RFR: 8329077: C2 SuperWord: Add MoveD2L, MoveL2D, MoveF2I, MoveI2F

[Bhavana Kilambi]

On Thu, 24 Jul 2025 10:29:15 GMT, Galder Zamarreño <galder at openjdk.org> wrote:

> I've added support to vectorize `MoveD2L`, `MoveL2D`, `MoveF2I` and `MoveI2F` nodes. The implementation follows a similar pattern to what is done with conversion (`Conv*`) nodes. The tests in `TestCompatibleUseDefTypeSize` have been updated with the new expectations.
> 
> Also added a JMH benchmark which measures throughput (the higher the number the better) for methods that exercise these nodes. On darwin/aarch64 it shows:
> 
> 
> Benchmark                                (seed)  (size)   Mode  Cnt      Base      Patch   Units   Diff
> VectorBitConversion.doubleToLongBits          0    2048  thrpt    8  1168.782   1157.717  ops/ms    -1%
> VectorBitConversion.doubleToRawLongBits       0    2048  thrpt    8  3999.387   7353.936  ops/ms   +83%
> VectorBitConversion.floatToIntBits            0    2048  thrpt    8  1200.338   1188.206  ops/ms    -1%
> VectorBitConversion.floatToRawIntBits         0    2048  thrpt    8  4058.248  14792.474  ops/ms  +264%
> VectorBitConversion.intBitsToFloat            0    2048  thrpt    8  3050.313  14984.246  ops/ms  +391%
> VectorBitConversion.longBitsToDouble          0    2048  thrpt    8  3022.691   7379.360  ops/ms  +144%
> 
> 
> The improvements observed are a result of vectorization. The lack of vectorization in `doubleToLongBits` and `floatToIntBits` demonstrates that these changes do not affect their performance. These methods do not vectorize because of flow control.
> 
> I've run the tier1-3 tests on linux/aarch64 and didn't observe any regressions.

src/hotspot/share/opto/vectornode.cpp line 1831:

> 1829: 
> 1830: bool VectorReinterpretNode::implemented(int opc, uint vlen, BasicType src_type, BasicType dst_type) {
> 1831:   if ((src_type == T_FLOAT && dst_type == T_INT) ||

Just a suggestion, do you feel a `switch-case` could be more readable/clear in this case? Something like this -


bool VectorReinterpretNode::implemented(uint vlen, BasicType src_type, BasicType dst_type) {
  switch (src_type) {
    case T_FLOAT:
      if (dst_type != T_INT)    return false;
      break;
    case T_INT:
      if (dst_type != T_FLOAT)  return false;
      break;
    case T_DOUBLE:
      if (dst_type != T_LONG)   return false;
      break;
    case T_LONG:
      if (dst_type != T_DOUBLE) return false;
      break;
    default:
      return false;
  }
  return Matcher::match_rule_supported_auto_vectorization(Op_VectorReinterpret, vlen, dst_type);
}

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/26457#discussion_r2247906630