Use the type system to check if something is flowed out of (#1224)

now that the type system has a proper unreachable, we don't need obviouslyDoesNotFlowOut

2 files changed, 3 insertions, 15 deletions

diff --git a/src/ast_utils.h b/src/ast_utils.h
index dfa233f26..6e5251860 100644
--- a/src/ast_utils.h
+++ b/src/ast_utils.h
@@ -55,18 +55,6 @@ struct ExpressionAnalyzer {
     return !curr->condition && !curr->value;
   }
 
-  // Checks if an expression does not flow out in an obvious way.
-  // We return true if it cannot flow out. If it can flow out, we
-  // might still return true, as the analysis here is simple and fast.
-  static bool obviouslyDoesNotFlowOut(Expression* curr) {
-    if (auto* br = curr->dynCast<Break>()) {
-      if (!br->condition) return true;
-    } else if (auto* block = curr->dynCast<Block>()) {
-      if (block->list.size() > 0 && obviouslyDoesNotFlowOut(block->list.back()) && !BranchUtils::BranchSeeker::hasReachable(block, block->name)) return true;
-    }
-    return false;
-  }
-
   using ExprComparer = std::function<bool(Expression*, Expression*)>;
   static bool flexibleEqual(Expression* left, Expression* right, ExprComparer comparer);
 
diff --git a/src/passes/RemoveUnusedBrs.cpp b/src/passes/RemoveUnusedBrs.cpp
index 7903534b6..d2cdec7ad 100644
--- a/src/passes/RemoveUnusedBrs.cpp
+++ b/src/passes/RemoveUnusedBrs.cpp
@@ -250,7 +250,7 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> {
         // let's try to move the code going to the top of the loop into the if-else
         if (!iff->ifFalse) {
           // we need the ifTrue to break, so it cannot reach the code we want to move
-          if (ExpressionAnalyzer::obviouslyDoesNotFlowOut(iff->ifTrue)) {
+          if (iff->ifTrue->type == unreachable) {
             iff->ifFalse = builder.stealSlice(block, i + 1, list.size());
             iff->finalize();
             block->finalize();
@@ -288,12 +288,12 @@ struct RemoveUnusedBrs : public WalkerPass<PostWalker<RemoveUnusedBrs>> {
             return block;
           };
 
-          if (ExpressionAnalyzer::obviouslyDoesNotFlowOut(iff->ifTrue)) {
+          if (iff->ifTrue->type == unreachable) {
             iff->ifFalse = blockifyMerge(iff->ifFalse, builder.stealSlice(block, i + 1, list.size()));
             iff->finalize();
             block->finalize();
             return true;
-          } else if (ExpressionAnalyzer::obviouslyDoesNotFlowOut(iff->ifFalse)) {
+          } else if (iff->ifFalse->type == unreachable) {
             iff->ifTrue = blockifyMerge(iff->ifTrue, builder.stealSlice(block, i + 1, list.size()));
             iff->finalize();
             block->finalize();