From 7aa2ee177546399343b4e79fb0efbf0353395be3 Mon Sep 17 00:00:00 2001
From: Alex Beregszaszi <alex@rtfs.hu>
Date: Tue, 26 Feb 2019 12:12:46 +0000
Subject: [PATCH] More optimiser rules for LT/GT/AND/BYTE

---
 Changelog.md         | 1 +
 libevmasm/RuleList.h | 8 +++++++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/Changelog.md b/Changelog.md
index 753e4dfb2..ea766f70b 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -10,6 +10,7 @@ Compiler Features:
  * Inline Assembly: Instructions unavailable to the currently configured EVM are errors now.
  * SMTChecker: Do not report underflow/overflow if they always revert. This removes false positives when using ``SafeMath``.
  * Static Analyzer: Warn about expressions with custom types when they have no effect.
+ * Optimizer: Add new rules with constants including ``LT``, ``GT``, ``AND`` and ``BYTE``.
  * Optimizer: Add rule for shifts with constants for Constantinople.
  * Optimizer: Combine multiple shifts with constant shift-by values into one.
  * Optimizer: Support shifts in the constant optimiser for Constantinople.
diff --git a/libevmasm/RuleList.h b/libevmasm/RuleList.h
index 7cdf5a96f..7ec3ca461 100644
--- a/libevmasm/RuleList.h
+++ b/libevmasm/RuleList.h
@@ -108,7 +108,7 @@ std::vector<SimplificationRule<Pattern>> simplificationRuleListPart2(
 	Pattern,
 	Pattern,
 	Pattern X,
-	Pattern
+	Pattern Y
 )
 {
 	return std::vector<SimplificationRule<Pattern>> {
@@ -146,6 +146,12 @@ std::vector<SimplificationRule<Pattern>> simplificationRuleListPart2(
 		{{Instruction::SHR, {0, X}}, [=]{ return X; }, false},
 		{{Instruction::SHL, {X, 0}}, [=]{ return u256(0); }, true},
 		{{Instruction::SHR, {X, 0}}, [=]{ return u256(0); }, true},
+		{{Instruction::LT, {X, 0}}, [=]{ return u256(0); }, true},
+		{{Instruction::GT, {X, 0}}, [=]() -> Pattern { return {Instruction::ISZERO, {{Instruction::ISZERO, {X}}}}; }, false},
+		{{Instruction::GT, {X, ~u256(0)}}, [=]{ return u256(0); }, true},
+		{{Instruction::GT, {0, X}}, [=]{ return u256(0); }, true},
+		{{Instruction::AND, {{Instruction::BYTE, {X, Y}}, {u256(0xff)}}}, [=]() -> Pattern { return {Instruction::BYTE, {X, Y}}; }, false},
+		{{Instruction::BYTE, {X, 31}}, [=]() -> Pattern { return {Instruction::AND, {X, u256(0xff)}}; }, false}
 	};
 }