Merge pull request #3580 from ethereum/asm-bitshift-optim

Add simplification rule for bitwise shifting

Changelog.md

@@ -7,6 +7,7 @@ Features:
  * General: Limit the number of errors output in a single run to 256.
  * General: Support accessing dynamic return data in post-byzantium EVMs.
  * Interfaces: Allow overriding external functions in interfaces with public in an implementing contract.
+ * Optimizer: Optimize ``SHL`` and ``SHR`` only involving constants (Constantinople only).
  * Optimizer: Remove useless ``SWAP1`` instruction preceding a commutative instruction (such as ``ADD``, ``MUL``, etc).
  * Optimizer: Replace comparison operators (``LT``, ``GT``, etc) with opposites if preceded by ``SWAP1``, e.g. ``SWAP1 LT`` is replaced with ``GT``.
  * Optimizer: Optimize across ``mload`` if ``msize()`` is not used.

libevmasm/RuleList.h

@@ -89,6 +89,16 @@ std::vector<SimplificationRule<Pattern>> simplificationRuleList(
 			u256 mask = (u256(1) << testBit) - 1;
 			return u256(boost::multiprecision::bit_test(B.d(), testBit) ? B.d() | ~mask : B.d() & mask);
 		}, false},
+		{{Instruction::SHL, {A, B}}, [=]{
+			if (A.d() > 255)
+				return u256(0);
+			return u256(bigint(B.d()) << unsigned(A.d()));
+		}, false},
+		{{Instruction::SHR, {A, B}}, [=]{
+			if (A.d() > 255)
+				return u256(0);
+			return B.d() >> unsigned(A.d());
+		}, false},
 
 		// invariants involving known constants
 		{{Instruction::ADD, {X, 0}}, [=]{ return X; }, false},

scripts/tests.sh

@@ -99,11 +99,18 @@ then
     progress=""
 fi
 
+EVM_VERSIONS="homestead byzantium"
+
+if [ "$CIRCLECI" ] || [ -z "$CI" ]
+then
+EVM_VERSIONS+=" constantinople"
+fi
+
 # And then run the Solidity unit-tests in the matrix combination of optimizer / no optimizer
 # and homestead / byzantium VM, # pointing to that IPC endpoint.
 for optimize in "" "--optimize"
 do
-  for vm in homestead byzantium
+  for vm in $EVM_VERSIONS
   do
     echo "--> Running tests using "$optimize" --evm-version "$vm"..."
     log=""

test/libsolidity/InlineAssembly.cpp

@@ -783,6 +783,8 @@ BOOST_AUTO_TEST_CASE(shift)
 
 BOOST_AUTO_TEST_CASE(shift_constantinople_warning)
 {
+	if (dev::test::Options::get().evmVersion().hasBitwiseShifting())
+		return;
 	CHECK_PARSE_WARNING("{ pop(shl(10, 32)) }", Warning, "The \"shl\" instruction is only available for Constantinople-compatible VMs.");
 	CHECK_PARSE_WARNING("{ pop(shr(10, 32)) }", Warning, "The \"shr\" instruction is only available for Constantinople-compatible VMs.");
 	CHECK_PARSE_WARNING("{ pop(sar(10, 32)) }", Warning, "The \"sar\" instruction is only available for Constantinople-compatible VMs.");

test/libsolidity/SolidityEndToEndTest.cpp

@@ -11141,6 +11141,135 @@ BOOST_AUTO_TEST_CASE(swap_peephole_optimisation)
 	BOOST_CHECK(callContractFunction("div(uint256,uint256)", u256(0), u256(1)) == encodeArgs(u256(0)));
 }
 
+BOOST_AUTO_TEST_CASE(bitwise_shifting_constantinople)
+{
+	if (!dev::test::Options::get().evmVersion().hasBitwiseShifting())
+		return;
+	char const* sourceCode = R"(
+		contract C {
+			function shl(uint a, uint b) returns (uint c) {
+				assembly {
+					a
+					b
+					shl
+					=: c
+				}
+			}
+			function shr(uint a, uint b) returns (uint c) {
+				assembly {
+					a
+					b
+					shr
+					=: c
+				}
+			}
+			function sar(uint a, uint b) returns (uint c) {
+				assembly {
+					a
+					b
+					sar
+					=: c
+				}
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	BOOST_CHECK(callContractFunction("shl(uint256,uint256)", u256(1), u256(2)) == encodeArgs(u256(4)));
+	BOOST_CHECK(callContractFunction("shl(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(1)) == encodeArgs(u256("0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe")));
+	BOOST_CHECK(callContractFunction("shl(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(256)) == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("shr(uint256,uint256)", u256(3), u256(1)) == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shr(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(1)) == encodeArgs(u256("0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")));
+	BOOST_CHECK(callContractFunction("shr(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(255)) == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shr(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(256)) == encodeArgs(u256(0)));
+	BOOST_CHECK(callContractFunction("sar(uint256,uint256)", u256(3), u256(1)) == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("sar(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(1)) == encodeArgs(u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")));
+	BOOST_CHECK(callContractFunction("sar(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(255)) == encodeArgs(u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")));
+	BOOST_CHECK(callContractFunction("sar(uint256,uint256)", u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"), u256(256)) == encodeArgs(u256("0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff")));
+}
+
+BOOST_AUTO_TEST_CASE(bitwise_shifting_constants_constantinople)
+{
+	if (!dev::test::Options::get().evmVersion().hasBitwiseShifting())
+		return;
+	char const* sourceCode = R"(
+		contract C {
+			function shl_1() returns (bool) {
+				uint c;
+				assembly {
+					1
+					2
+					shl
+					=: c
+				}
+				assert(c == 4);
+				return true;
+			}
+			function shl_2() returns (bool) {
+				uint c;
+				assembly {
+					0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+					1
+					shl
+					=: c
+				}
+				assert(c == 0xfffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffe);
+				return true;
+			}
+			function shl_3() returns (bool) {
+				uint c;
+				assembly {
+					0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+					256
+					shl
+					=: c
+				}
+				assert(c == 0);
+				return true;
+			}
+			function shr_1() returns (bool) {
+				uint c;
+				assembly {
+					3
+					1
+					shr
+					=: c
+				}
+				assert(c == 1);
+				return true;
+			}
+			function shr_2() returns (bool) {
+				uint c;
+				assembly {
+					0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+					1
+					shr
+					=: c
+				}
+				assert(c == 0x7fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff);
+				return true;
+			}
+			function shr_3() returns (bool) {
+				uint c;
+				assembly {
+					0xffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff
+					256
+					shr
+					=: c
+				}
+				assert(c == 0);
+				return true;
+			}
+		}
+	)";
+	compileAndRun(sourceCode);
+	BOOST_CHECK(callContractFunction("shl_1()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shl_2()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shl_3()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shr_1()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shr_2()") == encodeArgs(u256(1)));
+	BOOST_CHECK(callContractFunction("shr_3()") == encodeArgs(u256(1)));
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }