wasm2js: optimize loops and eqz (#2051)

1 files changed, 10 insertions, 7 deletions

diff --git a/src/wasm2js.h b/src/wasm2js.h
index 84c65b189..fdfa77b84 100644
--- a/src/wasm2js.h
+++ b/src/wasm2js.h
@@ -823,9 +823,14 @@ Ref Wasm2JSBuilder::processFunctionBody(Module* m, Function* func, bool standalo
     Ref visitLoop(Loop* curr) {
       Name asmLabel = curr->name;
       continueLabels.insert(asmLabel);
-      Ref body = blockify(visit(curr->body, result));
-      flattenAppend(body, ValueBuilder::makeBreak(fromName(asmLabel, NameScope::Label)));
-      Ref ret = ValueBuilder::makeDo(body, ValueBuilder::makeInt(1));
+      Ref body = visit(curr->body, result);
+      // if we can reach the end of the block, we must leave the while (1) loop
+      if (curr->body->type != unreachable) {
+        assert(curr->body->type == none); // flat IR
+        body = blockify(body);
+        flattenAppend(body, ValueBuilder::makeBreak(fromName(asmLabel, NameScope::Label)));
+      }
+      Ref ret = ValueBuilder::makeWhile(ValueBuilder::makeInt(1), body);
       return ValueBuilder::makeLabel(fromName(asmLabel, NameScope::Label), ret);
     }
 
@@ -1207,10 +1212,8 @@ Ref Wasm2JSBuilder::processFunctionBody(Module* m, Function* func, bool standalo
                         << std::endl;
               WASM_UNREACHABLE();
             case EqZInt32:
-              return ValueBuilder::makeBinary(
-                  makeAsmCoercion(visit(curr->value,
-                                        EXPRESSION_RESULT), ASM_INT), EQ,
-                  makeAsmCoercion(ValueBuilder::makeInt(0), ASM_INT));
+              // XXX !x does change the type to bool, which is correct, but may be slower?
+              return ValueBuilder::makeUnary(L_NOT, visit(curr->value, EXPRESSION_RESULT));
             case ReinterpretFloat32: {
               ABI::wasm2js::ensureScratchMemoryHelpers(module, ABI::wasm2js::SCRATCH_STORE_F32);
               ABI::wasm2js::ensureScratchMemoryHelpers(module, ABI::wasm2js::SCRATCH_LOAD_I32);