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

Port f84f45f9

Original commit message:
When zeroing a floating point stack slot, store the zero register directly,
rather than storing zero moved to an FP register.

BUG=

Review-Url: https://codereview.chromium.org/2364903002
Cr-Commit-Position: refs/heads/master@{#39906}

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

@@ -2063,9 +2063,14 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
     } 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());
       }

src/compiler/mips64/code-generator-mips64.cc

@@ -2386,9 +2386,14 @@ void CodeGenerator::AssembleMove(InstructionOperand* source,
     } 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());
       }