Remove unnecessary masking of the result of known short instructions

4 files changed, 110 insertions, 0 deletions

diff --git a/Changelog.md b/Changelog.md
index faeb628b..207e2c21 100644
--- a/Changelog.md
+++ b/Changelog.md
@@ -1,6 +1,7 @@
 ### 0.4.24 (unreleased)
 
 Features:
+ * Optimizer: Remove unnecessary masking of the result of known short instructions (``ADDRESS``, ``CALLER``, ``ORIGIN`` and ``COINBASE``).
 
 
 Bugfixes:
diff --git a/libevmasm/RuleList.h b/libevmasm/RuleList.h
index abcf170c..2b7da01b 100644
--- a/libevmasm/RuleList.h
+++ b/libevmasm/RuleList.h
@@ -174,6 +174,26 @@ std::vector<SimplificationRule<Pattern>> simplificationRuleList(
 		});
 	}
 
+	for (auto const& op: std::vector<Instruction>{
+		Instruction::ADDRESS,
+		Instruction::CALLER,
+		Instruction::ORIGIN,
+		Instruction::COINBASE
+	})
+	{
+		u256 const mask = (u256(1) << 160) - 1;
+		rules.push_back({
+			{Instruction::AND, {{op, mask}}},
+			[=]() -> Pattern { return op; },
+			false
+		});
+		rules.push_back({
+			{Instruction::AND, {{mask, op}}},
+			[=]() -> Pattern { return op; },
+			false
+		});
+	}
+
 	// Double negation of opcodes with boolean result
 	for (auto const& op: std::vector<Instruction>{
 		Instruction::EQ,
diff --git a/test/libevmasm/Optimiser.cpp b/test/libevmasm/Optimiser.cpp
index 089be45d..4b399a14 100644
--- a/test/libevmasm/Optimiser.cpp
+++ b/test/libevmasm/Optimiser.cpp
@@ -1072,6 +1072,75 @@ BOOST_AUTO_TEST_CASE(cse_sub_zero)
 	});
 }
 
+BOOST_AUTO_TEST_CASE(cse_remove_unwanted_masking_of_address)
+{
+	vector<Instruction> ops{
+		Instruction::ADDRESS,
+		Instruction::CALLER,
+		Instruction::ORIGIN,
+		Instruction::COINBASE
+	};
+	for (auto const& op: ops)
+	{
+		checkCSE({
+			u256("0xffffffffffffffffffffffffffffffffffffffff"),
+			op,
+			Instruction::AND
+		}, {
+			op
+		});
+
+		checkCSE({
+			op,
+			u256("0xffffffffffffffffffffffffffffffffffffffff"),
+			Instruction::AND
+		}, {
+			op
+		});
+
+		// do not remove mask for other masking
+		checkCSE({
+			u256(1234),
+			op,
+			Instruction::AND
+		}, {
+			op,
+			u256(1234),
+			Instruction::AND
+		});
+
+		checkCSE({
+			op,
+			u256(1234),
+			Instruction::AND
+		}, {
+			u256(1234),
+			op,
+			Instruction::AND
+		});
+	}
+
+	// leave other opcodes untouched
+	checkCSE({
+		u256("0xffffffffffffffffffffffffffffffffffffffff"),
+		Instruction::CALLVALUE,
+		Instruction::AND
+	}, {
+		Instruction::CALLVALUE,
+		u256("0xffffffffffffffffffffffffffffffffffffffff"),
+		Instruction::AND
+	});
+
+	checkCSE({
+		Instruction::CALLVALUE,
+		u256("0xffffffffffffffffffffffffffffffffffffffff"),
+		Instruction::AND
+	}, {
+		u256("0xffffffffffffffffffffffffffffffffffffffff"),
+		Instruction::CALLVALUE,
+		Instruction::AND
+	});
+}
 
 BOOST_AUTO_TEST_SUITE_END()
 
diff --git a/test/libsolidity/SolidityEndToEndTest.cpp b/test/libsolidity/SolidityEndToEndTest.cpp
index 789b89d1..71386010 100644
--- a/test/libsolidity/SolidityEndToEndTest.cpp
+++ b/test/libsolidity/SolidityEndToEndTest.cpp
@@ -11881,6 +11881,26 @@ BOOST_AUTO_TEST_CASE(bitwise_shifting_constants_constantinople)
 	BOOST_CHECK(callContractFunction("shr_3()") == encodeArgs(u256(1)));
 }
 
+BOOST_AUTO_TEST_CASE(senders_balance)
+{
+	char const* sourceCode = R"(
+		contract C {
+			function f() public view returns (uint) {
+				return msg.sender.balance;
+			}
+		}
+		contract D {
+			C c = new C();
+			constructor() payable { }
+			function f() public view returns (uint) {
+				return c.f();
+			}
+		}
+	)";
+	compileAndRun(sourceCode, 27, "D");
+	BOOST_CHECK(callContractFunction("f()") == encodeArgs(u256(27)));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }