[YulOpt] Implement loop-invariant code motion

test/libyul/yulOptimizerTests/loopInvariantCodeMotion/dependOnVarInLoop.yul

@@ -0,0 +1,23 @@
+{
+  let b := 1
+  for { let a := 1 } iszero(eq(a, 10)) { a := add(a, 1) } {
+    let c := mload(3)    // c cannot be moved because non-movable
+    let not_inv := add(b, c) // no_inv cannot be moved because its value depends on c
+    a := add(a, 1)
+    mstore(a, not_inv)
+  }
+}
+// ====
+// step: loopInvariantCodeMotion
+// ----
+// {
+//     let b := 1
+//     let a := 1
+//     for { } iszero(eq(a, 10)) { a := add(a, 1) }
+//     {
+//         let c := mload(3)
+//         let not_inv := add(b, c)
+//         a := add(a, 1)
+//         mstore(a, not_inv)
+//     }
+// }

test/libyul/yulOptimizerTests/loopInvariantCodeMotion/multi.yul

@@ -0,0 +1,26 @@
+{
+  let b := 1
+  // tests if c, d, and inv can be moved outside in single pass
+  for { let a := 1 } iszero(eq(a, 10)) { a := add(a, 1) } {
+    let c := b
+    let d := mul(c, 2)
+    let inv := add(c, d)
+    a := add(a, 1)
+    mstore(a, inv)
+  }
+}
+// ====
+// step: loopInvariantCodeMotion
+// ----
+// {
+//     let b := 1
+//     let a := 1
+//     let c := b
+//     let d := mul(c, 2)
+//     let inv := add(c, d)
+//     for { } iszero(eq(a, 10)) { a := add(a, 1) }
+//     {
+//         a := add(a, 1)
+//         mstore(a, inv)
+//     }
+// }

test/libyul/yulOptimizerTests/loopInvariantCodeMotion/non-ssavar.yul

@@ -0,0 +1,23 @@
+{
+  let b := 1
+  for { let a := 1 } iszero(eq(a, 10)) { a := add(a, 1) } {
+    let not_inv := add(b, 42)
+    not_inv := add(not_inv, 1)
+    a := add(a, 1)
+    mstore(a, not_inv)
+  }
+}
+// ====
+// step: loopInvariantCodeMotion
+// ----
+// {
+//     let b := 1
+//     let a := 1
+//     for { } iszero(eq(a, 10)) { a := add(a, 1) }
+//     {
+//         let not_inv := add(b, 42)
+//         not_inv := add(not_inv, 1)
+//         a := add(a, 1)
+//         mstore(a, not_inv)
+//     }
+// }

test/libyul/yulOptimizerTests/loopInvariantCodeMotion/nonMovable.yul

@@ -0,0 +1,21 @@
+{
+  let b := 0
+  for { let a := 1 } iszero(eq(a, 10)) { a := add(a, 1) } {
+    let inv := mload(b)
+    a := add(a, 1)
+    mstore(a, inv)
+  }
+}
+// ====
+// step: loopInvariantCodeMotion
+// ----
+// {
+//     let b := 0
+//     let a := 1
+//     for { } iszero(eq(a, 10)) { a := add(a, 1) }
+//     {
+//         let inv := mload(b)
+//         a := add(a, 1)
+//         mstore(a, inv)
+//     }
+// }

test/libyul/yulOptimizerTests/loopInvariantCodeMotion/recursive.yul

@@ -0,0 +1,25 @@
+{
+  let b := 1
+  for { let a := 1 } iszero(eq(a, 10)) { a := add(a, 1) } {
+    for { let a2 := 1 } iszero(eq(a2, 10)) { a2 := add(a2, 1) } {
+      let inv := add(b, 42)
+      mstore(a, inv)
+    }
+    a := add(a, 1)
+  }
+}
+// ====
+// step: loopInvariantCodeMotion
+// ----
+// {
+//     let b := 1
+//     let a := 1
+//     let inv := add(b, 42)
+//     for { } iszero(eq(a, 10)) { a := add(a, 1) }
+//     {
+//         let a2 := 1
+//         for { } iszero(eq(a2, 10)) { a2 := add(a2, 1) }
+//         { mstore(a, inv) }
+//         a := add(a, 1)
+//     }
+// }

test/libyul/yulOptimizerTests/loopInvariantCodeMotion/simple.yul

@@ -0,0 +1,21 @@
+{
+  let b := 1
+  for { let a := 1 } iszero(eq(a, 10)) { a := add(a, 1) } {
+    let inv := add(b, 42)
+    a := add(a, 1)
+    mstore(a, inv)
+  }
+}
+// ====
+// step: loopInvariantCodeMotion
+// ----
+// {
+//     let b := 1
+//     let a := 1
+//     let inv := add(b, 42)
+//     for { } iszero(eq(a, 10)) { a := add(a, 1) }
+//     {
+//         a := add(a, 1)
+//         mstore(a, inv)
+//     }
+// }