MIPS: [turbofan] Support for %_DoubleHi, %_DoubleLo and %_ConstructDouble.

src/compiler/mips64/code-generator-mips64.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/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/mips/macro-assembler-mips.h"
 #include "src/scopes.h"
@@ skipping 667 matching lines @@
       __ trunc_w_d(scratch, i.InputDoubleRegister(0));
       __ mfc1(i.OutputRegister(), scratch);
       break;
     }
     case kMips64TruncUwD: {
       FPURegister scratch = kScratchDoubleReg;
       // TODO(plind): Fix wrong param order of Trunc_uw_d() macro-asm function.
       __ Trunc_uw_d(i.InputDoubleRegister(0), i.OutputRegister(), scratch);
       break;
     }
+    case kMips64FmoveLowUwD:
+      __ FmoveLow(i.OutputRegister(), i.InputDoubleRegister(0));
+      // remove sign.
+      __ li(at, Operand(32));
+      __ dsllv(i.OutputRegister(), i.OutputRegister(), at);
+      __ dsrlv(i.OutputRegister(), i.OutputRegister(), at);

[paul.l..., 2015/03/05 17:40:48]

You can avoid the load and use of 'at' register here by using:
__ dsll32(i.OutputRegister(), i.OutputRegister(), 0);
__ dsrl32(i.OutputRegister(), i.OutputRegister(), 0);

[balazs.kilvady, 2015/03/05 18:07:08]

Thanks, I modify it. Anyway test are passed without the 2 shifts I just added
them to ensure unsigned result. Could I drop it? 

[paul.l..., 2015/03/05 18:43:49]

Let's leave the shifts to strip sign extension for now, and re-check later.

+      break;
+    case kMips64FmoveLowDUw:
+      __ FmoveLow(i.OutputDoubleRegister(), i.InputRegister(1));
+      break;
+    case kMips64FmoveHighUwD:
+      __ FmoveHigh(i.OutputRegister(), i.InputDoubleRegister(0));
+      break;
+    case kMips64FmoveHighDUw:
+      __ FmoveHigh(i.OutputDoubleRegister(), i.InputRegister(1));
+      break;
     // ... more basic instructions ...
 
     case kMips64Lbu:
       __ lbu(i.OutputRegister(), i.MemoryOperand());
       break;
     case kMips64Lb:
       __ lb(i.OutputRegister(), i.MemoryOperand());
       break;
     case kMips64Sb:
       __ sb(i.InputRegister(2), i.MemoryOperand());
@@ skipping 667 matching lines @@
     }
   }
   MarkLazyDeoptSite();
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8