From f3125579cca998300c230232ed4ded4fe0aaa34c Mon Sep 17 00:00:00 2001
From: Alon Zakai <azakai@google.com>
Date: Mon, 26 Oct 2020 18:43:29 -0700
Subject: Rewrite DCE pass (#3274)

The DCE pass is one of the oldest in binaryen, and had quite a lot of
cruft from the changes in unreachability and other stuff in wasm and
binaryen's history. This PR rewrites it from scratch, making it about
1/3 the size.

I noticed this when looking for places to use code autogeneration.
The old version had annoying boilerplate, while the new one avoids
any need for it.

There may be noticeable differences, as the old pass did more than
it needed to. It overlapped with remove-unused-names for some
reason I don't remember. The new pass leaves that to the other
pass to do. I added another run of remove-unused-names to avoid
noticeable differences in optimized builds, but you can see
differences in the testcases that only run DCE by itself. (The test
differences in this PR are mostly whitespace.)

(The overlap is that if a block ended up not needed, that is, all
branches to it were removed, the old DCE would remove the block.)

This pass is about 15% faster than the old version. However, when
adding another run of remove-unused-names the difference
basically vanishes, so this isn't a speedup.
---
 test/passes/asyncify_enable-multivalue.txt         | 408 +++++++++++----------
 ...syncify_mod-asyncify-always-and-only-unwind.txt |  74 ++--
 test/passes/asyncify_mod-asyncify-never-unwind.txt |  76 ++--
 ...arg=asyncify-imports@env.import,env.import2.txt | 252 +++++++------
 test/passes/dce_all-features.txt                   | 243 ++++++++----
 test/passes/dce_all-features.wast                  |  57 +++
 test/passes/dce_vacuum.bin.txt                     |  98 -----
 test/passes/dce_vacuum.txt                         |  25 --
 test/passes/dce_vacuum.wasm                        | Bin 260 -> 0 bytes
 test/passes/dce_vacuum.wast                        |  51 ---
 test/passes/dce_vacuum_remove-unused-names.bin.txt |  94 +++++
 test/passes/dce_vacuum_remove-unused-names.txt     |  25 ++
 test/passes/dce_vacuum_remove-unused-names.wasm    | Bin 0 -> 260 bytes
 test/passes/dce_vacuum_remove-unused-names.wast    |  51 +++
 test/passes/interesting-pass-mix.txt               |  19 +-
 test/wasm2js/br.2asm.js                            |  22 +-
 test/wasm2js/br_table.2asm.js                      |  34 +-
 test/wasm2js/br_table_temp.2asm.js                 |  34 +-
 test/wasm2js/excess_fallthrough.2asm.js            |  28 +-
 19 files changed, 893 insertions(+), 698 deletions(-)
 delete mode 100644 test/passes/dce_vacuum.bin.txt
 delete mode 100644 test/passes/dce_vacuum.txt
 delete mode 100644 test/passes/dce_vacuum.wasm
 delete mode 100644 test/passes/dce_vacuum.wast
 create mode 100644 test/passes/dce_vacuum_remove-unused-names.bin.txt
 create mode 100644 test/passes/dce_vacuum_remove-unused-names.txt
 create mode 100644 test/passes/dce_vacuum_remove-unused-names.wasm
 create mode 100644 test/passes/dce_vacuum_remove-unused-names.wast

(limited to 'test')

diff --git a/test/passes/asyncify_enable-multivalue.txt b/test/passes/asyncify_enable-multivalue.txt
index 08d0d7bf9..7d92b0c97 100644
--- a/test/passes/asyncify_enable-multivalue.txt
+++ b/test/passes/asyncify_enable-multivalue.txt
@@ -491,55 +491,57 @@
        )
       )
       (block
-       (if
-        (if (result i32)
-         (i32.eq
-          (global.get $__asyncify_state)
-          (i32.const 0)
-         )
-         (i32.const 1)
-         (i32.eq
-          (local.get $6)
-          (i32.const 0)
-         )
-        )
-        (block
-         (local.set $7
-          (call $import2)
-         )
-         (if
+       (block
+        (if
+         (if (result i32)
           (i32.eq
            (global.get $__asyncify_state)
-           (i32.const 1)
+           (i32.const 0)
           )
-          (br $__asyncify_unwind
+          (i32.const 1)
+          (i32.eq
+           (local.get $6)
            (i32.const 0)
           )
-          (local.set $1
-           (local.get $7)
+         )
+         (block
+          (local.set $7
+           (call $import2)
+          )
+          (if
+           (i32.eq
+            (global.get $__asyncify_state)
+            (i32.const 1)
+           )
+           (br $__asyncify_unwind
+            (i32.const 0)
+           )
+           (local.set $1
+            (local.get $7)
+           )
           )
          )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (block
-         (local.set $temp
-          (local.get $1)
-         )
-         (local.set $2
-          (local.get $temp)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
          )
-         (return
-          (local.get $2)
+         (block
+          (local.set $temp
+           (local.get $1)
+          )
+          (local.set $2
+           (local.get $temp)
+          )
+          (return
+           (local.get $2)
+          )
          )
         )
+        (nop)
+        (nop)
        )
-       (nop)
-       (nop)
       )
       (unreachable)
      )
@@ -814,84 +816,86 @@
        )
       )
       (block
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (loop $l
-         (local.set $3
-          (local.get $y)
-         )
-         (local.set $4
-          (i32.add
-           (local.get $3)
-           (i32.const 1)
-          )
-         )
-         (local.set $x
-          (local.get $4)
-         )
-         (local.set $5
-          (local.get $x)
-         )
-         (local.set $6
-          (i32.div_s
-           (local.get $5)
-           (i32.const 3)
-          )
-         )
-         (local.set $y
-          (local.get $6)
-         )
-         (local.set $7
-          (local.get $y)
-         )
-         (br_if $l
-          (local.get $7)
-         )
-        )
-       )
-       (if
-        (if (result i32)
+       (block
+        (if
          (i32.eq
           (global.get $__asyncify_state)
           (i32.const 0)
          )
-         (i32.const 1)
-         (i32.eq
-          (local.get $12)
-          (i32.const 0)
+         (loop $l
+          (local.set $3
+           (local.get $y)
+          )
+          (local.set $4
+           (i32.add
+            (local.get $3)
+            (i32.const 1)
+           )
+          )
+          (local.set $x
+           (local.get $4)
+          )
+          (local.set $5
+           (local.get $x)
+          )
+          (local.set $6
+           (i32.div_s
+            (local.get $5)
+            (i32.const 3)
+           )
+          )
+          (local.set $y
+           (local.get $6)
+          )
+          (local.set $7
+           (local.get $y)
+          )
+          (br_if $l
+           (local.get $7)
+          )
          )
         )
-        (block
-         (call $import)
-         (if
+        (if
+         (if (result i32)
           (i32.eq
            (global.get $__asyncify_state)
-           (i32.const 1)
+           (i32.const 0)
           )
-          (br $__asyncify_unwind
+          (i32.const 1)
+          (i32.eq
+           (local.get $12)
            (i32.const 0)
           )
          )
+         (block
+          (call $import)
+          (if
+           (i32.eq
+            (global.get $__asyncify_state)
+            (i32.const 1)
+           )
+           (br $__asyncify_unwind
+            (i32.const 0)
+           )
+          )
+         )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (block
-         (local.set $8
-          (local.get $y)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
          )
-         (return
-          (local.get $8)
+         (block
+          (local.set $8
+           (local.get $y)
+          )
+          (return
+           (local.get $8)
+          )
          )
         )
+        (nop)
        )
-       (nop)
       )
       (unreachable)
      )
@@ -1291,90 +1295,92 @@
       )
       (block
        (block
-        (if
-         (i32.eq
-          (global.get $__asyncify_state)
-          (i32.const 0)
-         )
-         (local.set $1
-          (local.get $x)
-         )
-        )
         (block
          (if
           (i32.eq
            (global.get $__asyncify_state)
            (i32.const 0)
           )
-          (local.set $4
-           (local.get $1)
+          (local.set $1
+           (local.get $x)
           )
          )
-         (if
-          (i32.or
-           (local.get $4)
-           (i32.eq
-            (global.get $__asyncify_state)
-            (i32.const 2)
-           )
-          )
+         (block
           (if
            (i32.eq
             (global.get $__asyncify_state)
             (i32.const 0)
            )
-           (return
-            (i32.const 1)
-           )
-          )
-         )
-         (if
-          (i32.or
-           (i32.eqz
-            (local.get $4)
-           )
-           (i32.eq
-            (global.get $__asyncify_state)
-            (i32.const 2)
+           (local.set $4
+            (local.get $1)
            )
           )
           (if
-           (if (result i32)
+           (i32.or
+            (local.get $4)
             (i32.eq
              (global.get $__asyncify_state)
-             (i32.const 0)
+             (i32.const 2)
             )
-            (i32.const 1)
+           )
+           (if
             (i32.eq
-             (local.get $6)
+             (global.get $__asyncify_state)
              (i32.const 0)
             )
+            (return
+             (i32.const 1)
+            )
            )
-           (block
-            (call $import3
+          )
+          (if
+           (i32.or
+            (i32.eqz
+             (local.get $4)
+            )
+            (i32.eq
+             (global.get $__asyncify_state)
              (i32.const 2)
             )
-            (if
+           )
+           (if
+            (if (result i32)
              (i32.eq
               (global.get $__asyncify_state)
-              (i32.const 1)
+              (i32.const 0)
              )
-             (br $__asyncify_unwind
+             (i32.const 1)
+             (i32.eq
+              (local.get $6)
               (i32.const 0)
              )
             )
+            (block
+             (call $import3
+              (i32.const 2)
+             )
+             (if
+              (i32.eq
+               (global.get $__asyncify_state)
+               (i32.const 1)
+              )
+              (br $__asyncify_unwind
+               (i32.const 0)
+              )
+             )
+            )
            )
           )
          )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (return
-         (i32.const 3)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
+         )
+         (return
+          (i32.const 3)
+         )
         )
        )
       )
@@ -1470,90 +1476,92 @@
       )
       (block
        (block
-        (if
-         (i32.eq
-          (global.get $__asyncify_state)
-          (i32.const 0)
-         )
-         (local.set $1
-          (local.get $x)
-         )
-        )
         (block
          (if
           (i32.eq
            (global.get $__asyncify_state)
            (i32.const 0)
           )
-          (local.set $4
-           (local.get $1)
+          (local.set $1
+           (local.get $x)
           )
          )
-         (if
-          (i32.or
-           (local.get $4)
+         (block
+          (if
            (i32.eq
             (global.get $__asyncify_state)
-            (i32.const 2)
+            (i32.const 0)
+           )
+           (local.set $4
+            (local.get $1)
            )
           )
           (if
-           (if (result i32)
+           (i32.or
+            (local.get $4)
             (i32.eq
              (global.get $__asyncify_state)
-             (i32.const 0)
-            )
-            (i32.const 1)
-            (i32.eq
-             (local.get $6)
-             (i32.const 0)
+             (i32.const 2)
             )
            )
-           (block
-            (call $import3
-             (i32.const 1)
-            )
-            (if
+           (if
+            (if (result i32)
              (i32.eq
               (global.get $__asyncify_state)
-              (i32.const 1)
+              (i32.const 0)
              )
-             (br $__asyncify_unwind
+             (i32.const 1)
+             (i32.eq
+              (local.get $6)
               (i32.const 0)
              )
             )
-           )
-          )
-         )
-         (if
-          (i32.or
-           (i32.eqz
-            (local.get $4)
-           )
-           (i32.eq
-            (global.get $__asyncify_state)
-            (i32.const 2)
+            (block
+             (call $import3
+              (i32.const 1)
+             )
+             (if
+              (i32.eq
+               (global.get $__asyncify_state)
+               (i32.const 1)
+              )
+              (br $__asyncify_unwind
+               (i32.const 0)
+              )
+             )
+            )
            )
           )
           (if
-           (i32.eq
-            (global.get $__asyncify_state)
-            (i32.const 0)
+           (i32.or
+            (i32.eqz
+             (local.get $4)
+            )
+            (i32.eq
+             (global.get $__asyncify_state)
+             (i32.const 2)
+            )
            )
-           (return
-            (i32.const 2)
+           (if
+            (i32.eq
+             (global.get $__asyncify_state)
+             (i32.const 0)
+            )
+            (return
+             (i32.const 2)
+            )
            )
           )
          )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (return
-         (i32.const 3)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
+         )
+         (return
+          (i32.const 3)
+         )
         )
        )
       )
diff --git a/test/passes/asyncify_mod-asyncify-always-and-only-unwind.txt b/test/passes/asyncify_mod-asyncify-always-and-only-unwind.txt
index 62c3ba33f..ecf0a41c8 100644
--- a/test/passes/asyncify_mod-asyncify-always-and-only-unwind.txt
+++ b/test/passes/asyncify_mod-asyncify-always-and-only-unwind.txt
@@ -152,52 +152,54 @@
        )
       )
       (block
-       (if
-        (if (result i32)
-         (i32.eq
-          (global.get $__asyncify_state)
-          (i32.const 0)
-         )
-         (i32.const 1)
-         (i32.eq
-          (local.get $6)
-          (i32.const 0)
-         )
-        )
-        (block
-         (local.set $7
-          (call $import2)
-         )
-         (if
+       (block
+        (if
+         (if (result i32)
+          (i32.eq
+           (global.get $__asyncify_state)
+           (i32.const 0)
+          )
           (i32.const 1)
-          (br $__asyncify_unwind
+          (i32.eq
+           (local.get $6)
            (i32.const 0)
           )
-          (local.set $1
-           (local.get $7)
+         )
+         (block
+          (local.set $7
+           (call $import2)
+          )
+          (if
+           (i32.const 1)
+           (br $__asyncify_unwind
+            (i32.const 0)
+           )
+           (local.set $1
+            (local.get $7)
+           )
           )
          )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (block
-         (local.set $temp
-          (local.get $1)
-         )
-         (local.set $2
-          (local.get $temp)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
          )
-         (return
-          (local.get $2)
+         (block
+          (local.set $temp
+           (local.get $1)
+          )
+          (local.set $2
+           (local.get $temp)
+          )
+          (return
+           (local.get $2)
+          )
          )
         )
+        (nop)
+        (nop)
        )
-       (nop)
-       (nop)
       )
       (unreachable)
      )
diff --git a/test/passes/asyncify_mod-asyncify-never-unwind.txt b/test/passes/asyncify_mod-asyncify-never-unwind.txt
index eaf2794cf..2177c5220 100644
--- a/test/passes/asyncify_mod-asyncify-never-unwind.txt
+++ b/test/passes/asyncify_mod-asyncify-never-unwind.txt
@@ -164,52 +164,54 @@
        )
       )
       (block
-       (if
-        (if (result i32)
-         (i32.eq
-          (global.get $__asyncify_state)
-          (i32.const 0)
-         )
-         (i32.const 1)
-         (i32.eq
-          (local.get $6)
-          (i32.const 0)
-         )
-        )
-        (block
-         (local.set $7
-          (call $import2)
-         )
-         (if
-          (i32.const 0)
-          (br $__asyncify_unwind
+       (block
+        (if
+         (if (result i32)
+          (i32.eq
+           (global.get $__asyncify_state)
+           (i32.const 0)
+          )
+          (i32.const 1)
+          (i32.eq
+           (local.get $6)
            (i32.const 0)
           )
-          (local.set $1
-           (local.get $7)
+         )
+         (block
+          (local.set $7
+           (call $import2)
+          )
+          (if
+           (i32.const 0)
+           (br $__asyncify_unwind
+            (i32.const 0)
+           )
+           (local.set $1
+            (local.get $7)
+           )
           )
          )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (block
-         (local.set $temp
-          (local.get $1)
-         )
-         (local.set $2
-          (local.get $temp)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
          )
-         (return
-          (local.get $2)
+         (block
+          (local.set $temp
+           (local.get $1)
+          )
+          (local.set $2
+           (local.get $temp)
+          )
+          (return
+           (local.get $2)
+          )
          )
         )
+        (nop)
+        (nop)
        )
-       (nop)
-       (nop)
       )
       (unreachable)
      )
diff --git a/test/passes/asyncify_pass-arg=asyncify-imports@env.import,env.import2.txt b/test/passes/asyncify_pass-arg=asyncify-imports@env.import,env.import2.txt
index defef94ed..2a8c0061a 100644
--- a/test/passes/asyncify_pass-arg=asyncify-imports@env.import,env.import2.txt
+++ b/test/passes/asyncify_pass-arg=asyncify-imports@env.import,env.import2.txt
@@ -488,55 +488,57 @@
        )
       )
       (block
-       (if
-        (if (result i32)
-         (i32.eq
-          (global.get $__asyncify_state)
-          (i32.const 0)
-         )
-         (i32.const 1)
-         (i32.eq
-          (local.get $6)
-          (i32.const 0)
-         )
-        )
-        (block
-         (local.set $7
-          (call $import2)
-         )
-         (if
+       (block
+        (if
+         (if (result i32)
           (i32.eq
            (global.get $__asyncify_state)
-           (i32.const 1)
+           (i32.const 0)
           )
-          (br $__asyncify_unwind
+          (i32.const 1)
+          (i32.eq
+           (local.get $6)
            (i32.const 0)
           )
-          (local.set $1
-           (local.get $7)
+         )
+         (block
+          (local.set $7
+           (call $import2)
+          )
+          (if
+           (i32.eq
+            (global.get $__asyncify_state)
+            (i32.const 1)
+           )
+           (br $__asyncify_unwind
+            (i32.const 0)
+           )
+           (local.set $1
+            (local.get $7)
+           )
           )
          )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (block
-         (local.set $temp
-          (local.get $1)
-         )
-         (local.set $2
-          (local.get $temp)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
          )
-         (return
-          (local.get $2)
+         (block
+          (local.set $temp
+           (local.get $1)
+          )
+          (local.set $2
+           (local.get $temp)
+          )
+          (return
+           (local.get $2)
+          )
          )
         )
+        (nop)
+        (nop)
        )
-       (nop)
-       (nop)
       )
       (unreachable)
      )
@@ -810,84 +812,86 @@
        )
       )
       (block
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (loop $l
-         (local.set $2
-          (local.get $y)
-         )
-         (local.set $3
-          (i32.add
-           (local.get $2)
-           (i32.const 1)
-          )
-         )
-         (local.set $x
-          (local.get $3)
-         )
-         (local.set $4
-          (local.get $x)
-         )
-         (local.set $5
-          (i32.div_s
-           (local.get $4)
-           (i32.const 3)
-          )
-         )
-         (local.set $y
-          (local.get $5)
-         )
-         (local.set $6
-          (local.get $y)
-         )
-         (br_if $l
-          (local.get $6)
-         )
-        )
-       )
-       (if
-        (if (result i32)
+       (block
+        (if
          (i32.eq
           (global.get $__asyncify_state)
           (i32.const 0)
          )
-         (i32.const 1)
-         (i32.eq
-          (local.get $11)
-          (i32.const 0)
+         (loop $l
+          (local.set $2
+           (local.get $y)
+          )
+          (local.set $3
+           (i32.add
+            (local.get $2)
+            (i32.const 1)
+           )
+          )
+          (local.set $x
+           (local.get $3)
+          )
+          (local.set $4
+           (local.get $x)
+          )
+          (local.set $5
+           (i32.div_s
+            (local.get $4)
+            (i32.const 3)
+           )
+          )
+          (local.set $y
+           (local.get $5)
+          )
+          (local.set $6
+           (local.get $y)
+          )
+          (br_if $l
+           (local.get $6)
+          )
          )
         )
-        (block
-         (call $import)
-         (if
+        (if
+         (if (result i32)
           (i32.eq
            (global.get $__asyncify_state)
-           (i32.const 1)
+           (i32.const 0)
           )
-          (br $__asyncify_unwind
+          (i32.const 1)
+          (i32.eq
+           (local.get $11)
            (i32.const 0)
           )
          )
+         (block
+          (call $import)
+          (if
+           (i32.eq
+            (global.get $__asyncify_state)
+            (i32.const 1)
+           )
+           (br $__asyncify_unwind
+            (i32.const 0)
+           )
+          )
+         )
         )
-       )
-       (if
-        (i32.eq
-         (global.get $__asyncify_state)
-         (i32.const 0)
-        )
-        (block
-         (local.set $7
-          (local.get $y)
+        (if
+         (i32.eq
+          (global.get $__asyncify_state)
+          (i32.const 0)
          )
-         (return
-          (local.get $7)
+         (block
+          (local.set $7
+           (local.get $y)
+          )
+          (return
+           (local.get $7)
+          )
          )
         )
+        (nop)
        )
-       (nop)
       )
       (unreachable)
      )
@@ -1062,21 +1066,23 @@
   (local $2 i32)
   (local $3 i32)
   (block
-   (local.set $1
-    (local.get $x)
-   )
-   (if
-    (local.get $1)
-    (return
-     (i32.const 1)
+   (block
+    (local.set $1
+     (local.get $x)
     )
-    (call $import3
-     (i32.const 2)
+    (if
+     (local.get $1)
+     (return
+      (i32.const 1)
+     )
+     (call $import3
+      (i32.const 2)
+     )
     )
    )
-  )
-  (return
-   (i32.const 3)
+   (return
+    (i32.const 3)
+   )
   )
  )
  (func $calls-import2-if-else-oneside2 (param $x i32) (result i32)
@@ -1084,21 +1090,23 @@
   (local $2 i32)
   (local $3 i32)
   (block
-   (local.set $1
-    (local.get $x)
-   )
-   (if
-    (local.get $1)
-    (call $import3
-     (i32.const 1)
+   (block
+    (local.set $1
+     (local.get $x)
     )
-    (return
-     (i32.const 2)
+    (if
+     (local.get $1)
+     (call $import3
+      (i32.const 1)
+     )
+     (return
+      (i32.const 2)
+     )
     )
    )
-  )
-  (return
-   (i32.const 3)
+   (return
+    (i32.const 3)
+   )
   )
  )
  (func $calls-loop (param $x i32)
diff --git a/test/passes/dce_all-features.txt b/test/passes/dce_all-features.txt
index 4b76b2f12..4088d5a34 100644
--- a/test/passes/dce_all-features.txt
+++ b/test/passes/dce_all-features.txt
@@ -24,7 +24,9 @@
   )
   (if
    (i32.const 0)
-   (return)
+   (block $out3
+    (return)
+   )
   )
   (block $out4
    (br_table $out4 $out4 $out4 $out4
@@ -41,10 +43,12 @@
   )
   (if
    (i32.const 0)
-   (if
-    (i32.const 0)
-    (unreachable)
-    (unreachable)
+   (block $block4
+    (if
+     (i32.const 0)
+     (unreachable)
+     (unreachable)
+    )
    )
   )
   (if
@@ -69,13 +73,15 @@
   )
   (if
    (i32.const 0)
-   (block $out18
-    (block $in19
-     (br_if $in19
-      (i32.const 1)
+   (block $block11
+    (block $out18
+     (block $in19
+      (br_if $in19
+       (i32.const 1)
+      )
      )
+     (unreachable)
     )
-    (unreachable)
    )
   )
   (block $out20
@@ -96,13 +102,15 @@
   )
   (if
    (i32.const 0)
-   (block $out25
-    (block $in26
-     (br_table $in26 $in26
-      (i32.const 1)
+   (block $block13
+    (block $out25
+     (block $in26
+      (br_table $in26 $in26
+       (i32.const 1)
+      )
      )
+     (unreachable)
     )
-    (unreachable)
    )
   )
   (if
@@ -122,7 +130,7 @@
    (unreachable)
   )
   (block $out29
-   (block
+   (loop $in30
     (br_if $out29
      (i32.const 1)
     )
@@ -131,11 +139,13 @@
   )
   (if
    (i32.const 0)
-   (loop $in32
-    (br_if $in32
-     (i32.const 1)
+   (block $block20
+    (loop $in32
+     (br_if $in32
+      (i32.const 1)
+     )
+     (unreachable)
     )
-    (unreachable)
    )
   )
   (if
@@ -273,8 +283,12 @@
   )
  )
  (func $typed-block-none-then-unreachable (result i32)
-  (return
-   (i32.const 0)
+  (block $top-typed
+   (block $switch$0
+    (return
+     (i32.const 0)
+    )
+   )
   )
  )
  (func $typed-block-remove-br-changes-type (param $$$0 i32) (result i32)
@@ -317,15 +331,19 @@
   )
  )
  (func $unreachable-block-ends-switch (result i32)
-  (block $label$3
-   (nop)
-   (unreachable)
+  (block $label$0
+   (block $label$3
+    (nop)
+    (unreachable)
+   )
   )
  )
  (func $unreachable-block-ends-br_if (result i32)
-  (block $label$2
-   (nop)
-   (unreachable)
+  (block $label$0
+   (block $label$2
+    (nop)
+    (unreachable)
+   )
   )
  )
  (func $unreachable-brs-3 (result i32)
@@ -339,11 +357,15 @@
   (drop
    (i32.const 1)
   )
-  (block
-   (drop
-    (i32.const 4104)
+  (block $label$0
+   (block $label$1
+    (block
+     (drop
+      (i32.const 4104)
+     )
+     (unreachable)
+    )
    )
-   (unreachable)
   )
  )
  (func $call-unreach (param $var$0 i64) (param $var$1 i64) (result i64)
@@ -355,32 +377,36 @@
    (block $label$0 (result i64)
     (local.get $var$1)
    )
-   (block
-    (drop
-     (i64.sub
-      (local.get $var$0)
-      (i64.const 1)
-     )
-    )
+   (block $label$1
     (block
      (drop
-      (block $block (result i64)
-       (local.set $2
-        (local.get $var$0)
+      (i64.sub
+       (local.get $var$0)
+       (i64.const 1)
+      )
+     )
+     (block
+      (drop
+       (block $block (result i64)
+        (local.set $2
+         (local.get $var$0)
+        )
+        (nop)
+        (local.get $2)
        )
-       (nop)
-       (local.get $2)
       )
+      (unreachable)
      )
-     (unreachable)
     )
    )
   )
  )
  (func $br-gone-means-block-type-changes-then-refinalize-at-end-is-too-late (param $var$0 i32) (result i32)
-  (block $block
-   (nop)
-   (unreachable)
+  (block $label$0
+   (block $block
+    (nop)
+    (unreachable)
+   )
   )
  )
  (func $br-with-unreachable-value-should-not-give-a-block-a-value (param $var$0 i32) (result i32)
@@ -397,25 +423,31 @@
   )
  )
  (func $replace-br-value-of-i32-with-unreachable (result i32)
-  (block $label$1
-   (nop)
-   (unreachable)
+  (block $label$0
+   (block $label$1
+    (nop)
+    (unreachable)
+   )
   )
  )
  (func $shorten-block-requires-sync-refinalize (param $var$0 i32) (param $var$1 i32)
   (unreachable)
  )
  (func $block-with-type-but-is-unreachable (param $var$0 i32) (result i32)
-  (block $block
-   (nop)
-   (unreachable)
+  (block $label$0
+   (block $block
+    (nop)
+    (unreachable)
+   )
   )
  )
  (func $if-with-type-but-is-unreachable (param $var$0 i32) (result i32)
-  (if
-   (local.get $var$0)
-   (unreachable)
-   (unreachable)
+  (block $label$0
+   (if
+    (local.get $var$0)
+    (unreachable)
+    (unreachable)
+   )
   )
  )
  (func $unreachable-loop
@@ -423,8 +455,10 @@
  )
  (func $br-block-from-unary (result i32)
   (block $label$6 (result i32)
-   (br $label$6
-    (i32.const 8)
+   (block $label$7
+    (br $label$6
+     (i32.const 8)
+    )
    )
   )
  )
@@ -444,19 +478,23 @@
   )
  )
  (func $replace-with-unreachable-affects-parent (param $var$0 f32) (param $var$1 i64)
-  (drop
-   (i64.const 0)
-  )
-  (if
-   (block $block (result i32)
-    (call $replace-with-unreachable-affects-parent
-     (f32.const 1)
-     (i64.const -15917430362925035)
+  (block $top
+   (block
+    (drop
+     (i64.const 0)
+    )
+    (if
+     (block $block (result i32)
+      (call $replace-with-unreachable-affects-parent
+       (f32.const 1)
+       (i64.const -15917430362925035)
+      )
+      (i32.const 1)
+     )
+     (unreachable)
+     (unreachable)
     )
-    (i32.const 1)
    )
-   (unreachable)
-   (unreachable)
   )
  )
  (func $replace-block-changes-later-when-if-goes
@@ -503,6 +541,7 @@
 )
 (module
  (type $none_=>_none (func))
+ (type $none_=>_i32 (func (result i32)))
  (event $e (attr 0) (param))
  (func $foo
   (nop)
@@ -542,12 +581,68 @@
   )
  )
  (func $throw
-  (throw $e
+  (block $label$0
+   (block $label$1
+    (throw $e
+    )
+   )
   )
  )
  (func $rethrow
-  (rethrow
-   (ref.null exn)
+  (block $label$0
+   (block $label$1
+    (rethrow
+     (ref.null exn)
+    )
+   )
+  )
+ )
+ (func $unnecessary-concrete-block (result i32)
+  (block $foo
+   (nop)
+   (unreachable)
+  )
+ )
+ (func $necessary-concrete-block (result i32)
+  (block $foo (result i32)
+   (br $foo
+    (i32.const 1)
+   )
+  )
+ )
+ (func $unnecessary-concrete-if (result i32)
+  (if
+   (i32.const 0)
+   (return
+    (i32.const 1)
+   )
+   (unreachable)
+  )
+ )
+ (func $unnecessary-concrete-try (result i32)
+  (try
+   (do
+    (unreachable)
+   )
+   (catch
+    (unreachable)
+   )
+  )
+ )
+ (func $note-loss-of-if-children
+  (block $label$1
+   (block $label$2
+    (nop)
+    (unreachable)
+   )
+  )
+ )
+ (func $note-loss-of-non-control-flow-children
+  (block $out
+   (block $block
+    (nop)
+    (unreachable)
+   )
   )
  )
 )
diff --git a/test/passes/dce_all-features.wast b/test/passes/dce_all-features.wast
index bf0c188d0..9ebcccb60 100644
--- a/test/passes/dce_all-features.wast
+++ b/test/passes/dce_all-features.wast
@@ -810,4 +810,61 @@
       )
     )
   )
+
+  (func $unnecessary-concrete-block (result i32)
+    (block $foo (result i32) ;; unnecessary type
+      (nop)
+      (unreachable)
+    )
+  )
+  (func $necessary-concrete-block (result i32)
+    (block $foo (result i32)
+      (br $foo (i32.const 1))
+      (unreachable)
+    )
+  )
+  (func $unnecessary-concrete-if (result i32)
+    (if (result i32) ;; unnecessary type
+      (i32.const 0)
+      (return (i32.const 1))
+      (unreachable)
+    )
+  )
+  (func $unnecessary-concrete-try (result i32)
+    (try (result i32)
+      (do
+        (unreachable)
+      )
+      (catch
+        (unreachable)
+      )
+    )
+  )
+  (func $note-loss-of-if-children
+    (block $label$1
+     (if ;; begins unreachable - type never changes - but after the condition
+         ;; becomes unreachable, it will lose the children, which means no more
+         ;; br to the outer block, changing that type.
+       (block $label$2 (result i32)
+         (nop)
+         (unreachable)
+       )
+       (unreachable)
+       (br $label$1)
+      )
+    )
+  )
+  (func $note-loss-of-non-control-flow-children
+    (block $out
+      (drop
+       (i32.add
+         (block (result i32)
+            (nop)
+            (unreachable)
+         )
+         (br $out) ;; when this is removed as dead, the block becomes unreachable
+       )
+     )
+    )
+  )
 )
diff --git a/test/passes/dce_vacuum.bin.txt b/test/passes/dce_vacuum.bin.txt
deleted file mode 100644
index cee1143d3..000000000
--- a/test/passes/dce_vacuum.bin.txt
+++ /dev/null
@@ -1,98 +0,0 @@
-(module
- (type $f32_f32_=>_f32 (func (param f32 f32) (result f32)))
- (type $f64_f64_=>_f64 (func (param f64 f64) (result f64)))
- (export "f32.compute_radix" (func $0))
- (export "f64.compute_radix" (func $1))
- (func $0 (param $0 f32) (param $1 f32) (result f32)
-  (block $label$1
-   (loop $label$2
-    (br_if $label$2
-     (f32.eq
-      (f32.add
-       (f32.sub
-        (f32.add
-         (local.tee $0
-          (f32.add
-           (local.get $0)
-           (local.get $0)
-          )
-         )
-         (f32.const 1)
-        )
-        (local.get $0)
-       )
-       (f32.const -1)
-      )
-      (f32.const 0)
-     )
-    )
-   )
-   (block
-    (drop
-     (call $0
-      (f32.add
-       (local.get $0)
-       (local.tee $1
-        (f32.add
-         (local.get $1)
-         (f32.const 1)
-        )
-       )
-      )
-      (local.get $0)
-     )
-    )
-    (unreachable)
-   )
-  )
- )
- (func $1 (param $0 f64) (param $1 f64) (result f64)
-  (block $label$1 (result f64)
-   (loop $label$2
-    (br_if $label$2
-     (f64.eq
-      (f64.add
-       (f64.sub
-        (f64.add
-         (local.tee $0
-          (f64.add
-           (local.get $0)
-           (local.get $0)
-          )
-         )
-         (f64.const 1)
-        )
-        (local.get $0)
-       )
-       (f64.const -1)
-      )
-      (f64.const 0)
-     )
-    )
-   )
-   (loop $label$3
-    (br_if $label$3
-     (f64.ne
-      (f64.sub
-       (f64.sub
-        (f64.add
-         (local.get $0)
-         (local.tee $1
-          (f64.add
-           (local.get $1)
-           (f64.const 1)
-          )
-         )
-        )
-        (local.get $0)
-       )
-       (local.get $1)
-      )
-      (f64.const 0)
-     )
-    )
-   )
-   (local.get $1)
-  )
- )
-)
diff --git a/test/passes/dce_vacuum.txt b/test/passes/dce_vacuum.txt
deleted file mode 100644
index 2c4466058..000000000
--- a/test/passes/dce_vacuum.txt
+++ /dev/null
@@ -1,25 +0,0 @@
-(module
- (type $none_=>_i32 (func (result i32)))
- (type $i64_=>_i64 (func (param i64) (result i64)))
- (type $f32_f32_=>_f32 (func (param f32 f32) (result f32)))
- (func $__Z12serveroptionPc (result i32)
-  (return
-   (i32.const 0)
-  )
- )
- (func $drop-unreachable (param $var$0 f32) (param $var$1 f32) (result f32)
-  (unreachable)
- )
- (func $set-unreachable (param $var$0 i64) (result i64)
-  (local $var$1 i64)
-  (local $var$2 i64)
-  (if
-   (i64.eq
-    (local.get $var$1)
-    (i64.const 0)
-   )
-   (unreachable)
-   (unreachable)
-  )
- )
-)
diff --git a/test/passes/dce_vacuum.wasm b/test/passes/dce_vacuum.wasm
deleted file mode 100644
index 5fa1892bd..000000000
Binary files a/test/passes/dce_vacuum.wasm and /dev/null differ
diff --git a/test/passes/dce_vacuum.wast b/test/passes/dce_vacuum.wast
deleted file mode 100644
index 47f4affbd..000000000
--- a/test/passes/dce_vacuum.wast
+++ /dev/null
@@ -1,51 +0,0 @@
-(module
-  (func $__Z12serveroptionPc (result i32)
-    (block $switch$0
-      (return
-        (i32.const 0)
-      )
-      (br $switch$0)
-    )
-    (return
-      (i32.const 0)
-    )
-  )
-  (func $drop-unreachable (param $var$0 f32) (param $var$1 f32) (result f32)
-   (block $label$0 (result f32)
-    (loop $label$2
-     (drop
-      (unreachable)
-     )
-     (unreachable)
-    )
-    (local.get $var$1)
-   )
-  )
-
- (func $set-unreachable (param $var$0 i64) (result i64)
-  (local $var$1 i64)
-  (local $var$2 i64)
-  (block $label$0 (result i64)
-   (block $label$1
-    (loop $label$2
-     (if
-      (i64.eq
-       (local.get $var$1)
-       (i64.const 0)
-      )
-      (unreachable)
-      (local.set $var$2
-       (i64.mul
-        (unreachable)
-        (local.get $var$2)
-       )
-      )
-     )
-     (br $label$2)
-    )
-   )
-   (local.get $var$2)
-  )
- )
-)
-
diff --git a/test/passes/dce_vacuum_remove-unused-names.bin.txt b/test/passes/dce_vacuum_remove-unused-names.bin.txt
new file mode 100644
index 000000000..26e2c565a
--- /dev/null
+++ b/test/passes/dce_vacuum_remove-unused-names.bin.txt
@@ -0,0 +1,94 @@
+(module
+ (type $f32_f32_=>_f32 (func (param f32 f32) (result f32)))
+ (type $f64_f64_=>_f64 (func (param f64 f64) (result f64)))
+ (export "f32.compute_radix" (func $0))
+ (export "f64.compute_radix" (func $1))
+ (func $0 (param $0 f32) (param $1 f32) (result f32)
+  (loop $label$2
+   (br_if $label$2
+    (f32.eq
+     (f32.add
+      (f32.sub
+       (f32.add
+        (local.tee $0
+         (f32.add
+          (local.get $0)
+          (local.get $0)
+         )
+        )
+        (f32.const 1)
+       )
+       (local.get $0)
+      )
+      (f32.const -1)
+     )
+     (f32.const 0)
+    )
+   )
+  )
+  (block
+   (drop
+    (call $0
+     (f32.add
+      (local.get $0)
+      (local.tee $1
+       (f32.add
+        (local.get $1)
+        (f32.const 1)
+       )
+      )
+     )
+     (local.get $0)
+    )
+   )
+   (unreachable)
+  )
+ )
+ (func $1 (param $0 f64) (param $1 f64) (result f64)
+  (loop $label$2
+   (br_if $label$2
+    (f64.eq
+     (f64.add
+      (f64.sub
+       (f64.add
+        (local.tee $0
+         (f64.add
+          (local.get $0)
+          (local.get $0)
+         )
+        )
+        (f64.const 1)
+       )
+       (local.get $0)
+      )
+      (f64.const -1)
+     )
+     (f64.const 0)
+    )
+   )
+  )
+  (loop $label$3
+   (br_if $label$3
+    (f64.ne
+     (f64.sub
+      (f64.sub
+       (f64.add
+        (local.get $0)
+        (local.tee $1
+         (f64.add
+          (local.get $1)
+          (f64.const 1)
+         )
+        )
+       )
+       (local.get $0)
+      )
+      (local.get $1)
+     )
+     (f64.const 0)
+    )
+   )
+  )
+  (local.get $1)
+ )
+)
diff --git a/test/passes/dce_vacuum_remove-unused-names.txt b/test/passes/dce_vacuum_remove-unused-names.txt
new file mode 100644
index 000000000..2c4466058
--- /dev/null
+++ b/test/passes/dce_vacuum_remove-unused-names.txt
@@ -0,0 +1,25 @@
+(module
+ (type $none_=>_i32 (func (result i32)))
+ (type $i64_=>_i64 (func (param i64) (result i64)))
+ (type $f32_f32_=>_f32 (func (param f32 f32) (result f32)))
+ (func $__Z12serveroptionPc (result i32)
+  (return
+   (i32.const 0)
+  )
+ )
+ (func $drop-unreachable (param $var$0 f32) (param $var$1 f32) (result f32)
+  (unreachable)
+ )
+ (func $set-unreachable (param $var$0 i64) (result i64)
+  (local $var$1 i64)
+  (local $var$2 i64)
+  (if
+   (i64.eq
+    (local.get $var$1)
+    (i64.const 0)
+   )
+   (unreachable)
+   (unreachable)
+  )
+ )
+)
diff --git a/test/passes/dce_vacuum_remove-unused-names.wasm b/test/passes/dce_vacuum_remove-unused-names.wasm
new file mode 100644
index 000000000..5fa1892bd
Binary files /dev/null and b/test/passes/dce_vacuum_remove-unused-names.wasm differ
diff --git a/test/passes/dce_vacuum_remove-unused-names.wast b/test/passes/dce_vacuum_remove-unused-names.wast
new file mode 100644
index 000000000..47f4affbd
--- /dev/null
+++ b/test/passes/dce_vacuum_remove-unused-names.wast
@@ -0,0 +1,51 @@
+(module
+  (func $__Z12serveroptionPc (result i32)
+    (block $switch$0
+      (return
+        (i32.const 0)
+      )
+      (br $switch$0)
+    )
+    (return
+      (i32.const 0)
+    )
+  )
+  (func $drop-unreachable (param $var$0 f32) (param $var$1 f32) (result f32)
+   (block $label$0 (result f32)
+    (loop $label$2
+     (drop
+      (unreachable)
+     )
+     (unreachable)
+    )
+    (local.get $var$1)
+   )
+  )
+
+ (func $set-unreachable (param $var$0 i64) (result i64)
+  (local $var$1 i64)
+  (local $var$2 i64)
+  (block $label$0 (result i64)
+   (block $label$1
+    (loop $label$2
+     (if
+      (i64.eq
+       (local.get $var$1)
+       (i64.const 0)
+      )
+      (unreachable)
+      (local.set $var$2
+       (i64.mul
+        (unreachable)
+        (local.get $var$2)
+       )
+      )
+     )
+     (br $label$2)
+    )
+   )
+   (local.get $var$2)
+  )
+ )
+)
+
diff --git a/test/passes/interesting-pass-mix.txt b/test/passes/interesting-pass-mix.txt
index 0fbbc809c..c37414599 100644
--- a/test/passes/interesting-pass-mix.txt
+++ b/test/passes/interesting-pass-mix.txt
@@ -41,14 +41,16 @@
   )
   (loop $shape$4$continue
    (call $trivial)
-   (br_if $shape$4$continue
+   (if
     (local.get $0)
+    (br $shape$4$continue)
    )
   )
   (loop $shape$6$continue
    (call $trivial)
-   (br_if $shape$6$continue
+   (if
     (local.get $0)
+    (br $shape$6$continue)
    )
   )
  )
@@ -119,8 +121,9 @@
    (call $before-and-after
     (i32.const 9)
    )
-   (br_if $shape$4$continue
+   (if
     (local.get $0)
+    (br $shape$4$continue)
    )
   )
   (call $before-and-after
@@ -187,9 +190,12 @@
   )
   (block $block$7$break
    (block $switch$3$default
-    (br_table $block$7$break $block$7$break $block$7$break $switch$3$default
-     (local.get $0)
+    (block $switch$3$case$7
+     (br_table $switch$3$case$7 $switch$3$case$7 $switch$3$case$7 $switch$3$default
+      (local.get $0)
+     )
     )
+    (br $block$7$break)
    )
    (call $switch
     (i32.const 2)
@@ -212,8 +218,9 @@
     (call $if-br-wat
      (i32.const 1)
     )
-    (br_if $block$2$break
+    (if
      (local.get $0)
+     (br $block$2$break)
     )
    )
    (call $if-br-wat
diff --git a/test/wasm2js/br.2asm.js b/test/wasm2js/br.2asm.js
index 73484e457..c60de9fc2 100644
--- a/test/wasm2js/br.2asm.js
+++ b/test/wasm2js/br.2asm.js
@@ -106,8 +106,10 @@ function asmFunc(global, env) {
  function $13() {
   var $0 = 0, $1_1 = 0, $3_1 = 0;
   block : {
-   $0 = 3;
-   break block;
+   loop_in : while (1) {
+    $0 = 3;
+    break block;
+   };
   }
   return $0 | 0;
  }
@@ -115,9 +117,11 @@ function asmFunc(global, env) {
  function $14() {
   var $0 = 0, $1_1 = 0, $3_1 = 0;
   block : {
-   dummy();
-   $0 = 4;
-   break block;
+   loop_in : while (1) {
+    dummy();
+    $0 = 4;
+    break block;
+   };
   }
   return $0 | 0;
  }
@@ -125,9 +129,11 @@ function asmFunc(global, env) {
  function $15() {
   var $0 = 0;
   block : {
-   dummy();
-   $0 = 5;
-   break block;
+   loop_in : while (1) {
+    dummy();
+    $0 = 5;
+    break block;
+   };
   }
   return $0 | 0;
  }
diff --git a/test/wasm2js/br_table.2asm.js b/test/wasm2js/br_table.2asm.js
index 4171374b9..5e1c2c05c 100644
--- a/test/wasm2js/br_table.2asm.js
+++ b/test/wasm2js/br_table.2asm.js
@@ -12560,10 +12560,12 @@ function asmFunc(global, env) {
  function $20() {
   var $1_1 = 0, $2_1 = 0, $4_1 = 0;
   fake_return_waka123 : {
-   $1_1 = 3;
-   switch (0 | 0) {
-   default:
-    break fake_return_waka123;
+   loop_in : while (1) {
+    $1_1 = 3;
+    switch (0 | 0) {
+    default:
+     break fake_return_waka123;
+    };
    };
   }
   return $1_1 | 0;
@@ -12572,11 +12574,13 @@ function asmFunc(global, env) {
  function $21() {
   var $1_1 = 0, $2_1 = 0, $4_1 = 0;
   fake_return_waka123 : {
-   dummy();
-   $1_1 = 4;
-   switch (-1 | 0) {
-   default:
-    break fake_return_waka123;
+   loop_in : while (1) {
+    dummy();
+    $1_1 = 4;
+    switch (-1 | 0) {
+    default:
+     break fake_return_waka123;
+    };
    };
   }
   return $1_1 | 0;
@@ -12585,11 +12589,13 @@ function asmFunc(global, env) {
  function $22() {
   var $1_1 = 0;
   fake_return_waka123 : {
-   dummy();
-   $1_1 = 5;
-   switch (1 | 0) {
-   default:
-    break fake_return_waka123;
+   loop_in : while (1) {
+    dummy();
+    $1_1 = 5;
+    switch (1 | 0) {
+    default:
+     break fake_return_waka123;
+    };
    };
   }
   return $1_1 | 0;
diff --git a/test/wasm2js/br_table_temp.2asm.js b/test/wasm2js/br_table_temp.2asm.js
index 3a56dda00..99d7ceeef 100644
--- a/test/wasm2js/br_table_temp.2asm.js
+++ b/test/wasm2js/br_table_temp.2asm.js
@@ -12556,10 +12556,12 @@ function asmFunc(global, env) {
  function $20() {
   var $1_1 = 0, $2_1 = 0, $4_1 = 0;
   fake_return_waka123 : {
-   $1_1 = 3;
-   switch (0 | 0) {
-   default:
-    break fake_return_waka123;
+   loop_in : while (1) {
+    $1_1 = 3;
+    switch (0 | 0) {
+    default:
+     break fake_return_waka123;
+    };
    };
   }
   return $1_1 | 0;
@@ -12568,11 +12570,13 @@ function asmFunc(global, env) {
  function $21() {
   var $1_1 = 0, $2_1 = 0, $4_1 = 0;
   fake_return_waka123 : {
-   dummy();
-   $1_1 = 4;
-   switch (-1 | 0) {
-   default:
-    break fake_return_waka123;
+   loop_in : while (1) {
+    dummy();
+    $1_1 = 4;
+    switch (-1 | 0) {
+    default:
+     break fake_return_waka123;
+    };
    };
   }
   return $1_1 | 0;
@@ -12581,11 +12585,13 @@ function asmFunc(global, env) {
  function $22() {
   var $1_1 = 0;
   fake_return_waka123 : {
-   dummy();
-   $1_1 = 5;
-   switch (1 | 0) {
-   default:
-    break fake_return_waka123;
+   loop_in : while (1) {
+    dummy();
+    $1_1 = 5;
+    switch (1 | 0) {
+    default:
+     break fake_return_waka123;
+    };
    };
   }
   return $1_1 | 0;
diff --git a/test/wasm2js/excess_fallthrough.2asm.js b/test/wasm2js/excess_fallthrough.2asm.js
index d1290aa50..3c8d09bf4 100644
--- a/test/wasm2js/excess_fallthrough.2asm.js
+++ b/test/wasm2js/excess_fallthrough.2asm.js
@@ -18,20 +18,22 @@ function asmFunc(global, env) {
  
  function foo($0) {
   $0 = $0 | 0;
-  label$5 : {
-   bar();
-   block : {
-    switch (123 | 0) {
-    case 0:
-     bar();
-     break;
-    default:
-     break label$5;
-    };
+  label$4 : while (1) {
+   label$5 : {
+    bar();
+    block : {
+     switch (123 | 0) {
+     case 0:
+      bar();
+      break;
+     default:
+      break label$5;
+     };
+    }
+    return;
    }
-   return;
-  }
-  abort();
+   abort();
+  };
  }
  
  return {
-- 
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