finalize in remove-unused-brs when we conditionalize a br - we may have put an if at the end of a block, and if the block if is typed, then so now must be the if (it must have both arms of unreachable type, so this is ok to do)

Author: kripken

src/passes/RemoveUnusedBrs.cpp

@@ -219,6 +219,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
           // we need the ifTrue to break, so it cannot reach the code we want to move
           if (ExpressionAnalyzer::obviouslyDoesNotFlowOut(iff->ifTrue)) {
             iff->ifFalse = builder.stealSlice(block, i + 1, list.size());
+            block->finalize(block->type);
             return true;
           }
         } else {
@@ -227,9 +228,11 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
           assert(!isConcreteWasmType(iff->type)); // can't be, since in the middle of a block
           if (ExpressionAnalyzer::obviouslyDoesNotFlowOut(iff->ifTrue)) {
             iff->ifFalse = builder.blockifyMerge(iff->ifFalse, builder.stealSlice(block, i + 1, list.size()));
+            block->finalize(block->type);
             return true;
           } else if (ExpressionAnalyzer::obviouslyDoesNotFlowOut(iff->ifFalse)) {
             iff->ifTrue = builder.blockifyMerge(iff->ifTrue, builder.stealSlice(block, i + 1, list.size()));
+            block->finalize(block->type);
             return true;
           }
         }
@@ -256,6 +259,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs, Visitor<R
               // note that we could drop the last element here, it is a br we know for sure is removable,
               // but telling stealSlice to steal all to the end is more efficient, it can just truncate.
               list[i] = builder.makeIf(brIf->condition, builder.makeBreak(brIf->name), builder.stealSlice(block, i + 1, list.size()));
+              block->finalize(block->type);
               return true;
             }
           }

test/passes/remove-unused-brs.txt

@@ -937,4 +937,22 @@
       )
     )
   )
+  (func $loop-if (type $2) (result i32)
+    (block $outer i32
+      (loop $typed i32
+        (if i32
+          (i32.const 2)
+          (block $block i32
+            (drop
+              (call $loop-if)
+            )
+            (br $outer
+              (i32.const 0)
+            )
+          )
+          (br $typed)
+        )
+      )
+    )
+  )
 )

test/passes/remove-unused-brs.wast

@@ -831,5 +831,21 @@
       )
     )
   )
+  (func $loop-if (result i32)
+    (block $outer i32
+      (loop $typed i32
+        ;; we can move the br after us into our if-else, but that then means we are the final
+        ;; element in the block, and so must be typed
+        (if
+          (i32.const 2)
+          (block
+            (drop (call $loop-if))
+            (br $outer (i32.const 0))
+          )
+        )
+        (br $typed)
+      )
+    )
+  )
 )