[NFC] Finalize blocks with explicit breakability in IRBuilder (#7085)

Since IRBuilder already knows what labels are used by branches, it is
easy for it to pass that information when finalizing blocks. This avoids
finalization having to walk the blocks looking for branches, speeding up
a future version of the binary parser that uses IRBuilder by 10%.

2 files changed, 16 insertions, 4 deletions

diff --git a/src/passes/Outlining.cpp b/src/passes/Outlining.cpp
index 429511557..b86e6cd17 100644
--- a/src/passes/Outlining.cpp
+++ b/src/passes/Outlining.cpp
@@ -304,6 +304,14 @@ struct Outlining : public Pass {
     // Position the outlined functions first in the functions vector to make
     // the outlining lit tests far more readable.
     moveOutlinedFunctions(module, substrings.size());
+
+    // Because we visit control flow in stringified order rather than normal
+    // postorder, IRBuilder is not able to properly track branches, so it may
+    // not have finalized blocks with the correct types. ReFinalize now to fix
+    // any issues.
+    PassRunner runner(getPassRunner());
+    runner.add(std::make_unique<ReFinalize>());
+    runner.run();
   }
 
   Name addOutlinedFunction(Module* module,
diff --git a/src/wasm/wasm-ir-builder.cpp b/src/wasm/wasm-ir-builder.cpp
index 0d46156be..5253c91ee 100644
--- a/src/wasm/wasm-ir-builder.cpp
+++ b/src/wasm/wasm-ir-builder.cpp
@@ -972,7 +972,12 @@ Result<> IRBuilder::visitEnd() {
       block->type = blockType;
       return block;
     }
-    return builder.makeBlock(label, {curr}, blockType);
+    auto* block = builder.makeBlock();
+    block->name = label;
+    block->list.push_back(curr);
+    block->finalize(blockType,
+                    scope.labelUsed ? Block::HasBreak : Block::NoBreak);
+    return block;
   };
 
   if (auto* func = scope.getFunction()) {
@@ -985,9 +990,8 @@ Result<> IRBuilder::visitEnd() {
   } else if (auto* block = scope.getBlock()) {
     assert(*expr == block);
     block->name = scope.label;
-    // TODO: Track branches so we can know whether this block is a target and
-    // finalize more efficiently.
-    block->finalize(block->type);
+    block->finalize(block->type,
+                    scope.labelUsed ? Block::HasBreak : Block::NoBreak);
     push(block);
   } else if (auto* loop = scope.getLoop()) {
     loop->body = *expr;