[turbofan] Canonicalize x - K to x + -K.

test/unittests/compiler/machine-operator-reducer-unittest.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/base/bits.h"
 #include "src/base/division-by-constant.h"
 #include "src/compiler/js-graph.h"
 #include "src/compiler/machine-operator-reducer.h"
 #include "src/compiler/typer.h"
 #include "test/unittests/compiler/graph-unittest.h"
@@ skipping 824 matching lines @@
         Int32Constant(x));
     Reduction r = Reduce(node);
     ASSERT_TRUE(r.Changed());
     int32_t m = bit_cast<int32_t>(~((1U << x) - 1U));
     EXPECT_THAT(r.replacement(), IsWord32And(p0, IsInt32Constant(m)));
   }
 }
 
 
 // -----------------------------------------------------------------------------
+// Int32Sub
+
+
+TEST_F(MachineOperatorReducerTest, Int32SubWithConstant) {
+  Node* const p0 = Parameter(0);
+  TRACED_FOREACH(int32_t, k, kInt32Values) {
+    Reduction const r =
+        Reduce(graph()->NewNode(machine()->Int32Sub(), p0, Int32Constant(k)));
+    ASSERT_TRUE(r.Changed());
+    if (k == 0) {
+      EXPECT_EQ(p0, r.replacement());
+    } else {
+      EXPECT_THAT(r.replacement(), IsInt32Add(p0, IsInt32Constant(-k)));
+    }
+  }
+}
+
+
+// -----------------------------------------------------------------------------
 // Int32Div
 
 
 TEST_F(MachineOperatorReducerTest, Int32DivWithConstant) {
   Node* const p0 = Parameter(0);
   {
     Reduction const r = Reduce(graph()->NewNode(
         machine()->Int32Div(), p0, Int32Constant(0), graph()->start()));
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(), IsInt32Constant(0));
@@ skipping 519 matching lines @@
     Reduction r = Reduce(node);
     ASSERT_TRUE(r.Changed());
     EXPECT_THAT(r.replacement(),
                 IsStore(rep, base, index, value, effect, control));
   }
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8