[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/raw-machine-assembler.h

Index: src/compiler/raw-machine-assembler.h
diff --git a/src/compiler/raw-machine-assembler.h b/src/compiler/raw-machine-assembler.h
index e4e6d01434f9fcc7473a3c2534206d1317c4301e..031d949036f7adbda1d6f70cd555fc6cde192860 100644
--- a/src/compiler/raw-machine-assembler.h
+++ b/src/compiler/raw-machine-assembler.h
@@ -483,6 +483,9 @@ class RawMachineAssembler {
   Node* BitcastInt64ToFloat64(Node* a) {
     return AddNode(machine()->BitcastInt64ToFloat64(), a);
   }
+  Node* Float32RoundDown(Node* a) {
+    return AddNode(machine()->Float32RoundDown().op(), a);
+  }
   Node* Float64RoundDown(Node* a) {
     return AddNode(machine()->Float64RoundDown().op(), a);
   }