Avoid adding new unneeded names to blocks in text roundtripping (#4943)

Previously the wat parser would turn this input:

(block
  (nop)
)

into something like this:

(block $block17
  (nop)
)

It just added a name all the time, in case the block is referred to by an index
later even though it doesn't have a name.

This PR makes us rountrip more precisely by not adding such names: if there
was no name before, and there is no break by index, then do not add a name.

In addition, this will be useful for non-nullable locals since whether a block has
a name or not matters there. Like #4912, this makes us more regular in our
usage of block names.

1 files changed, 5 insertions, 7 deletions

diff --git a/test/wasm2js/f32.2asm.js b/test/wasm2js/f32.2asm.js
index 66c0b9334..bc4c387a2 100644
--- a/test/wasm2js/f32.2asm.js
+++ b/test/wasm2js/f32.2asm.js
@@ -80,14 +80,12 @@ function asmFunc(env) {
   var$1 = Math_fround(Math_floor(var$0));
   var$2 = Math_fround(var$0 - var$1);
   if (!(var$2 < Math_fround(.5))) {
-   block : {
-    var$0 = Math_fround(Math_ceil(var$0));
-    if (var$2 > Math_fround(.5)) {
-     return Math_fround(var$0)
-    }
-    var$2 = Math_fround(var$1 * Math_fround(.5));
-    var$1 = Math_fround(var$2 - Math_fround(Math_floor(var$2))) == Math_fround(0.0) ? var$1 : var$0;
+   var$0 = Math_fround(Math_ceil(var$0));
+   if (var$2 > Math_fround(.5)) {
+    return Math_fround(var$0)
    }
+   var$2 = Math_fround(var$1 * Math_fround(.5));
+   var$1 = Math_fround(var$2 - Math_fround(Math_floor(var$2))) == Math_fround(0.0) ? var$1 : var$0;
   }
   return Math_fround(var$1);
  }