b46d457d625fb00820cb6bd24 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Mon, 17 May 2021 18:27:17 +0100
Subject: [PATCH] Skip FIO analysis on data continuation

---
 codetrie/codetrie.go | 24 ++++++++++++++++++++++--
 1 file changed, 22 insertions(+), 2 deletions(-)

diff --git a/codetrie/codetrie.go b/codetrie/codetrie.go
index 2999890c3234..5216b41ea18b 100644
--- a/codetrie/codetrie.go
+++ b/codetrie/codetrie.go
@@ -3,6 +3,7 @@ package codetrie
 import (
 	"encoding/binary"
 	"errors"
+	"fmt"
 	"math"
 
 	sszlib "github.com/ferranbt/fastssz"
@@ -32,13 +33,17 @@ type CodeTrie interface {
 	GetTree() (*sszlib.Node, error)
 }
 
+const (
+	FIOUnset = 0xff
+)
+
 type Chunk struct {
 	fio  uint8 // firstInstructionOffset
 	code []byte
 }
 
 func NewChunk() *Chunk {
-	return &Chunk{fio: 0, code: nil}
+	return &Chunk{fio: FIOUnset, code: nil}
 }
 
 func (c *Chunk) Serialize() []byte {
@@ -203,11 +208,21 @@ func Chunkify(code []byte, chunkSize uint) []*Chunk {
 		if i == numChunks-1 {
 			endIdx = uint(len(code))
 		}
-		chunks[i] = &Chunk{fio: 0, code: code[startIdx:endIdx]}
+		chunks[i] = &Chunk{fio: FIOUnset, code: code[startIdx:endIdx]}
 	}
 
 	setFIO(chunks)
 
+	// Sanity check that all chunks were processed
+	for i, _ := range chunks {
+		if i == len(chunks)-1 {
+			break
+		}
+		if chunks[i].fio == FIOUnset {
+			panic(fmt.Sprintf("Chunk %d has unprocessed FIO", i))
+		}
+	}
+
 	return chunks
 }
 
@@ -223,6 +238,11 @@ func setFIO(chunks []*Chunk) {
 			break
 		}
 
+		// This chunk was already processed (it is a data chunk continuation)
+		if chunks[i].fio != FIOUnset {
+			continue
+		}
+
 		for j, op := range chunk.code {
 			opcode := OpCode(op)
 			// Push is the only opcode with immediate