MIPS: Port [turbofan] ARM64: Use zr for zeroing stack slots

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/compilation-info.h"
 #include "src/compiler/code-generator-impl.h"
 #include "src/compiler/gap-resolver.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/osr.h"
@@ skipping 2367 matching lines @@
           break;
         }
         case Constant::kRpoNumber:
           UNREACHABLE();  // TODO(titzer): loading RPO numbers on mips64.
           break;
       }
       if (destination->IsStackSlot()) __ sd(dst, g.ToMemOperand(destination));
     } else if (src.type() == Constant::kFloat32) {
       if (destination->IsFPStackSlot()) {
         MemOperand dst = g.ToMemOperand(destination);
-        __ li(at, Operand(bit_cast<int32_t>(src.ToFloat32())));
-        __ sw(at, dst);
+        if (bit_cast<int32_t>(src.ToFloat32()) == 0) {
+          __ sw(zero_reg, dst);
+        } else {
+          __ li(at, Operand(bit_cast<int32_t>(src.ToFloat32())));
+          __ sw(at, dst);
+        }
       } else {
+        DCHECK(destination->IsFPRegister());
         FloatRegister dst = g.ToSingleRegister(destination);
         __ Move(dst, src.ToFloat32());
       }
     } else {
       DCHECK_EQ(Constant::kFloat64, src.type());
       DoubleRegister dst = destination->IsFPRegister()
                                ? g.ToDoubleRegister(destination)
                                : kScratchDoubleReg;
       __ Move(dst, src.ToFloat64());
       if (destination->IsFPStackSlot()) {
@@ skipping 118 matching lines @@
       padding_size -= v8::internal::Assembler::kInstrSize;
     }
   }
 }
 
 #undef __
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8