[Wasm GC] Fix RemoveUnusedModuleEffects struct field reads with call.without.effects (#5477)

If we see

(struct.new $A
  (call $call.without.effects ;; intrinsic
    (ref.func $getter)
  )
)

then we can ignore side effects in that call, as the intrinsic tells us to. However,
that function is still called (it will be called normally, after intrinsics are lowered
away), and we should not remove it.

That is, such an intrinsic call can be removed, but it cannot be left as it is
and also ignored as if it does not exist.

1 files changed, 73 insertions, 0 deletions

diff --git a/test/lit/passes/remove-unused-module-elements-refs.wast b/test/lit/passes/remove-unused-module-elements-refs.wast
index 2bbba0cad..61ccb4daf 100644
--- a/test/lit/passes/remove-unused-module-elements-refs.wast
+++ b/test/lit/passes/remove-unused-module-elements-refs.wast
@@ -1841,3 +1841,76 @@
   (func $f (type $void)
   )
 )
+
+;; The call.without.effects intrinsic reports itself as having no side effects.
+;; We do still need to consider the target as being called, however, even if it
+;; is in a struct field.
+(module
+  ;; CHECK:      (type $funcref_=>_i32 (func (param funcref) (result i32)))
+
+  ;; CHECK:      (type $none_=>_none (func))
+
+  ;; CHECK:      (type $A (struct (field i32)))
+  ;; OPEN_WORLD:      (type $funcref_=>_i32 (func (param funcref) (result i32)))
+
+  ;; OPEN_WORLD:      (type $none_=>_none (func))
+
+  ;; OPEN_WORLD:      (type $A (struct (field i32)))
+  (type $A (struct (field i32)))
+
+  ;; CHECK:      (type $none_=>_i32 (func (result i32)))
+
+  ;; CHECK:      (import "binaryen-intrinsics" "call.without.effects" (func $call.without.effects (param funcref) (result i32)))
+  ;; OPEN_WORLD:      (type $none_=>_i32 (func (result i32)))
+
+  ;; OPEN_WORLD:      (import "binaryen-intrinsics" "call.without.effects" (func $call.without.effects (param funcref) (result i32)))
+  (import "binaryen-intrinsics" "call.without.effects" (func $call.without.effects (param funcref) (result i32)))
+
+  ;; CHECK:      (elem declare func $getter)
+
+  ;; CHECK:      (export "main" (func $main))
+
+  ;; CHECK:      (func $main (type $none_=>_none)
+  ;; CHECK-NEXT:  (drop
+  ;; CHECK-NEXT:   (struct.new $A
+  ;; CHECK-NEXT:    (call $call.without.effects
+  ;; CHECK-NEXT:     (ref.func $getter)
+  ;; CHECK-NEXT:    )
+  ;; CHECK-NEXT:   )
+  ;; CHECK-NEXT:  )
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (elem declare func $getter)
+
+  ;; OPEN_WORLD:      (export "main" (func $main))
+
+  ;; OPEN_WORLD:      (func $main (type $none_=>_none)
+  ;; OPEN_WORLD-NEXT:  (drop
+  ;; OPEN_WORLD-NEXT:   (struct.new $A
+  ;; OPEN_WORLD-NEXT:    (call $call.without.effects
+  ;; OPEN_WORLD-NEXT:     (ref.func $getter)
+  ;; OPEN_WORLD-NEXT:    )
+  ;; OPEN_WORLD-NEXT:   )
+  ;; OPEN_WORLD-NEXT:  )
+  ;; OPEN_WORLD-NEXT: )
+  (func $main (export "main")
+    (drop
+      (struct.new $A
+        (call $call.without.effects
+          (ref.func $getter)
+        )
+      )
+    )
+  )
+
+  ;; CHECK:      (func $getter (type $none_=>_i32) (result i32)
+  ;; CHECK-NEXT:  (i32.const 42)
+  ;; CHECK-NEXT: )
+  ;; OPEN_WORLD:      (func $getter (type $none_=>_i32) (result i32)
+  ;; OPEN_WORLD-NEXT:  (i32.const 42)
+  ;; OPEN_WORLD-NEXT: )
+  (func $getter (result i32)
+    ;; This function body should not be turned into an unreachable. It is
+    ;; reached from $main, even though the call is marked as not having effects.
+    (i32.const 42)
+  )
+)