[turbofan] More aggressive reuse of spill slots in the register allocator.

src/compiler/x64/code-generator-x64.cc

 // Copyright 2013 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/compiler/code-generator.h"
 
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties-inl.h"
@@ skipping 983 matching lines @@
     __ xchgq(tmp, src);
     __ movq(dst, tmp);
   } else if (source->IsDoubleRegister() && destination->IsDoubleRegister()) {
     // XMM register-register swap. We rely on having xmm0
     // available as a fixed scratch register.
     XMMRegister src = g.ToDoubleRegister(source);
     XMMRegister dst = g.ToDoubleRegister(destination);
     __ movsd(xmm0, src);
     __ movsd(src, dst);
     __ movsd(dst, xmm0);
-  } else if (source->IsDoubleRegister() && destination->IsDoubleRegister()) {
+  } else if (source->IsDoubleRegister() && destination->IsDoubleStackSlot()) {
     // XMM register-memory swap.  We rely on having xmm0
     // available as a fixed scratch register.
     XMMRegister src = g.ToDoubleRegister(source);
     Operand dst = g.ToOperand(destination);
     __ movsd(xmm0, src);
     __ movsd(src, dst);
     __ movsd(dst, xmm0);
   } else {
     // No other combinations are possible.
     UNREACHABLE();
@@ skipping 16 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace compiler
 }  // namespace v8