hrkrshnn

Optimized IR:
/*******************************************************
 ,*                       WARNING                       *
 ,*  Solidity to Yul compilation is still EXPERIMENTAL  *
 ,*       It can result in LOSS OF FUNDS or worse       *
 ,*                !USE AT YOUR OWN RISK!               *
 ,*******************************************************/

object "C_164" {
    code {

hrkrshnn

from rule import Rule
from opcodes import *

rule = Rule()

for i in range(1, 25):
    X = BitVec('X', 8*i)
    Y = BitVec('Y', 8*i)
    max = 2**(8*i) - 1
    rule.check(

hrkrshnn

{
    {
        mstore(64, memoryguard(0x0120))
        if iszero(lt(calldatasize(), 4))
        {
            switch shift_right_224_unsigned(calldataload(0))
            case 0x13d1aa2e {
                let param_0, param_1 := abi_decode_tuple_t_uint256t_uint256(4, calldatasize())
                let ret_0 := fun_f_23(param_0, param_1)
                let memPos := allocateMemory(0)

hrkrshnn

#include <iostream>
#include <optional>

struct A
{
    A() { }
    A(A const& a) { std::cout << "move construction failed!\n"; }
    A(A&& o) { std::cout << "moved construction worked!\n"; }
    A& operator=(A const& other) {
        std::cout << "move assignment failed!\n";

hrkrshnn

When you're looping over an array from front to back, does it make sense to cache arr.length in a stack variable, or will it SLOAD/MLOAD that only once if it sees it won't change in the loop body

In the Yul optimizer (for the new code generator), there is an optimization step LoopInvariantCodeMotion designed to detect expressions that remain invariant in the loop and move them outside the loop. Take the following solidity example that finds the sum of a dynamic integer array in storage.

        uint sum = 0;
        for (uint i = 0; i < arr.length; ++i)
        {
            sum += arr[i];
 }

hrkrshnn

modified   test/libyul/YulOptimizerTest.cpp
@@ -300,17 +300,17 @@ TestCase::TestResult YulOptimizerTest::run(ostream& _stream, string const& _line
 	}
 	else if (m_optimizerStep == "loadResolver")
 	{
-		disambiguate();
-		ForLoopInitRewriter::run(*m_context, *m_object->code);
-		ExpressionSplitter::run(*m_context, *m_object->code);
-		CommonSubexpressionEliminator::run(*m_context, *m_object->code);
-		ExpressionSimplifier::run(*m_context, *m_object->code);

hrkrshnn

0	0	0	- 1	-1
3	1	-1	1	0
3	1	1	0	1

Fix the first column

6	2	0	0	0
3	1	-1	1	0

hrkrshnn

{
    let _2296 := 128
    let _2297 := 64
    mstore(_2297, _2296)
    let _4 := calldatasize()
    let _2298 := 4
    let _2299 := lt(_4, _2298)
    let _2300 := iszero(_2299)
    if _2300
    {

hrkrshnn

pragma experimental SMTChecker;

contract A {
	int public x;
	event Ee(string);
	function f() public virtual {
		x = 1;
		emit Ee(type(A).name);
	}
}

hrkrshnn

diff -u /tmp/old.txt /tmp/new.txt
--- /tmp/old.txt	2021-02-01 20:13:33.637282924 +0100
+++ /tmp/new.txt	2021-02-01 20:14:02.415177046 +0100
@@ -1,7 +1,7 @@
 
-======= <stdin>:C =======
+======= optimizer_inliner_inc/input.sol:C =======
 EVM assembly:
-    /* "<stdin>":157:279  contract C {... */
+    /* "optimizer_inliner_inc/input.sol":157:279  contract C {... */