From 78745551c077bf54151202138c2629f288769561 Mon Sep 17 00:00:00 2001
From: Determinant <tederminant@gmail.com>
Date: Tue, 15 Sep 2020 23:55:34 -0400
Subject: WIP: geth-tavum

---
 core/vm/contract.go | 36 ++++++++++++++++++++++++++++++++----
 1 file changed, 32 insertions(+), 4 deletions(-)

(limited to 'core/vm/contract.go')

diff --git a/core/vm/contract.go b/core/vm/contract.go
index ed17402..915193d 100644
--- a/core/vm/contract.go
+++ b/core/vm/contract.go
@@ -19,7 +19,8 @@ package vm
 import (
 	"math/big"
 
-	"github.com/ava-labs/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/holiman/uint256"
 )
 
 // ContractRef is a reference to the contract's backing object
@@ -81,18 +82,43 @@ func NewContract(caller ContractRef, object ContractRef, value *big.Int, gas uin
 	return c
 }
 
-func (c *Contract) validJumpdest(dest *big.Int) bool {
-	udest := dest.Uint64()
+func (c *Contract) validJumpdest(dest *uint256.Int) bool {
+	udest, overflow := dest.Uint64WithOverflow()
 	// 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.BitLen() >= 63 || udest >= uint64(len(c.Code)) {
+	if overflow || udest >= uint64(len(c.Code)) {
 		return false
 	}
 	// Only JUMPDESTs allowed for destinations
 	if OpCode(c.Code[udest]) != JUMPDEST {
 		return false
 	}
+	return c.isCode(udest)
+}
+
+func (c *Contract) validJumpSubdest(udest uint64) bool {
+	// PC cannot go beyond len(code) and certainly can't be bigger than 63 bits.
+	// Don't bother checking for BEGINSUB in that case.
+	if int64(udest) < 0 || udest >= uint64(len(c.Code)) {
+		return false
+	}
+	// Only BEGINSUBs allowed for destinations
+	if OpCode(c.Code[udest]) != BEGINSUB {
+		return false
+	}
+	return c.isCode(udest)
+}
+
+// isCode returns true if the provided PC location is an actual opcode, as
+// opposed to a data-segment following a PUSHN operation.
+func (c *Contract) isCode(udest uint64) bool {
+	// Do we already have an analysis laying around?
+	if c.analysis != nil {
+		return c.analysis.codeSegment(udest)
+	}
 	// Do we have a contract hash already?
+	// If we do have a hash, that means it's a 'regular' contract. For regular
+	// contracts ( not temporary initcode), we store the analysis in a map
 	if c.CodeHash != (common.Hash{}) {
 		// Does parent context have the analysis?
 		analysis, exist := c.jumpdests[c.CodeHash]
@@ -102,6 +128,8 @@ func (c *Contract) validJumpdest(dest *big.Int) bool {
 			analysis = codeBitmap(c.Code)
 			c.jumpdests[c.CodeHash] = analysis
 		}
+		// Also stash it in current contract for faster access
+		c.analysis = analysis
 		return analysis.codeSegment(udest)
 	}
 	// We don't have the code hash, most likely a piece of initcode not already
-- 
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