Merge pull request #9985 from ethereum/optimizeDeleteStructSol2Yul

[Sol->Yul] Optimizing delete struct.

test/libsolidity/semanticTests/structs/struct_delete_storage_nested_small.sol

@@ -0,0 +1,35 @@
+contract C {
+    struct S {
+        uint32 a;
+        S[] x;
+    }
+    S s;
+    function f() public returns (uint256 r1, uint256 r2, uint256 r3) {
+        assembly {
+            // 2 ** 150 - 1
+            sstore(s.slot, 1427247692705959881058285969449495136382746623)
+        }
+        s.a = 1;
+        s.x.push(); s.x.push();
+        S storage ptr1 = s.x[0];
+        S storage ptr2 = s.x[1];
+        assembly {
+            // 2 ** 150 - 1
+            sstore(ptr1.slot, 1427247692705959881058285969449495136382746623)
+            sstore(ptr2.slot, 1427247692705959881058285969449495136382746623)
+        }
+        s.x[0].a = 2; s.x[1].a = 3;
+        delete s;
+        assert(s.a == 0);
+        assert(s.x.length == 0);
+        assembly {
+            r1 := sload(s.slot)
+            r2 := sload(ptr1.slot)
+            r3 := sload(ptr2.slot)
+        }
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// f() -> 0, 0, 0

test/libsolidity/semanticTests/structs/struct_delete_storage_small.sol

@@ -0,0 +1,24 @@
+contract C {
+    struct S {
+        uint64 y;
+        uint64 z;
+    }
+    S s;
+    function f() public returns (uint256 ret) {
+        assembly {
+            // 2 ** 150 - 1
+            sstore(s.slot, 1427247692705959881058285969449495136382746623)
+        }
+        s.y = 1; s.z = 2;
+        delete s;
+        assert(s.y == 0);
+        assert(s.z == 0);
+        assembly {
+            ret := sload(s.slot)
+        }
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// f() -> 0

test/libsolidity/semanticTests/structs/struct_delete_storage_with_arrays_small.sol

@@ -0,0 +1,29 @@
+contract C {
+    struct S {
+        uint32 a;
+        uint32[3] b;
+        uint32[] x;
+    }
+    S s;
+    function f() public returns (uint256 ret) {
+        assembly {
+            // 2 ** 150 - 1
+            sstore(s.slot, 1427247692705959881058285969449495136382746623)
+        }
+        s.a = 1;
+        s.b[0] = 2; s.b[1] = 3;
+        s.x.push(4); s.x.push(5);
+        delete s;
+        assert(s.a == 0);
+        assert(s.b[0] == 0);
+        assert(s.b[1] == 0);
+        assert(s.x.length == 0);
+        assembly {
+            ret := sload(s.slot)
+        }
+    }
+}
+// ====
+// compileViaYul: true
+// ----
+// f() -> 0