[turbofan] Introduce proper abstractions for ToNumber truncations.

test/cctest/compiler/test-code-stub-assembler.cc

 // Copyright 2015 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/interface-descriptors.h"
 #include "src/isolate.h"
 #include "test/cctest/compiler/function-tester.h"
 
 namespace v8 {
 namespace internal {
@@ skipping 301 matching lines @@
       parameter_count_with_receiver - 1);  // Implicit undefined receiver.
   return function;
 }
 
 }  // namespace
 
 TEST(JSFunction) {
   const int kNumParams = 3;  // Receiver, left, right.
   Isolate* isolate(CcTest::InitIsolateOnce());
   CodeStubAssemblerTester m(isolate, kNumParams);
-  m.Return(m.SmiTag(
-      m.Int32Add(m.SmiToInt32(m.Parameter(1)), m.SmiToInt32(m.Parameter(2)))));
+  m.Return(m.SmiTag(m.Int32Add(m.SmiToWord32(m.Parameter(1)),
+                               m.SmiToWord32(m.Parameter(2)))));
   Handle<Code> code = m.GenerateCode();
   Handle<JSFunction> function = CreateFunctionFromCode(kNumParams, code);
   Handle<Object> args[] = {Handle<Smi>(Smi::FromInt(23), isolate),
                            Handle<Smi>(Smi::FromInt(34), isolate)};
   MaybeHandle<Object> result =
       Execution::Call(isolate, function, isolate->factory()->undefined_value(),
                       arraysize(args), args);
   CHECK_EQ(57, Handle<Smi>::cast(result.ToHandleChecked())->value());
 }
 
@@ skipping 23 matching lines @@
   m.Goto(&l2);
   m.Bind(&l2);
   m.Goto(&default_label);
   m.Bind(&default_label);
   USE(m.GenerateCode());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8