[wasm]implement simd lowering for f32x4->i32x4, i32x4 min/max and shift instructions

src/compiler/simd-scalar-lowering.h

Index: src/compiler/simd-scalar-lowering.h
diff --git a/src/compiler/simd-scalar-lowering.h b/src/compiler/simd-scalar-lowering.h
index 04f9d0ff77ca2dc6f2c4438a31e8ff807a99210b..2b8537829b9f2f406a313383861f9d15e40853da 100644
--- a/src/compiler/simd-scalar-lowering.h
+++ b/src/compiler/simd-scalar-lowering.h
@@ -61,6 +61,9 @@ class SimdScalarLowering {
                     const Operator* store_op, SimdType rep_type);
   void LowerBinaryOp(Node* node, SimdType input_rep_type, const Operator* op);
   void LowerUnaryOp(Node* node, SimdType input_rep_type, const Operator* op);
+  void LowerIntMinMax(Node* node, const Operator* op, bool is_max);
+  void LowerConvertFromFloat(Node* node, bool is_signed);
+  void LowerShiftOp(Node* node, const Operator* op);
 
   struct NodeState {
     Node* node;