Consolidate br_on* operations (#5399)

The `br_on{_non}_{data,i31,func}` operations are deprecated and directly
representable in terms of the new `br_on_cast` and `br_on_cast_fail`
instructions, so remove their dedicated IR opcodes in favor of representing them
as casts. `br_on_null` and `br_on_non_null` cannot be consolidated the same way
because their behavior is not directly representable in terms of `br_on_cast`
and `br_on_cast_fail`; when the cast to null bottom type succeeds, the null
check instructions implicitly drop the null value whereas the cast instructions
would propagate it.

Add special logic to the binary writer and printer to continue emitting the
deprecated instructions for now. This will allow us to update the test suite in
a separate future PR with no additional functional changes.

Some tests are updated because the validator no longer allows passing non-func
data to `br_on_func`. Doing so has not made sense since we separated the three
reference type hierarchies.

8 files changed, 16 insertions, 230 deletions

diff --git a/test/heap-types.wast b/test/heap-types.wast
index 9366dca01..f75622142 100644
--- a/test/heap-types.wast
+++ b/test/heap-types.wast
@@ -203,14 +203,6 @@
       )
     )
     (drop
-      (block $func (result funcref)
-        (local.set $y
-          (br_on_func $func (local.get $x))
-        )
-        (ref.null func)
-      )
-    )
-    (drop
       (block $i31 (result (ref null i31))
         (local.set $y
           (br_on_i31 $i31 (local.get $x))
@@ -225,14 +217,6 @@
       )
     )
     (drop
-      (block $non-func (result anyref)
-        (local.set $temp-func
-          (br_on_non_func $non-func (local.get $x))
-        )
-        (ref.null any)
-      )
-    )
-    (drop
       (block $non-i31 (result anyref)
         (local.set $temp-i31
           (br_on_non_i31 $non-i31 (local.get $x))
diff --git a/test/heap-types.wast.from-wast b/test/heap-types.wast.from-wast
index 9f1a28d13..9eafd633b 100644
--- a/test/heap-types.wast.from-wast
+++ b/test/heap-types.wast.from-wast
@@ -230,16 +230,6 @@
    )
   )
   (drop
-   (block $func (result funcref)
-    (local.set $y
-     (br_on_func $func
-      (local.get $x)
-     )
-    )
-    (ref.null nofunc)
-   )
-  )
-  (drop
    (block $i31 (result i31ref)
     (local.set $y
      (br_on_i31 $i31
@@ -258,16 +248,6 @@
    )
   )
   (drop
-   (block $non-func (result anyref)
-    (local.set $temp-func
-     (br_on_non_func $non-func
-      (local.get $x)
-     )
-    )
-    (ref.null none)
-   )
-  )
-  (drop
    (block $non-i31 (result anyref)
     (local.set $temp-i31
      (br_on_non_i31 $non-i31
diff --git a/test/heap-types.wast.fromBinary b/test/heap-types.wast.fromBinary
index b217ebc2e..04e9bbe05 100644
--- a/test/heap-types.wast.fromBinary
+++ b/test/heap-types.wast.fromBinary
@@ -228,19 +228,9 @@
    )
   )
   (drop
-   (block $label$2 (result funcref)
+   (block $label$2 (result i31ref)
     (local.set $y
-     (br_on_func $label$2
-      (local.get $x)
-     )
-    )
-    (ref.null nofunc)
-   )
-  )
-  (drop
-   (block $label$3 (result i31ref)
-    (local.set $y
-     (br_on_i31 $label$3
+     (br_on_i31 $label$2
       (local.get $x)
      )
     )
@@ -248,27 +238,17 @@
    )
   )
   (drop
-   (block $label$4 (result (ref any))
-    (br_on_non_null $label$4
+   (block $label$3 (result (ref any))
+    (br_on_non_null $label$3
      (local.get $x)
     )
     (unreachable)
    )
   )
   (drop
-   (block $label$5 (result anyref)
-    (local.set $temp-func
-     (br_on_non_func $label$5
-      (local.get $x)
-     )
-    )
-    (ref.null none)
-   )
-  )
-  (drop
-   (block $label$6 (result anyref)
+   (block $label$4 (result anyref)
     (local.set $temp-i31
-     (br_on_non_i31 $label$6
+     (br_on_non_i31 $label$4
       (local.get $x)
      )
     )
diff --git a/test/heap-types.wast.fromBinary.noDebugInfo b/test/heap-types.wast.fromBinary.noDebugInfo
index 89f0c676e..472c3288f 100644
--- a/test/heap-types.wast.fromBinary.noDebugInfo
+++ b/test/heap-types.wast.fromBinary.noDebugInfo
@@ -228,19 +228,9 @@
    )
   )
   (drop
-   (block $label$2 (result funcref)
+   (block $label$2 (result i31ref)
     (local.set $1
-     (br_on_func $label$2
-      (local.get $0)
-     )
-    )
-    (ref.null nofunc)
-   )
-  )
-  (drop
-   (block $label$3 (result i31ref)
-    (local.set $1
-     (br_on_i31 $label$3
+     (br_on_i31 $label$2
       (local.get $0)
      )
     )
@@ -248,27 +238,17 @@
    )
   )
   (drop
-   (block $label$4 (result (ref any))
-    (br_on_non_null $label$4
+   (block $label$3 (result (ref any))
+    (br_on_non_null $label$3
      (local.get $0)
     )
     (unreachable)
    )
   )
   (drop
-   (block $label$5 (result anyref)
-    (local.set $3
-     (br_on_non_func $label$5
-      (local.get $0)
-     )
-    )
-    (ref.null none)
-   )
-  )
-  (drop
-   (block $label$6 (result anyref)
+   (block $label$4 (result anyref)
     (local.set $4
-     (br_on_non_i31 $label$6
+     (br_on_non_i31 $label$4
       (local.get $0)
      )
     )
diff --git a/test/lit/cast-to-basic.wast b/test/lit/cast-to-basic.wast
index 1aa329bf5..239fd820c 100644
--- a/test/lit/cast-to-basic.wast
+++ b/test/lit/cast-to-basic.wast
@@ -35,7 +35,7 @@
   ;; CHECK-NEXT:  (drop
   ;; CHECK-NEXT:   (block $label$1 (result dataref)
   ;; CHECK-NEXT:    (drop
-  ;; CHECK-NEXT:     (br_on_cast $label$1 data
+  ;; CHECK-NEXT:     (br_on_data $label$1
   ;; CHECK-NEXT:      (ref.null none)
   ;; CHECK-NEXT:     )
   ;; CHECK-NEXT:    )
diff --git a/test/lit/passes/gufa-refs.wast b/test/lit/passes/gufa-refs.wast
index 9f45ab62a..f1ea265d7 100644
--- a/test/lit/passes/gufa-refs.wast
+++ b/test/lit/passes/gufa-refs.wast
@@ -14,8 +14,6 @@
 
   ;; CHECK:      (type $none_=>_ref|any| (func (result (ref any))))
 
-  ;; CHECK:      (type $none_=>_funcref (func (result funcref)))
-
   ;; CHECK:      (import "a" "b" (func $import (result i32)))
   (import "a" "b" (func $import (result i32)))
 
@@ -58,7 +56,7 @@
         (nop)
         (ref.as_func
           (ref.as_non_null
-            (ref.null any)
+            (ref.null func)
           )
         )
       )
@@ -360,50 +358,6 @@
       (local.get $z)
     )
   )
-
-  ;; CHECK:      (func $nondeterminism (type $none_=>_funcref) (result funcref)
-  ;; CHECK-NEXT:  (block $label$1 (result funcref)
-  ;; CHECK-NEXT:   (drop
-  ;; CHECK-NEXT:    (br_on_func $label$1
-  ;; CHECK-NEXT:     (i31.new
-  ;; CHECK-NEXT:      (i32.const 1337)
-  ;; CHECK-NEXT:     )
-  ;; CHECK-NEXT:    )
-  ;; CHECK-NEXT:   )
-  ;; CHECK-NEXT:   (ref.null nofunc)
-  ;; CHECK-NEXT:  )
-  ;; CHECK-NEXT: )
-  (func $nondeterminism (result funcref)
-    ;; This block is sent an i31 and a null. The null is compatible with the
-    ;; type and the i31 is not. The order in which we process this matters:
-    ;;
-    ;;  * If the i31 arrives first, we'll filter it out as incompatible with the
-    ;;    type of the block. Then the null arrives and the final result is that
-    ;;    null, which we can then optimize the block to return.
-    ;;  * Or, if the null arrives first, then when the i31 arrives the
-    ;;    combination of nullfunc + i31 is Many (since the types are
-    ;;    incompatible). We then filter that to the block's type, ending up with
-    ;;    a cone of funcref. We cannot optimize in that case, unlike before.
-    ;;
-    ;; Ideally we'd optimize here, but atm we do not since the order in
-    ;; practice is a less ideal one. At minimum we should be deterministic in
-    ;; how we handle this, which this test enforces at least.
-    ;;
-    ;; TODO: Find a way to actually optimize such cases, perhaps by filtering
-    ;;       when sending as well and not just when receiving (the br_on_func
-    ;;       here should not send anything, as what it sends should be first
-    ;;       intersected with funcref).
-    (block $label$1 (result funcref)
-      (drop
-        (br_on_func $label$1
-          (i31.new
-            (i32.const 1337)
-          )
-        )
-      )
-      (ref.null nofunc)
-    )
-  )
 )
 
 (module
diff --git a/test/passes/remove-unused-brs_all-features.txt b/test/passes/remove-unused-brs_all-features.txt
index d833e469e..253092e1c 100644
--- a/test/passes/remove-unused-brs_all-features.txt
+++ b/test/passes/remove-unused-brs_all-features.txt
@@ -7,9 +7,8 @@
  (type $none_=>_f64 (func (result f64)))
  (type $none_=>_i32 (func (result i32)))
  (type $i32_=>_funcref (func (param i32) (result funcref)))
- (type $none_=>_none (func))
  (import "out" "log" (func $log (param i32)))
- (elem declare func $br_on-to-br $br_on-to-flow $i32_=>_none $none_=>_i32)
+ (elem declare func $br_on-to-br $i32_=>_none $none_=>_i32)
  (func $foo (type $none_=>_ref?|$struct|) (result (ref null $struct))
   (if (result (ref null $struct))
    (i32.const 1)
@@ -114,44 +113,4 @@
    )
   )
  )
- (func $br_on-to-flow (type $none_=>_none)
-  (drop
-   (block $func (result nullfuncref)
-    (drop
-     (array.new_default $vector
-      (i32.const 2)
-     )
-    )
-    (ref.null nofunc)
-   )
-  )
-  (drop
-   (block $funcb (result nullfuncref)
-    (drop
-     (i31.new
-      (i32.const 1337)
-     )
-    )
-    (ref.null nofunc)
-   )
-  )
-  (drop
-   (block $i31 (result nullref)
-    (drop
-     (array.new_default $vector
-      (i32.const 2)
-     )
-    )
-    (ref.null none)
-   )
-  )
-  (drop
-   (block $i31b (result nullref)
-    (drop
-     (ref.func $br_on-to-flow)
-    )
-    (ref.null none)
-   )
-  )
- )
 )
diff --git a/test/passes/remove-unused-brs_all-features.wast b/test/passes/remove-unused-brs_all-features.wast
index 356616b7b..5960e1029 100644
--- a/test/passes/remove-unused-brs_all-features.wast
+++ b/test/passes/remove-unused-brs_all-features.wast
@@ -96,55 +96,4 @@
    )
   )
  )
-
- ;; a br_on of the obviously incorrect kind can just flow out the value as the
- ;; break is never taken
- (func $br_on-to-flow
-  ;; brs to func
-  (drop
-   (block $func (result (ref null func))
-    (drop
-     (br_on_func $func
-      (array.new_default $vector
-       (i32.const 2)
-      )
-     )
-    )
-    (ref.null func)
-   )
-  )
-  (drop
-   (block $funcb (result (ref null func))
-    (drop
-     (br_on_func $funcb
-      (i31.new (i32.const 1337))
-     )
-    )
-    (ref.null func)
-   )
-  )
-  ;; brs to i31
-  (drop
-   (block $i31 (result (ref null i31))
-    (drop
-     (br_on_i31 $i31
-      (array.new_default $vector
-       (i32.const 2)
-      )
-     )
-    )
-    (ref.null i31)
-   )
-  )
-  (drop
-   (block $i31b (result (ref null i31))
-    (drop
-     (br_on_i31 $i31b
-      (ref.func $br_on-to-flow)
-     )
-    )
-    (ref.null i31)
-   )
-  )
- )
-)
+)
\ No newline at end of file