Version 3.5.0-6.0.dev

Merge cc3b3f4 into dev

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

@@ -1172,6 +1172,18 @@ class SsaInstructionSimplifier extends HBaseVisitor<HInstruction>
     return super.visitAdd(node);
   }
 
+  @override
+  HInstruction visitSubtract(HSubtract node) {
+    HInstruction left = node.left;
+    HInstruction right = node.right;
+    if (right is HConstant) {
+      final constant = right.constant;
+      // Rewrite `a - 0` to `a`, provided the zero is not negative zero.
+      if (constant.isZero && !constant.isMinusZero) return left;
+    }
+    return super.visitSubtract(node);
+  }
+
   @override
   HInstruction visitMultiply(HMultiply node) {
     HInstruction left = node.left;

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

@@ -0,0 +1,115 @@
+// Copyright (c) 2024, 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.
+
+// Generally, we can replace `a - b` with `a` when `a` is a number and `b` is
+// zero.
+//
+// The exception is when both operands are negative zero: `(-0.0) - (-0.0)`
+// results in a non-negative zero.
+//
+// With web numbers, the value `-0.0` is recognized as an integer so can occur
+// as a constant right operand, usually by constant-folding.
+
+/*member: main:ignore*/
+void main() {
+  for (final a in [
+    C(),
+    0,
+    -0.0,
+    1,
+    -1,
+    1.1,
+    -1.1,
+    double.nan,
+    double.infinity,
+    double.negativeInfinity,
+  ]) {
+    sink.add(whenDynamic(a));
+
+    if (a is int) {
+      sink.add(whenInt1(a));
+      sink.add(whenInt2(a));
+    }
+    if (a is double) {
+      sink.add(whenDouble1(a));
+      sink.add(whenDouble2(a));
+    }
+    if (a is num) {
+      sink.add(whenNum1(a));
+      sink.add(whenNum2(a));
+      sink.add(whenNum3(a));
+    }
+  }
+}
+
+final List<Object?> sink = [];
+
+@pragma('dart2js:never-inline')
+/*member: whenDynamic:function(thing) {
+  return J.$sub$n(thing, 0);
+}*/
+whenDynamic(dynamic thing) {
+  return thing - 0;
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenInt1:function(a) {
+  return a;
+}*/
+int whenInt1(int a) {
+  return a - 0;
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenInt2:function(a) {
+  return a - -0.0;
+}*/
+int whenInt2(int a) {
+  return a - (-0);
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenDouble1:function(a) {
+  return a;
+}*/
+double whenDouble1(double a) {
+  return a - 0;
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenDouble2:function(a) {
+  return a - -0.0;
+}*/
+double whenDouble2(double a) {
+  return a - (-0.0);
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenNum1:function(a) {
+  return a;
+}*/
+num whenNum1(num a) {
+  return a - 0;
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenNum2:function(a) {
+  return a - -0.0;
+}*/
+num whenNum2(num a) {
+  return a - (-0);
+}
+
+@pragma('dart2js:never-inline')
+/*member: whenNum3:function(a) {
+  return a - -0.0;
+}*/
+num whenNum3(num a) {
+  return a - (-0.0);
+}
+
+class C {
+  /*member: C.-:ignore*/
+  C operator -(int i) => this;
+}

tools/VERSION

@@ -27,5 +27,5 @@ CHANNEL dev
 MAJOR 3
 MINOR 5
 PATCH 0
-PRERELEASE 5
+PRERELEASE 6
 PRERELEASE_PATCH 0