From 3fe52d98694b1a27fd2736619fc5c1bce7d18156 Mon Sep 17 00:00:00 2001
From: chriseth <chris@ethereum.org>
Date: Tue, 7 Sep 2021 15:04:12 +0200
Subject: [PATCH] Run the optimizer only once.

---
 Changelog.md           |  1 +
 libevmasm/Assembly.cpp | 10 +++++++---
 libevmasm/Assembly.h   |  6 +++++-
 3 files changed, 13 insertions(+), 4 deletions(-)

diff --git a/Changelog.md b/Changelog.md
index 5bbd686a3..fc61a1b19 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -15,6 +15,7 @@ Compiler Features:
 
 
 Bugfixes:
+ * Opcode Optimizer: Prevent the optimizer from running multiple times to avoid potential bytecode differences for referenced code.
  * Name Resolver: Fix that when importing an aliased symbol using ``import {AliasedName} from "a.sol"`` it would use the original name of the symbol and not the aliased one.
  * SMTChecker: Fix false negative caused by ``push`` on storage array references returned by internal functions.
  * SMTChecker: Fix false positive in external calls from constructors.
diff --git a/libevmasm/Assembly.cpp b/libevmasm/Assembly.cpp
index dad9635d7..ef465cf35 100644
--- a/libevmasm/Assembly.cpp
+++ b/libevmasm/Assembly.cpp
@@ -409,18 +409,21 @@ Assembly& Assembly::optimise(OptimiserSettings const& _settings)
 	return *this;
 }
 
-map<u256, u256> Assembly::optimiseInternal(
+map<u256, u256> const& Assembly::optimiseInternal(
 	OptimiserSettings const& _settings,
 	std::set<size_t> _tagsReferencedFromOutside
 )
 {
+	if (m_tagReplacements)
+		return *m_tagReplacements;
+
 	// Run optimisation for sub-assemblies.
 	for (size_t subId = 0; subId < m_subs.size(); ++subId)
 	{
 		OptimiserSettings settings = _settings;
 		// Disable creation mode for sub-assemblies.
 		settings.isCreation = false;
-		map<u256, u256> subTagReplacements = m_subs[subId]->optimiseInternal(
+		map<u256, u256> const& subTagReplacements = m_subs[subId]->optimiseInternal(
 			settings,
 			JumpdestRemover::referencedTags(m_items, subId)
 		);
@@ -546,7 +549,8 @@ map<u256, u256> Assembly::optimiseInternal(
 			*this
 		);
 
-	return tagReplacements;
+	m_tagReplacements = move(tagReplacements);
+	return *m_tagReplacements;
 }
 
 LinkerObject const& Assembly::assemble() const
diff --git a/libevmasm/Assembly.h b/libevmasm/Assembly.h
index 4a0779ef7..732aa14a1 100644
--- a/libevmasm/Assembly.h
+++ b/libevmasm/Assembly.h
@@ -165,7 +165,7 @@ protected:
 	/// Does the same operations as @a optimise, but should only be applied to a sub and
 	/// returns the replaced tags. Also takes an argument containing the tags of this assembly
 	/// that are referenced in a super-assembly.
-	std::map<u256, u256> optimiseInternal(OptimiserSettings const& _settings, std::set<size_t> _tagsReferencedFromOutside);
+	std::map<u256, u256> const& optimiseInternal(OptimiserSettings const& _settings, std::set<size_t> _tagsReferencedFromOutside);
 
 	unsigned bytesRequired(unsigned subTagSize) const;
 
@@ -210,6 +210,10 @@ protected:
 	/// This map is used only for sub-assemblies which are not direct sub-assemblies (where path is having more than one value).
 	std::map<std::vector<size_t>, size_t> m_subPaths;
 
+	/// Contains the tag replacements relevant for super-assemblies.
+	/// If set, it means the optimizer has run and we will not run it again.
+	std::optional<std::map<u256, u256>> m_tagReplacements;
+
 	mutable LinkerObject m_assembledObject;
 	mutable std::vector<size_t> m_tagPositionsInBytecode;