remove-unused-brs: do not flow a value through a block if the block does not actually flow a value. fixes #1833 (#1835)

2 files changed, 63 insertions, 8 deletions

diff --git a/test/passes/remove-unused-brs.txt b/test/passes/remove-unused-brs.txt
index 48cfad529..889e358c7 100644
--- a/test/passes/remove-unused-brs.txt
+++ b/test/passes/remove-unused-brs.txt
@@ -2212,21 +2212,20 @@
  (func $refinalize-need-br-value (; 101 ;) (type $2) (result i32)
   (loop $label$3 (result i32)
    (block $label$6 (result i32)
-    (block $label$10 (result i32)
+    (block $label$10
      (unreachable)
-     (block $label$503 (result i32)
+     (block $label$503
       (br_if $label$3
        (block $label$530 (result i32)
-        (block
-         (unreachable)
-         (drop
-          (i32.const 0)
-         )
+        (br_if $label$503
+         (i32.const 0)
         )
         (i32.const 0)
        )
       )
-      (i32.const 127)
+      (return
+       (i32.const 127)
+      )
      )
     )
    )
@@ -2404,4 +2403,32 @@
    (i32.const 1)
   )
  )
+ (func $do-not-flow-values-through-unreachable-code (; 113 ;) (type $2) (result i32)
+  (block $block
+   (unreachable)
+   (if
+    (i32.const 0)
+    (block $A
+     (return
+      (i32.const 0)
+     )
+    )
+    (nop)
+   )
+  )
+ )
+ (func $do-not-flow-values-through-unreachable-code-b (; 114 ;) (type $2) (result i32)
+  (loop $loop-in
+   (unreachable)
+   (if
+    (i32.const 0)
+    (block $A
+     (return
+      (i32.const 0)
+     )
+    )
+    (nop)
+   )
+  )
+ )
 )
diff --git a/test/passes/remove-unused-brs.wast b/test/passes/remove-unused-brs.wast
index 9d53f4fda..71f39e331 100644
--- a/test/passes/remove-unused-brs.wast
+++ b/test/passes/remove-unused-brs.wast
@@ -2011,5 +2011,33 @@
       )
     )
   )
+  (func $do-not-flow-values-through-unreachable-code (result i32)
+   (block
+    (unreachable)
+    (block $A
+     (if
+      (i32.const 0)
+      (return
+       (i32.const 0) ;; seems to flow out, but we are in unreachable code, and do not actually reach anywhere
+      )
+      (br $A) ;; can be a nop
+     )
+    )
+   )
+  )
+  (func $do-not-flow-values-through-unreachable-code-b (result i32)
+   (loop
+    (unreachable)
+    (block $A
+     (if
+      (i32.const 0)
+      (return
+       (i32.const 0)
+      )
+      (br $A)
+     )
+    )
+   )
+  )
 )