[turbofan] Add backend support for Float32Constant.

src/compiler/instruction-selector-impl.h

Index: src/compiler/instruction-selector-impl.h
diff --git a/src/compiler/instruction-selector-impl.h b/src/compiler/instruction-selector-impl.h
index d00109e296fd85813ecdd422aa43fcae33234411..b860bc5187130ced1ef8329036c7c78bfa5ed299 100644
--- a/src/compiler/instruction-selector-impl.h
+++ b/src/compiler/instruction-selector-impl.h
@@ -146,8 +146,10 @@ class OperandGenerator {
         return Constant(OpParameter<int32_t>(node));
       case IrOpcode::kInt64Constant:
         return Constant(OpParameter<int64_t>(node));
-      case IrOpcode::kNumberConstant:
+      case IrOpcode::kFloat32Constant:
+        return Constant(OpParameter<float>(node));
       case IrOpcode::kFloat64Constant:
+      case IrOpcode::kNumberConstant:
         return Constant(OpParameter<double>(node));
       case IrOpcode::kExternalConstant:
         return Constant(OpParameter<ExternalReference>(node));