[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/opcodes.h

 // 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.
 
 #ifndef V8_COMPILER_OPCODES_H_
 #define V8_COMPILER_OPCODES_H_
 
 #include <iosfwd>
 
 // Opcodes for control operators.
@@ skipping 276 matching lines @@
   V(BitcastInt32ToFloat32)      \
   V(BitcastInt64ToFloat64)      \
   V(Float32Add)                 \
   V(Float32Sub)                 \
   V(Float32Mul)                 \
   V(Float32Div)                 \
   V(Float32Max)                 \
   V(Float32Min)                 \
   V(Float32Abs)                 \
   V(Float32Sqrt)                \
+  V(Float32RoundDown)           \
   V(Float64Add)                 \
   V(Float64Sub)                 \
   V(Float64Mul)                 \
   V(Float64Div)                 \
   V(Float64Mod)                 \
   V(Float64Max)                 \
   V(Float64Min)                 \
   V(Float64Abs)                 \
   V(Float64Sqrt)                \
   V(Float64RoundDown)           \
@@ skipping 87 matching lines @@
   }
 };
 
 std::ostream& operator<<(std::ostream&, IrOpcode::Value);
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_OPCODES_H_