[turbofan] Implemented the optional Float32RoundDown operator.

src/compiler/verifier.cc

Index: src/compiler/verifier.cc
diff --git a/src/compiler/verifier.cc b/src/compiler/verifier.cc
index 3b898ef8af24f1282d1466c4e74f58161077f5c0..a24b5b5d29aa9509cc0cde85ec9074c1bcecb227 100644
--- a/src/compiler/verifier.cc
+++ b/src/compiler/verifier.cc
@@ -888,6 +888,7 @@ void Verifier::Visitor::Check(Node* node) {
     case IrOpcode::kFloat64Min:
     case IrOpcode::kFloat64Abs:
     case IrOpcode::kFloat64Sqrt:
+    case IrOpcode::kFloat32RoundDown:
     case IrOpcode::kFloat64RoundDown:
     case IrOpcode::kFloat64RoundUp:
     case IrOpcode::kFloat64RoundTruncate: