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, 3 insertions, 5 deletions

diff --git a/test/passes/ssa_fuzz-exec_enable-threads.txt b/test/passes/ssa_fuzz-exec_enable-threads.txt
index 40845e209..6334b35a7 100644
--- a/test/passes/ssa_fuzz-exec_enable-threads.txt
+++ b/test/passes/ssa_fuzz-exec_enable-threads.txt
@@ -54,7 +54,7 @@
            )
            (i32.const 1)
           )
-          (block $block (result i32)
+          (block (result i32)
            (loop $label$15
             (if
              (i32.const 0)
@@ -70,10 +70,8 @@
                )
               )
              )
-             (block $block4
-              (br_if $label$15
-               (i32.const 0)
-              )
+             (br_if $label$15
+              (i32.const 0)
              )
             )
             (br_if $label$15