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, 64 insertions, 72 deletions

diff --git a/test/wasm2js/stack-modified.2asm.js b/test/wasm2js/stack-modified.2asm.js
index 3b5ed595a..26b8bc26b 100644
--- a/test/wasm2js/stack-modified.2asm.js
+++ b/test/wasm2js/stack-modified.2asm.js
@@ -82,24 +82,22 @@ function asmFunc(env) {
     if ((i64toi32_i32$2 | 0) == (i64toi32_i32$3 | 0) & (i64toi32_i32$0 | 0) == (i64toi32_i32$1 | 0) | 0) {
      break label$1
     } else {
-     block : {
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$2 = var$2$hi;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$0 = var$2$hi;
-      i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
-      i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
-      var$2 = i64toi32_i32$0;
-      var$2$hi = i64toi32_i32$2;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$3 = var$1;
-      i64toi32_i32$0 = 0;
-      i64toi32_i32$1 = 1;
-      i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
-      i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
-      var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
-      var$1$hi = i64toi32_i32$5;
-     }
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$2 = var$2$hi;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$0 = var$2$hi;
+     i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
+     i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
+     var$2 = i64toi32_i32$0;
+     var$2$hi = i64toi32_i32$2;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$3 = var$1;
+     i64toi32_i32$0 = 0;
+     i64toi32_i32$1 = 1;
+     i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
+     i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
+     var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
+     var$1$hi = i64toi32_i32$5;
     }
     continue label$2;
    };
@@ -129,24 +127,22 @@ function asmFunc(env) {
     if ((i64toi32_i32$2 | 0) == (i64toi32_i32$3 | 0) & (i64toi32_i32$0 | 0) == (i64toi32_i32$1 | 0) | 0) {
      break label$1
     } else {
-     block : {
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$2 = var$2$hi;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$0 = var$2$hi;
-      i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
-      i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
-      var$2 = i64toi32_i32$0;
-      var$2$hi = i64toi32_i32$2;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$3 = var$1;
-      i64toi32_i32$0 = 0;
-      i64toi32_i32$1 = 1;
-      i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
-      i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
-      var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
-      var$1$hi = i64toi32_i32$5;
-     }
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$2 = var$2$hi;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$0 = var$2$hi;
+     i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
+     i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
+     var$2 = i64toi32_i32$0;
+     var$2$hi = i64toi32_i32$2;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$3 = var$1;
+     i64toi32_i32$0 = 0;
+     i64toi32_i32$1 = 1;
+     i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
+     i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
+     var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
+     var$1$hi = i64toi32_i32$5;
     }
     continue label$2;
    };
@@ -176,24 +172,22 @@ function asmFunc(env) {
     if ((i64toi32_i32$2 | 0) == (i64toi32_i32$3 | 0) & (i64toi32_i32$0 | 0) == (i64toi32_i32$1 | 0) | 0) {
      break label$1
     } else {
-     block : {
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$2 = var$2$hi;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$0 = var$2$hi;
-      i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
-      i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
-      var$2 = i64toi32_i32$0;
-      var$2$hi = i64toi32_i32$2;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$3 = var$1;
-      i64toi32_i32$0 = 0;
-      i64toi32_i32$1 = 1;
-      i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
-      i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
-      var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
-      var$1$hi = i64toi32_i32$5;
-     }
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$2 = var$2$hi;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$0 = var$2$hi;
+     i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
+     i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
+     var$2 = i64toi32_i32$0;
+     var$2$hi = i64toi32_i32$2;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$3 = var$1;
+     i64toi32_i32$0 = 0;
+     i64toi32_i32$1 = 1;
+     i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
+     i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
+     var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
+     var$1$hi = i64toi32_i32$5;
     }
     continue label$2;
    };
@@ -223,24 +217,22 @@ function asmFunc(env) {
     if ((i64toi32_i32$2 | 0) == (i64toi32_i32$3 | 0) & (i64toi32_i32$0 | 0) == (i64toi32_i32$1 | 0) | 0) {
      break label$1
     } else {
-     block : {
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$2 = var$2$hi;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$0 = var$2$hi;
-      i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
-      i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
-      var$2 = i64toi32_i32$0;
-      var$2$hi = i64toi32_i32$2;
-      i64toi32_i32$2 = var$1$hi;
-      i64toi32_i32$3 = var$1;
-      i64toi32_i32$0 = 0;
-      i64toi32_i32$1 = 1;
-      i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
-      i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
-      var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
-      var$1$hi = i64toi32_i32$5;
-     }
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$2 = var$2$hi;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$0 = var$2$hi;
+     i64toi32_i32$0 = __wasm_i64_mul(var$1 | 0, i64toi32_i32$2 | 0, var$2 | 0, i64toi32_i32$0 | 0) | 0;
+     i64toi32_i32$2 = i64toi32_i32$HIGH_BITS;
+     var$2 = i64toi32_i32$0;
+     var$2$hi = i64toi32_i32$2;
+     i64toi32_i32$2 = var$1$hi;
+     i64toi32_i32$3 = var$1;
+     i64toi32_i32$0 = 0;
+     i64toi32_i32$1 = 1;
+     i64toi32_i32$5 = (i64toi32_i32$3 >>> 0 < i64toi32_i32$1 >>> 0) + i64toi32_i32$0 | 0;
+     i64toi32_i32$5 = i64toi32_i32$2 - i64toi32_i32$5 | 0;
+     var$1 = i64toi32_i32$3 - i64toi32_i32$1 | 0;
+     var$1$hi = i64toi32_i32$5;
     }
     continue label$2;
    };