Fix a fuzz issue with #6984 (#6988)

When I refactored the optimizeDroppedBlock logic in #6982, I didn't move the
unreachability check with that code, which was wrong. When that function
was called from another place in #6984, the fuzzer found an issue.

Diff without whitespace is smaller. This reverts almost all the test updates
from #6984 - those changes were on blocks with unreachable children.
The change was safe on them, but in general removing a block value in the
presence of unreachable code is tricky, so it's best to avoid it.

The testcase is a little bizarre, but it's the one the fuzzer found and I can't
find a way to generate a better one (other than to reduce it, which I did).

3 files changed, 70 insertions, 33 deletions

diff --git a/test/passes/Oz_fuzz-exec_all-features.txt b/test/passes/Oz_fuzz-exec_all-features.txt
index d1a80c318..b69b9728c 100644
--- a/test/passes/Oz_fuzz-exec_all-features.txt
+++ b/test/passes/Oz_fuzz-exec_all-features.txt
@@ -183,10 +183,14 @@
   (nop)
  )
  (func $br-on_non_null-2 (type $void_func)
-  (call $log
-   (i32.const 1)
+  (drop
+   (block
+    (call $log
+     (i32.const 1)
+    )
+    (unreachable)
+   )
   )
-  (unreachable)
  )
  (func $cast-on-func (type $void_func)
   (call $log
diff --git a/test/passes/merge-blocks.txt b/test/passes/merge-blocks.txt
index 96e621704..86d97af4b 100644
--- a/test/passes/merge-blocks.txt
+++ b/test/passes/merge-blocks.txt
@@ -10,12 +10,11 @@
   )
  )
  (func $drop-block-br
-  (block $x
-   (drop
-    (i32.const 1)
-   )
-   (br $x)
-   (drop
+  (drop
+   (block $x (result i32)
+    (br $x
+     (i32.const 1)
+    )
     (i32.const 0)
    )
   )
@@ -78,9 +77,15 @@
   )
  )
  (func $drop-block-squared-iloop
-  (block $label$0
-   (loop $label$2
-    (br $label$2)
+  (drop
+   (block $label$0 (result i32)
+    (drop
+     (block $label$1
+      (loop $label$2
+       (br $label$2)
+      )
+     )
+    )
    )
   )
  )
@@ -104,7 +109,11 @@
  (func $loop-block-drop-block-return
   (loop $label$4
    (block $label$5
-    (return)
+    (drop
+     (block $label$6 (result i32)
+      (return)
+     )
+    )
    )
   )
  )
diff --git a/test/passes/remove-unused-names_merge-blocks_all-features.txt b/test/passes/remove-unused-names_merge-blocks_all-features.txt
index 17ba2bd4d..c1c803af5 100644
--- a/test/passes/remove-unused-names_merge-blocks_all-features.txt
+++ b/test/passes/remove-unused-names_merge-blocks_all-features.txt
@@ -286,11 +286,15 @@
    (i32.const 30)
   )
   (drop
-   (i32.const 10)
-  )
-  (i32.add
-   (unreachable)
-   (i32.const 20)
+   (block
+    (drop
+     (i32.const 10)
+    )
+    (i32.add
+     (unreachable)
+     (i32.const 20)
+    )
+   )
   )
   (drop
    (i32.const 20)
@@ -818,13 +822,17 @@
  )
  (func $drop-unreachable (type $2) (result i32)
   (local $0 i32)
-  (unreachable)
+  (drop
+   (block (result i32)
+    (unreachable)
+   )
+  )
   (unreachable)
  )
  (func $concrete_finale_in_unreachable (type $5) (result f64)
-  (block
-   (unreachable)
-   (drop
+  (drop
+   (block (result f64)
+    (unreachable)
     (f64.const 6.322092475576799e-96)
    )
   )
@@ -832,16 +840,22 @@
  )
  (func $dont-move-unreachable (type $3)
   (loop $label$0
-   (br $label$0)
    (drop
-    (i32.const 1)
+    (block (result i32)
+     (br $label$0)
+     (i32.const 1)
+    )
    )
   )
  )
  (func $dont-move-unreachable-last (type $3)
   (loop $label$0
-   (call $dont-move-unreachable-last)
-   (br $label$0)
+   (drop
+    (block (result i32)
+     (call $dont-move-unreachable-last)
+     (br $label$0)
+    )
+   )
   )
  )
  (func $move-around-unreachable-in-middle (type $3)
@@ -862,10 +876,16 @@
  )
  (func $drop-unreachable-block-with-concrete-final (type $3)
   (drop
-   (return)
-  )
-  (drop
-   (i32.const -452)
+   (block (result i32)
+    (drop
+     (block
+      (drop
+       (return)
+      )
+     )
+    )
+    (i32.const -452)
+   )
   )
  )
  (func $merging-with-unreachable-in-middle (type $2) (result i32)
@@ -881,9 +901,13 @@
  )
  (func $remove-br-after-unreachable (type $3)
   (block $label$9
-   (block
-    (return)
-    (br $label$9)
+   (drop
+    (block
+     (block
+      (return)
+      (br $label$9)
+     )
+    )
    )
   )
  )