From b3f43c89b3b884d5d0b8e1a239847f54a291a19b Mon Sep 17 00:00:00 2001
From: Martin Holst Swende <martin@swende.se>
Date: Tue, 21 Mar 2023 07:14:47 -0400
Subject: [PATCH] core/vm: expose jumptable constructors (#26880)

When interacting with geth as a library to e.g. produce state tests, it is desirable to obtain the consensus-correct jumptable definition for a given fork. This changes adds accessors so the instructionset can be obtained and characteristics about opcodes can be inspected.
---
 core/vm/jump_table_export.go | 74 ++++++++++++++++++++++++++++++++++++
 params/config.go             |  6 +--
 2 files changed, 77 insertions(+), 3 deletions(-)
 create mode 100644 core/vm/jump_table_export.go

diff --git a/core/vm/jump_table_export.go b/core/vm/jump_table_export.go
new file mode 100644
index 000000000..0d61b00ed
--- /dev/null
+++ b/core/vm/jump_table_export.go
@@ -0,0 +1,74 @@
+// Copyright 2023 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package vm
+
+import (
+	"errors"
+
+	"github.com/ethereum/go-ethereum/params"
+)
+
+// LookupInstructionSet returns the instructionset for the fork configured by
+// the rules.
+func LookupInstructionSet(rules params.Rules) (JumpTable, error) {
+	switch {
+	case rules.IsPrague:
+		return newShanghaiInstructionSet(), errors.New("prague-fork not defined yet")
+	case rules.IsCancun:
+		return newShanghaiInstructionSet(), errors.New("cancun-fork not defined yet")
+	case rules.IsShanghai:
+		return newShanghaiInstructionSet(), nil
+	case rules.IsMerge:
+		return newMergeInstructionSet(), nil
+	case rules.IsLondon:
+		return newLondonInstructionSet(), nil
+	case rules.IsBerlin:
+		return newBerlinInstructionSet(), nil
+	case rules.IsIstanbul:
+		return newIstanbulInstructionSet(), nil
+	case rules.IsConstantinople:
+		return newConstantinopleInstructionSet(), nil
+	case rules.IsByzantium:
+		return newByzantiumInstructionSet(), nil
+	case rules.IsEIP158:
+		return newSpuriousDragonInstructionSet(), nil
+	case rules.IsEIP150:
+		return newTangerineWhistleInstructionSet(), nil
+	case rules.IsHomestead:
+		return newHomesteadInstructionSet(), nil
+	}
+	return newFrontierInstructionSet(), nil
+}
+
+// Stack returns the mininum and maximum stack requirements.
+func (op *operation) Stack() (int, int) {
+	return op.minStack, op.maxStack
+}
+
+// HasCost returns true if the opcode has a cost. Opcodes which do _not_ have
+// a cost assigned are one of two things:
+// - undefined, a.k.a invalid opcodes,
+// - the STOP opcode.
+// This method can thus be used to check if an opcode is "Invalid (or STOP)".
+func (op *operation) HasCost() bool {
+	// Ideally, we'd check this:
+	//	return op.execute == opUndefined
+	// However, go-lang does now allow that. So we'll just check some other
+	// 'indicators' that this is an invalid op. Alas, STOP is impossible to
+	// filter out
+	return op.dynamicGas != nil || op.constantGas != 0
+}
diff --git a/params/config.go b/params/config.go
index e04b16673..190eb737c 100644
--- a/params/config.go
+++ b/params/config.go
@@ -956,7 +956,7 @@ type Rules struct {
 	IsHomestead, IsEIP150, IsEIP155, IsEIP158               bool
 	IsByzantium, IsConstantinople, IsPetersburg, IsIstanbul bool
 	IsBerlin, IsLondon                                      bool
-	IsMerge, IsShanghai, isCancun, isPrague                 bool
+	IsMerge, IsShanghai, IsCancun, IsPrague                 bool
 }
 
 // Rules ensures c's ChainID is not nil.
@@ -979,7 +979,7 @@ func (c *ChainConfig) Rules(num *big.Int, isMerge bool, timestamp uint64) Rules
 		IsLondon:         c.IsLondon(num),
 		IsMerge:          isMerge,
 		IsShanghai:       c.IsShanghai(timestamp),
-		isCancun:         c.IsCancun(timestamp),
-		isPrague:         c.IsPrague(timestamp),
+		IsCancun:         c.IsCancun(timestamp),
+		IsPrague:         c.IsPrague(timestamp),
 	}
 }