Merge pull request #6594 from ethereum/adjustCodeMetric

Increase code cost for branching statements.

libyul/optimiser/Metrics.cpp

@@ -63,6 +63,16 @@ void CodeSize::visit(Statement const& _statement)
 {
 	if (_statement.type() == typeid(FunctionDefinition) && m_ignoreFunctions)
 		return;
+	else if (
+		_statement.type() == typeid(If) ||
+		_statement.type() == typeid(Break) ||
+		_statement.type() == typeid(Continue)
+	)
+		m_size += 2;
+	else if (_statement.type() == typeid(ForLoop))
+		m_size += 3;
+	else if (_statement.type() == typeid(Switch))
+		m_size += 1 + 2 * boost::get<Switch>(_statement).cases.size();
 	else if (!(
 		_statement.type() == typeid(Block) ||
 		_statement.type() == typeid(ExpressionStatement) ||

libyul/optimiser/Metrics.h

@@ -37,6 +37,11 @@ namespace yul
  *  - variable references
  *  - variable declarations (only the right hand side has a cost)
  *  - assignments (only the value has a cost)
+ *
+ * As another exception, each statement incurs and additional cost of one
+ * per jump/branch. This means if, break and continue statements have a cost of 2,
+ * switch statements have a cost of 1 plus the number of cases times two,
+ * and for loops cost 3.
  */
 class CodeSize: public ASTWalker
 {

test/cmdlineTests/gas_test_abiv2_optimize_yul/output

@@ -2,7 +2,7 @@
 ======= gas_test_abiv2_optimize_yul/input.sol:C =======
 Gas estimation:
 construction:
-   651 + 616600 = 617251
+   645 + 608800 = 609445
 external:
    a():	429
    b(uint256):	884

test/libyul/Metrics.cpp

@@ -110,6 +110,69 @@ BOOST_AUTO_TEST_CASE(assignment_complex)
 	BOOST_CHECK_EQUAL(codeSize("{ let a let x := mload(a) a := sload(x) }"), 2);
 }
 
+BOOST_AUTO_TEST_CASE(empty_for_loop)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ for {} 1 {} {} }"
+	), 4);
+}
+
+BOOST_AUTO_TEST_CASE(break_statement)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ for {} 1 {} { break } }"
+	), 6);
+}
+
+BOOST_AUTO_TEST_CASE(continue_statement)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ for {} 1 {} { continue } }"
+	), 6);
+}
+
+BOOST_AUTO_TEST_CASE(regular_for_loop)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ for { let x := 0 } lt(x, 10) { x := add(x, 1) } { mstore(x, 1) } }"
+	), 10);
+}
+
+BOOST_AUTO_TEST_CASE(if_statement)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ if 1 {} }"
+	), 3);
+}
+
+BOOST_AUTO_TEST_CASE(switch_statement_tiny)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ switch calldatasize() default {} }"
+	), 4);
+}
+
+BOOST_AUTO_TEST_CASE(switch_statement_small)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ switch calldatasize() case 0 {} default {} }"
+	), 6);
+}
+
+BOOST_AUTO_TEST_CASE(switch_statement_medium)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ switch calldatasize() case 0 {} case 1 {} case 2 {} }"
+	), 8);
+}
+
+BOOST_AUTO_TEST_CASE(switch_statement_large)
+{
+	BOOST_CHECK_EQUAL(codeSize(
+		"{ switch calldatasize() case 0 {} case 1 {} case 2 {} default {} }"
+	), 10);
+}
+
 BOOST_AUTO_TEST_SUITE_END()
 
 }

test/libyul/yulOptimizerTests/fullSuite/abi_example1.yul

@@ -476,44 +476,30 @@
 //             i := add(i, 1)
 //         }
 //         {
-//             let _4 := mload(srcPtr)
+//             abi_encode_t_array$_t_contract$_C_$55_$3_memory_to_t_array$_t_address_$3_memory_ptr(mload(srcPtr), pos)
-//             let pos_1 := pos
-//             let srcPtr_1 := _4
-//             let i_1 := _2
-//             for {
-//             }
-//             lt(i_1, 0x3)
-//             {
-//                 i_1 := add(i_1, 1)
-//             }
-//             {
-//                 mstore(pos_1, and(mload(srcPtr_1), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF))
-//                 srcPtr_1 := add(srcPtr_1, _1)
-//                 pos_1 := add(pos_1, _1)
-//             }
 //             srcPtr := add(srcPtr, _1)
 //             pos := add(pos, 0x60)
 //         }
-//         let _5 := mload(64)
+//         let _4 := mload(64)
-//         let _6 := mload(_1)
+//         let _5 := mload(_1)
-//         if slt(sub(_5, _6), 128)
+//         if slt(sub(_4, _5), 128)
 //         {
 //             revert(_2, _2)
 //         }
-//         let offset := calldataload(add(_6, 64))
+//         let offset := calldataload(add(_5, 64))
-//         let _7 := 0xffffffffffffffff
+//         let _6 := 0xffffffffffffffff
-//         if gt(offset, _7)
+//         if gt(offset, _6)
 //         {
 //             revert(_2, _2)
 //         }
-//         let value2 := abi_decode_t_array$_t_uint256_$dyn_memory_ptr(add(_6, offset), _5)
+//         let value2 := abi_decode_t_array$_t_uint256_$dyn_memory_ptr(add(_5, offset), _4)
-//         let offset_1 := calldataload(add(_6, 96))
+//         let offset_1 := calldataload(add(_5, 96))
-//         if gt(offset_1, _7)
+//         if gt(offset_1, _6)
 //         {
 //             revert(_2, _2)
 //         }
-//         let value3 := abi_decode_t_array$_t_array$_t_uint256_$2_memory_$dyn_memory_ptr(add(_6, offset_1), _5)
+//         let value3 := abi_decode_t_array$_t_array$_t_uint256_$2_memory_$dyn_memory_ptr(add(_5, offset_1), _4)
-//         sstore(calldataload(_6), calldataload(add(_6, _1)))
+//         sstore(calldataload(_5), calldataload(add(_5, _1)))
 //         sstore(value2, value3)
 //         sstore(_2, pos)
 //     }
@@ -601,6 +587,22 @@
 //             src := add(src, _1)
 //         }
 //     }
+//     function abi_encode_t_array$_t_contract$_C_$55_$3_memory_to_t_array$_t_address_$3_memory_ptr(value, pos)
+//     {
+//         let srcPtr := value
+//         let i := 0
+//         for {
+//         }
+//         lt(i, 0x3)
+//         {
+//             i := add(i, 1)
+//         }
+//         {
+//             mstore(pos, and(mload(srcPtr), 0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF))
+//             srcPtr := add(srcPtr, 0x20)
+//             pos := add(pos, 0x20)
+//         }
+//     }
 //     function allocateMemory(size) -> memPtr
 //     {
 //         memPtr := mload(64)