Convert SIMD wasm ops to runtime function calls

src/wasm/ast-decoder.cc

Index: src/wasm/ast-decoder.cc
diff --git a/src/wasm/ast-decoder.cc b/src/wasm/ast-decoder.cc
index 833b33538ab554b5fbc74bca4f1dc72c2c4d86eb..009cdc54f71bc390115480ea08e83435514c12cb 100644
--- a/src/wasm/ast-decoder.cc
+++ b/src/wasm/ast-decoder.cc
@@ -522,6 +522,8 @@ class WasmFullDecoder : public WasmDecoder {
         return builder_->Float32Constant(0);
       case kAstF64:
         return builder_->Float64Constant(0);
+      case kAstS128:
+        return builder_->DefaultS128Value();
       default:
         UNREACHABLE();
         return nullptr;
@@ -589,6 +591,14 @@ class WasmFullDecoder : public WasmDecoder {
     while (true) {  // decoding loop.
       unsigned len = 1;
       WasmOpcode opcode = static_cast<WasmOpcode>(*pc_);
+      if (opcode == kSimdPrefix) {
+        // TODO(gdeepti): Piggybacking on unop/binop works for now, but this
+        // should be its own function to be able to parse more complex opcodes.
+        len++;
+        byte simd_index = *(pc_ + 1);
+        opcode = static_cast<WasmOpcode>(opcode << 8 | simd_index);
+      }
+
       TRACE("  @%-6d #%02x:%-20s|", startrel(pc_), opcode,
             WasmOpcodes::ShortOpcodeName(opcode));