From 05004fa127defbceebb2f5cbd7a9f370fd3186f1 Mon Sep 17 00:00:00 2001
From: dcode <dcode@dcode.io>
Date: Fri, 20 Aug 2021 19:38:16 +0200
Subject: [PATCH] Handle nulls in runtime upcast checks

---
 src/compiler.ts                           |  31 +++-
 tests/compiler/managed-cast.optimized.wat | 173 +++++++++++-----------
 tests/compiler/managed-cast.untouched.wat |  21 ++-
 3 files changed, 127 insertions(+), 98 deletions(-)

diff --git a/src/compiler.ts b/src/compiler.ts
index 0e0e06d405..5efd2fba16 100644
--- a/src/compiler.ts
+++ b/src/compiler.ts
@@ -10565,14 +10565,31 @@ export class Compiler extends DiagnosticEmitter {
     var temp = flow.getTempLocal(type);
     var instanceofInstance = this.program.instanceofInstance;
     assert(this.compileFunction(instanceofInstance));
-    expr = module.if(
-      module.call(instanceofInstance.internalName, [
+    if (!toType.isNullableReference || flow.isNonnull(expr, type)) {
+      // Simplify if the value cannot be `null`. If toType is non-nullable, a
+      // null-check would have been emitted separately so is not necessary here.
+      expr = module.if(
+        module.call(instanceofInstance.internalName, [
+          module.local_tee(temp.index, expr, type.isManaged),
+          module.i32(toType.classReference!.id)
+        ], TypeRef.I32),
+        module.local_get(temp.index, type.toRef()),
+        this.makeStaticAbort(this.ensureStaticString("unexpected upcast"), reportNode) // TODO: throw
+      );
+    } else {
+      expr = module.if(
         module.local_tee(temp.index, expr, type.isManaged),
-        module.i32(toType.classReference!.id)
-      ], TypeRef.I32),
-      module.local_get(temp.index, type.toRef()),
-      this.makeStaticAbort(this.ensureStaticString("unexpected upcast"), reportNode) // TODO: throw
-    );
+        module.if(
+          module.call(instanceofInstance.internalName, [
+            module.local_get(temp.index, type.toRef()),
+            module.i32(toType.classReference!.id)
+          ], TypeRef.I32),
+          module.local_get(temp.index, type.toRef()),
+          this.makeStaticAbort(this.ensureStaticString("unexpected upcast"), reportNode) // TODO: throw
+        ),
+        module.usize(0)
+      );
+    }
     flow.freeTempLocal(temp);
     this.currentType = toType;
     return expr;
diff --git a/tests/compiler/managed-cast.optimized.wat b/tests/compiler/managed-cast.optimized.wat
index 65555741cf..cd7df977b2 100644
--- a/tests/compiler/managed-cast.optimized.wat
+++ b/tests/compiler/managed-cast.optimized.wat
@@ -1468,17 +1468,17 @@
    i32.const 1344
    global.set $~lib/rt/itcms/fromSpace
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.get $1
+   local.get $0
    i32.store
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 4
    i32.sub
    global.set $~lib/memory/__stack_pointer
@@ -1489,7 +1489,7 @@
    global.get $~lib/memory/__stack_pointer
    i32.const 0
    i32.store
-   local.get $1
+   local.get $0
    i32.eqz
    if
     i32.const 1456
@@ -1500,30 +1500,30 @@
     unreachable
    end
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 4
    i32.add
    global.set $~lib/memory/__stack_pointer
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.get $1
+   local.get $0
    i32.store
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.get $1
+   local.get $0
    i32.store
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 4
    i32.sub
    global.set $~lib/memory/__stack_pointer
@@ -1535,29 +1535,29 @@
    i32.const 0
    i32.store
    block $__inlined_func$~lib/rt/__instanceof (result i32)
-    local.get $1
+    local.get $0
     i32.const 20
     i32.sub
     i32.load offset=12
-    local.tee $0
+    local.tee $1
     i32.const 1632
     i32.load
     i32.le_u
     if
      loop $do-continue|0
       i32.const 1
-      local.get $0
+      local.get $1
       i32.const 3
       i32.eq
       br_if $__inlined_func$~lib/rt/__instanceof
       drop
-      local.get $0
+      local.get $1
       i32.const 3
       i32.shl
       i32.const 1636
       i32.add
       i32.load offset=4
-      local.tee $0
+      local.tee $1
       br_if $do-continue|0
      end
     end
@@ -1573,20 +1573,20 @@
     unreachable
    end
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 4
    i32.add
    global.set $~lib/memory/__stack_pointer
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 8
    i32.sub
    global.set $~lib/memory/__stack_pointer
@@ -1595,10 +1595,10 @@
    i32.lt_s
    br_if $folding-inner0
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
+   local.tee $1
    i64.const 0
    i64.store
-   local.get $1
+   local.get $0
    i32.eqz
    if
     i32.const 1456
@@ -1608,11 +1608,12 @@
     call $~lib/builtins/abort
     unreachable
    end
-   local.get $0
    local.get $1
+   local.get $0
+   local.tee $1
    i32.store offset=4
    block $__inlined_func$~lib/rt/__instanceof11 (result i32)
-    local.get $1
+    local.get $0
     i32.const 20
     i32.sub
     i32.load offset=12
@@ -1658,12 +1659,12 @@
    i32.add
    global.set $~lib/memory/__stack_pointer
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 4
    i32.sub
    global.set $~lib/memory/__stack_pointer
@@ -1676,29 +1677,29 @@
    i32.const 0
    i32.store
    block $__inlined_func$~lib/rt/__instanceof14 (result i32)
-    local.get $1
+    local.get $0
     i32.const 20
     i32.sub
     i32.load offset=12
-    local.tee $0
+    local.tee $1
     i32.const 1632
     i32.load
     i32.le_u
     if
      loop $do-continue|015
       i32.const 1
-      local.get $0
+      local.get $1
       i32.const 3
       i32.eq
       br_if $__inlined_func$~lib/rt/__instanceof14
       drop
-      local.get $0
+      local.get $1
       i32.const 3
       i32.shl
       i32.const 1636
       i32.add
       i32.load offset=4
-      local.tee $0
+      local.tee $1
       br_if $do-continue|015
      end
     end
@@ -1714,19 +1715,19 @@
     unreachable
    end
    local.get $2
-   local.get $1
+   local.get $0
    i32.store
    global.get $~lib/memory/__stack_pointer
    i32.const 4
    i32.add
    global.set $~lib/memory/__stack_pointer
    call $managed-cast/Cat#constructor
-   local.set $1
+   local.set $0
    global.get $~lib/memory/__stack_pointer
-   local.tee $0
-   local.get $1
-   i32.store
+   local.tee $1
    local.get $0
+   i32.store
+   local.get $1
    i32.const 4
    i32.sub
    global.set $~lib/memory/__stack_pointer
@@ -1738,46 +1739,52 @@
    local.tee $2
    i32.const 0
    i32.store
-   block $__inlined_func$~lib/rt/__instanceof17 (result i32)
-    local.get $1
-    i32.const 20
-    i32.sub
-    i32.load offset=12
-    local.tee $0
-    i32.const 1632
-    i32.load
-    i32.le_u
-    if
-     loop $do-continue|018
-      i32.const 1
-      local.get $0
-      i32.const 3
-      i32.eq
-      br_if $__inlined_func$~lib/rt/__instanceof17
-      drop
-      local.get $0
-      i32.const 3
-      i32.shl
-      i32.const 1636
-      i32.add
-      i32.load offset=4
-      local.tee $0
-      br_if $do-continue|018
+   local.get $0
+   if
+    block $__inlined_func$~lib/rt/__instanceof17 (result i32)
+     local.get $0
+     i32.const 20
+     i32.sub
+     i32.load offset=12
+     local.tee $1
+     i32.const 1632
+     i32.load
+     i32.le_u
+     if
+      loop $do-continue|018
+       i32.const 1
+       local.get $1
+       i32.const 3
+       i32.eq
+       br_if $__inlined_func$~lib/rt/__instanceof17
+       drop
+       local.get $1
+       i32.const 3
+       i32.shl
+       i32.const 1636
+       i32.add
+       i32.load offset=4
+       local.tee $1
+       br_if $do-continue|018
+      end
      end
+     i32.const 0
     end
+    i32.eqz
+    if
+     i32.const 1584
+     i32.const 1520
+     i32.const 47
+     i32.const 30
+     call $~lib/builtins/abort
+     unreachable
+    end
+   else
     i32.const 0
-   end
-   i32.eqz
-   if
-    i32.const 1584
-    i32.const 1520
-    i32.const 47
-    i32.const 30
-    call $~lib/builtins/abort
-    unreachable
+    local.set $0
    end
    local.get $2
-   local.get $1
+   local.get $0
    i32.store
    global.get $~lib/memory/__stack_pointer
    i32.const 4
diff --git a/tests/compiler/managed-cast.untouched.wat b/tests/compiler/managed-cast.untouched.wat
index f5f059bbb6..d0a0bfe294 100644
--- a/tests/compiler/managed-cast.untouched.wat
+++ b/tests/compiler/managed-cast.untouched.wat
@@ -2469,17 +2469,22 @@
   global.get $~lib/memory/__stack_pointer
   local.get $0
   local.tee $1
-  i32.const 3
-  call $~lib/rt/__instanceof
   if (result i32)
    local.get $1
+   i32.const 3
+   call $~lib/rt/__instanceof
+   if (result i32)
+    local.get $1
+   else
+    i32.const 560
+    i32.const 496
+    i32.const 47
+    i32.const 30
+    call $~lib/builtins/abort
+    unreachable
+   end
   else
-   i32.const 560
-   i32.const 496
-   i32.const 47
-   i32.const 30
-   call $~lib/builtins/abort
-   unreachable
+   i32.const 0
   end
   local.tee $2
   i32.store