[Wasm GC] Optimize br_on_* (#3719)

The type may prove the value is not null, and may also show it to be
of the type we are casting to. In that case, we can simplify things.

2 files changed, 129 insertions, 1 deletions

diff --git a/test/passes/remove-unused-brs_all-features.txt b/test/passes/remove-unused-brs_all-features.txt
index f8308c65f..0c830cbc0 100644
--- a/test/passes/remove-unused-brs_all-features.txt
+++ b/test/passes/remove-unused-brs_all-features.txt
@@ -2,11 +2,13 @@
  (type $struct (struct (field (ref null $vector))))
  (type $vector (array (mut i32)))
  (type $i32_=>_none (func (param i32)))
+ (type $ref|func|_=>_none (func (param (ref func))))
  (type $none_=>_i32 (func (result i32)))
  (type $none_=>_f64 (func (result f64)))
  (type $i32_=>_funcref (func (param i32) (result funcref)))
  (type $none_=>_ref?|$struct| (func (result (ref null $struct))))
- (elem declare func $i32_=>_none $none_=>_i32)
+ (import "out" "log" (func $log (param i32)))
+ (elem declare func $br_on-to-br $i32_=>_none $none_=>_i32)
  (func $foo (result (ref null $struct))
   (if (result (ref null $struct))
    (i32.const 1)
@@ -50,4 +52,75 @@
    (local.get $x)
   )
  )
+ (func $br_on-to-br (param $func (ref func))
+  (call $log
+   (i32.const 0)
+  )
+  (block $null
+   (drop
+    (ref.func $br_on-to-br)
+   )
+   (call $log
+    (i32.const 1)
+   )
+  )
+  (call $log
+   (i32.const 2)
+  )
+  (drop
+   (block $func (result funcref)
+    (drop
+     (br $func
+      (ref.func $br_on-to-br)
+     )
+    )
+    (call $log
+     (i32.const 3)
+    )
+    (ref.func $br_on-to-br)
+   )
+  )
+  (call $log
+   (i32.const 4)
+  )
+  (drop
+   (block $data (result dataref)
+    (drop
+     (br $data
+      (array.new_default_with_rtt $vector
+       (i32.const 1)
+       (rtt.canon $vector)
+      )
+     )
+    )
+    (call $log
+     (i32.const 5)
+    )
+    (array.new_default_with_rtt $vector
+     (i32.const 2)
+     (rtt.canon $vector)
+    )
+   )
+  )
+  (call $log
+   (i32.const 6)
+  )
+  (drop
+   (block $i31 (result i31ref)
+    (drop
+     (br $i31
+      (i31.new
+       (i32.const 42)
+      )
+     )
+    )
+    (call $log
+     (i32.const 7)
+    )
+    (i31.new
+     (i32.const 1337)
+    )
+   )
+  )
+ )
 )
diff --git a/test/passes/remove-unused-brs_all-features.wast b/test/passes/remove-unused-brs_all-features.wast
index 1da00291d..4f66f2fdd 100644
--- a/test/passes/remove-unused-brs_all-features.wast
+++ b/test/passes/remove-unused-brs_all-features.wast
@@ -1,6 +1,7 @@
 (module
  (type $vector (array (mut i32)))
  (type $struct (struct (field (ref null $vector))))
+ (import "out" "log" (func $log (param i32)))
  (func $foo (result (ref null $struct))
   (if (result (ref null $struct))
    (i32.const 1)
@@ -53,4 +54,58 @@
    (ref.func $i32_=>_none)
   )
  )
+
+ (func $br_on-to-br (param $func (ref func))
+  (call $log (i32.const 0))
+  (block $null
+   ;; a non-null reference is not null, and the br is never taken
+   (drop
+    (br_on_null $null (ref.func $br_on-to-br))
+   )
+   (call $log (i32.const 1))
+  )
+  (call $log (i32.const 2))
+  (drop
+   (block $func (result funcref)
+    ;; a non-null function reference means we always take the br
+    (drop
+     (br_on_func $func (ref.func $br_on-to-br))
+    )
+    (call $log (i32.const 3))
+    (ref.func $br_on-to-br)
+   )
+  )
+  (call $log (i32.const 4))
+  (drop
+   (block $data (result dataref)
+    ;; a non-null data reference means we always take the br
+    (drop
+     (br_on_data $data
+      (array.new_default_with_rtt $vector
+       (i32.const 1)
+       (rtt.canon $vector)
+      )
+     )
+    )
+    (call $log (i32.const 5))
+    (array.new_default_with_rtt $vector
+     (i32.const 2)
+     (rtt.canon $vector)
+    )
+   )
+  )
+  (call $log (i32.const 6))
+  (drop
+   (block $i31 (result i31ref)
+    ;; a non-null i31 reference means we always take the br
+    (drop
+     (br_on_i31 $i31
+      (i31.new (i32.const 42))
+     )
+    )
+    (call $log (i32.const 7))
+    (i31.new (i32.const 1337))
+   )
+  )
+ )
 )