[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/machine-operator.cc

Index: src/compiler/machine-operator.cc
diff --git a/src/compiler/machine-operator.cc b/src/compiler/machine-operator.cc
index 1fd6187f8faf21639550e393810e7df98605f273..6a9210b1965d3f653048f74a217e2fc16c6364c8 100644
--- a/src/compiler/machine-operator.cc
+++ b/src/compiler/machine-operator.cc
@@ -186,6 +186,7 @@ CheckedStoreRepresentation CheckedStoreRepresentationOf(Operator const* op) {
   V(Float32Min, Operator::kNoProperties, 2, 0, 1)           \
   V(Float64Max, Operator::kNoProperties, 2, 0, 1)           \
   V(Float64Min, Operator::kNoProperties, 2, 0, 1)           \
+  V(Float32RoundDown, Operator::kNoProperties, 1, 0, 1)     \
   V(Float64RoundDown, Operator::kNoProperties, 1, 0, 1)     \
   V(Float64RoundUp, Operator::kNoProperties, 1, 0, 1)       \
   V(Float64RoundTruncate, Operator::kNoProperties, 1, 0, 1) \