[wasm] Implement 128-bit endian swap for simd type

src/compiler/wasm-compiler.cc

Index: src/compiler/wasm-compiler.cc
diff --git a/src/compiler/wasm-compiler.cc b/src/compiler/wasm-compiler.cc
index 158c70fc5c03d9e1489ace784e16d2aac5e48dc8..6150e731242dac9c7cf6a7d6a09f8df110fbe88a 100644
--- a/src/compiler/wasm-compiler.cc
+++ b/src/compiler/wasm-compiler.cc
@@ -1069,6 +1069,8 @@ static bool ReverseBytesSupported(MachineOperatorBuilder* m,
       return m->Word32ReverseBytes().IsSupported();
     case 8:
       return m->Word64ReverseBytes().IsSupported();
+    case 16:

[Clemens Hammacher, 2017/04/26 18:40:05]

You can merge this with the case for 4.

+      return m->Word32ReverseBytes().IsSupported();
     default:
       break;
   }
@@ -1102,6 +1104,9 @@ Node* WasmGraphBuilder::BuildChangeEndianness(Node* node, MachineType memtype,
       // No need to change endianness for byte size, return original node
       return node;
       break;
+    case MachineRepresentation::kSimd128:
+      DCHECK(ReverseBytesSupported(m, 4));

[Clemens Hammacher, 2017/04/26 18:40:05]

You meant 16, not 4. You can also use valueSizeInBytes here.

+      break;
     default:
       UNREACHABLE();
       break;
@@ -1124,6 +1129,21 @@ Node* WasmGraphBuilder::BuildChangeEndianness(Node* node, MachineType memtype,
       case 8:
         result = graph()->NewNode(m->Word64ReverseBytes().op(), value);
         break;
+      case 16: {
+        Node* byte_reversed_lanes[4];
+        result = value;
+        for (int lane = 0; lane < 4; lane++)

[bbudge, 2017/04/26 20:14:12]

use braces for this loop body

and below

+          byte_reversed_lanes[lane] = graph()->NewNode(
+              m->Word32ReverseBytes().op(),
+              graph()->NewNode(jsgraph()->machine()->I32x4ExtractLane(lane),
+                               value));
+        for (int lane = 0; lane < 4; lane++)
+          result =
+              graph()->NewNode(jsgraph()->machine()->I32x4ReplaceLane(lane),
+                               result, byte_reversed_lanes[3 - lane]);
+
+        break;
+      }
       default:
         UNREACHABLE();
     }