[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/arm/code-generator-arm.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/arm/macro-assembler-arm.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
@@ skipping 700 matching lines @@
       break;
     case kArmVsqrtF32:
       __ vsqrt(i.OutputFloat32Register(), i.InputFloat32Register(0));
       break;
     case kArmVabsF32:
       __ vabs(i.OutputFloat32Register(), i.InputFloat32Register(0));
       break;
     case kArmVnegF32:
       __ vneg(i.OutputFloat32Register(), i.InputFloat32Register(0));
       break;
+    case kArmVrintmF32:
+      __ vrintm(i.OutputFloat32Register(), i.InputFloat32Register(0));
+      break;
     case kArmVcmpF64:
       if (instr->InputAt(1)->IsDoubleRegister()) {
         __ VFPCompareAndSetFlags(i.InputFloat64Register(0),
                                  i.InputFloat64Register(1));
       } else {
         DCHECK(instr->InputAt(1)->IsImmediate());
         // 0.0 is the only immediate supported by vcmp instructions.
         DCHECK(i.InputDouble(1) == 0.0);
         __ VFPCompareAndSetFlags(i.InputFloat64Register(0), i.InputDouble(1));
       }
@@ skipping 621 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8