Improve optimization of int & 0xFFFFFFFF.

Recognize a second operand if its `ToUint32` is `0xFFFFFFFF`,
not just the exact value. This includes fx `& -1`, which is output
by `toUnsigned(32)`.

Change-Id: Ieccb42591efd72b4aae62a7c6e678f05510abdc6
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/510960
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Lasse Nielsen <lrn@google.com>

pkg/compiler/lib/src/ssa/optimize.dart

@@ -2847,7 +2847,8 @@ class SsaInstructionSimplifier extends HBaseVisitor<HInstruction>
   }
 
   bool _isFull32BitMask(ConstantValue constant) {
-    return constant is IntConstantValue && constant.intValue == _mask32;
+    return constant is IntConstantValue &&
+        constant.intValue.toUnsigned(32) == _mask32;
   }
 
   static final _mask32 = BigInt.parse('FFFFFFFF', radix: 16);

pkg/compiler/test/codegen/data/bitand.dart

@@ -0,0 +1,49 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+// Data for a `../codegen_shard*_test.dart` test.
+
+/*member: main:ignore*/
+void main() {
+  for (var a in [0x123456789, 0, -2]) {
+    sink = recognizeMask32(a);
+    sink = recognizeMaskToUint32(a);
+    sink = recognizeNegativeMaskToUint32(a);
+    sink = recognizeAndFromToUnsigned(a);
+  }
+}
+
+Object? sink;
+
+@pragma('dart2js:noInline')
+/*member: recognizeMask32:function(thing) {
+  return thing >>> 0;
+}*/
+int recognizeMask32(int thing) {
+  return thing & 0xFFFF_FFFF;
+}
+
+@pragma('dart2js:noInline')
+/*member: recognizeMaskToUint32:function(thing) {
+  return thing >>> 0;
+}*/
+int recognizeMaskToUint32(int thing) {
+  return thing & 0xFFFF_FFFF_FFFF;
+}
+
+@pragma('dart2js:noInline')
+/*member: recognizeNegativeMaskToUint32:function(thing) {
+  return thing >>> 0;
+}*/
+int recognizeNegativeMaskToUint32(int thing) {
+  return thing & -1;
+}
+
+@pragma('dart2js:noInline')
+/*member: recognizeAndFromToUnsigned:function(thing) {
+  return thing >>> 0;
+}*/
+int recognizeAndFromToUnsigned(int thing) {
+  return thing.toUnsigned(32);
+}