X87: [turbofan] Enable concurrent (re)compilation.

  port ff19726d (r35818)

  original commit message:
  Refactor the TurboFan pipeline to allow for concurrent recompilation in
  the same way that Crankshaft does it. For now we limit the concurrent
  phases to scheduling, instruction selection, register allocation and
  jump threading.

BUG=

Review-Url: https://codereview.chromium.org/1926383002
Cr-Commit-Position: refs/heads/master@{#35888}

src/compiler/x87/instruction-selector-x87.cc

@@ -64,11 +64,16 @@ class X87OperandGenerator final : public OperandGenerator {
       case IrOpcode::kRelocatableInt64Constant:
         return true;
       case IrOpcode::kHeapConstant: {
+// TODO(bmeurer): We must not dereference handles concurrently. If we
+// really have to this here, then we need to find a way to put this
+// information on the HeapConstant node already.
+#if 0
         // Constants in new space cannot be used as immediates in V8 because
         // the GC does not scan code objects when collecting the new generation.
         Handle<HeapObject> value = OpParameter<Handle<HeapObject>>(node);
         Isolate* isolate = value->GetIsolate();
         return !isolate->heap()->InNewSpace(*value);
+#endif
       }
       default:
         return false;