[wasm] Implement simd lowering for I16x8

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 70186fdf11d4283868f8215bbab12e4908428493..60c10c5321004fa858f8711b5f0f249c130b9eee 100644
--- a/src/compiler/simd-scalar-lowering.h
+++ b/src/compiler/simd-scalar-lowering.h
@@ -28,14 +28,23 @@ class SimdScalarLowering {
  private:
   enum class State : uint8_t { kUnvisited, kOnStack, kVisited };
 
-  enum class SimdType : uint8_t { kInt32, kFloat32, kSimd1x4 };
+  enum class SimdType : uint8_t {
+    kFloat32,
+    kInt32,
+    kInt16,
+    kSimd1x4,

[bbudge, 2017/04/27 18:03:42]

It's strange to see lane types (e.g. kFloat32) mixed with SIMD types here. I
think you could eliminate the boolean vector types, and just use the lane type,
so instead of kSimd1x4 it could be kInt32. I'm assuming you're treating boolean
vectors as a bunch of integers, and not as bit masks.

[aseemgarg, 2017/04/28 20:50:41]

We do need the various types. Basically, this is to ensure that Int32x4 is not
mixed with Simd1x4 (even though boolean types are implemented using int32). But
I guess the naming would be better if I used kInt32x4 instead of kInt32 and so
on. Made the change.

+    kSimd1x8
+  };

[bbudge, 2017/04/27 18:03:42]

On further thought, is this enum really needed? Could you use
MachineRepresentation? I don't see any need to distinguish the boolean vector
types.

[aseemgarg, 2017/04/28 20:50:41]

Machine representation won't work as we need to distinguish between the various
Simd128 types.

 
-  static const int kMaxLanes = 4;
-  static const int kLaneWidth = 16 / kMaxLanes;
+  static const int kNumLanes32 = 4;
+  static const int kNumLanes16 = 8;
+  static const int32_t kMask16 = 0xffff;
+  static const int32_t kShift16 = 16;

[bbudge, 2017/04/27 18:03:42]

Define these in the .cc file in an anonymous namespace.

[aseemgarg, 2017/04/28 20:50:41]

Done.

 
   struct Replacement {
-    Node* node[kMaxLanes];
-    SimdType type;  // represents what input type is expected
+    Node** node;
+    SimdType type;  // represents output type
+    int num_replacements;
   };
 
   struct NodeState {
@@ -52,24 +61,37 @@ class SimdScalarLowering {
   void LowerNode(Node* node);
   bool DefaultLowering(Node* node);
 
-  void ReplaceNode(Node* old, Node** new_nodes);
+  int NumLanes(SimdType type);
+  void ReplaceNode(Node* old, Node** new_nodes, int count);
   bool HasReplacement(size_t index, Node* node);
   Node** GetReplacements(Node* node);
+  int ReplacementCount(Node* node);
+  void Float32ToInt32(Node** replacements, Node** result);
+  void Int32ToFloat32(Node** replacements, Node** result);
+  void Int32ToInt16(Node** replacements, Node** result);
+  void Int16ToInt32(Node** replacements, Node** result);
   Node** GetReplacementsWithType(Node* node, SimdType type);
   SimdType ReplacementType(Node* node);
   void PreparePhiReplacement(Node* phi);
   void SetLoweredType(Node* node, Node* output);
-  void GetIndexNodes(Node* index, Node** new_indices);
+  void GetIndexNodes(Node* index, Node** new_indices, SimdType type);
   void LowerLoadOp(MachineRepresentation rep, Node* node,
-                   const Operator* load_op);
+                   const Operator* load_op, SimdType type);
   void LowerStoreOp(MachineRepresentation rep, Node* node,
                     const Operator* store_op, SimdType rep_type);
   void LowerBinaryOp(Node* node, SimdType input_rep_type, const Operator* op,
                      bool invert_inputs = false);
+  Node* FixUpperBits(Node* input, int32_t shift);
+  void LowerBinaryOpForSmallInt(Node* node, SimdType input_rep_type,
+                                const Operator* op);
+  Node* Mask(Node* input, int32_t mask);
+  void LowerSaturateBinaryOp(Node* node, SimdType input_rep_type,
+                             const Operator* op, bool is_signed);
   void LowerUnaryOp(Node* node, SimdType input_rep_type, const Operator* op);
-  void LowerIntMinMax(Node* node, const Operator* op, bool is_max);
+  void LowerIntMinMax(Node* node, const Operator* op, bool is_max,
+                      SimdType type);
   void LowerConvertFromFloat(Node* node, bool is_signed);
-  void LowerShiftOp(Node* node, const Operator* op);
+  void LowerShiftOp(Node* node, SimdType type);
   Node* BuildF64Trunc(Node* input);
   void LowerNotEqual(Node* node, SimdType input_rep_type, const Operator* op);