Improved branch handling in data flow analyzer.

test/libyul/yulOptimizerTests/fullSuite/revert_in_switch.yul

@@ -0,0 +1,21 @@
+{
+    let x := 0
+    switch calldataload(0)
+    case 0 {
+        x := calldataload(99)
+    }
+    case 1 {
+        if 0 { revert(0, 0) }
+    }
+    sstore(0, x)
+}
+// ----
+// step: fullSuite
+//
+// {
+//     {
+//         let x := 0
+//         if iszero(calldataload(x)) { x := calldataload(99) }
+//         sstore(0, x)
+//     }
+// }

test/libyul/yulOptimizerTests/loadResolver/mload_with_revert.yul

@@ -0,0 +1,29 @@
+{
+    let b := mload(2)
+    mstore(0, b)
+    if calldataload(1) {
+        mstore(2, 7)
+        mstore(0, 7)
+        return(0, 0)
+    }
+    sstore(0, mload(0))
+}
+// ----
+// step: loadResolver
+//
+// {
+//     {
+//         let _1 := 2
+//         let b := mload(_1)
+//         let _2 := 0
+//         mstore(_2, b)
+//         if calldataload(1)
+//         {
+//             let _5 := 7
+//             mstore(_1, _5)
+//             mstore(_2, _5)
+//             return(_2, _2)
+//         }
+//         sstore(_2, b)
+//     }
+// }

test/libyul/yulOptimizerTests/rematerialiser/branches_switch.yul

@@ -16,7 +16,7 @@
 //     case 1 { b := 1 }
 //     default {
 //         let x := 1
-//         let y := b
+//         let y := 2
 //         b := 1
 //     }
 //     pop(add(1, b))