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, 3 deletions

diff --git a/test/lit/passes/optimize-instructions-gc-iit.wast b/test/lit/passes/optimize-instructions-gc-iit.wast
index 3f0c926d3..24c5c6809 100644
--- a/test/lit/passes/optimize-instructions-gc-iit.wast
+++ b/test/lit/passes/optimize-instructions-gc-iit.wast
@@ -132,7 +132,7 @@
 
   ;; CHECK:      (func $ref-cast-iit-bad (param $parent (ref $parent))
   ;; CHECK-NEXT:  (drop
-  ;; CHECK-NEXT:   (block $block (result (ref $parent))
+  ;; CHECK-NEXT:   (block (result (ref $parent))
   ;; CHECK-NEXT:    (call $foo)
   ;; CHECK-NEXT:    (local.get $parent)
   ;; CHECK-NEXT:   )
@@ -145,7 +145,7 @@
   ;; CHECK-NEXT: )
   ;; NOMNL:      (func $ref-cast-iit-bad (type $ref|$parent|_=>_none) (param $parent (ref $parent))
   ;; NOMNL-NEXT:  (drop
-  ;; NOMNL-NEXT:   (block $block (result (ref $parent))
+  ;; NOMNL-NEXT:   (block (result (ref $parent))
   ;; NOMNL-NEXT:    (call $foo)
   ;; NOMNL-NEXT:    (local.get $parent)
   ;; NOMNL-NEXT:   )
@@ -158,7 +158,7 @@
   ;; NOMNL-NEXT: )
   ;; NOMNL-TNH:      (func $ref-cast-iit-bad (type $ref|$parent|_=>_none) (param $parent (ref $parent))
   ;; NOMNL-TNH-NEXT:  (drop
-  ;; NOMNL-TNH-NEXT:   (block $block (result (ref $parent))
+  ;; NOMNL-TNH-NEXT:   (block (result (ref $parent))
   ;; NOMNL-TNH-NEXT:    (call $foo)
   ;; NOMNL-TNH-NEXT:    (local.get $parent)
   ;; NOMNL-TNH-NEXT:   )