pengbins added inline comments. Herald added a subscriber: kristof.beyls.
================ Comment at: cfe/trunk/include/clang/Basic/arm_neon.td:377 +def OP_QRDMLAH : Op<(call "vqadd", $p0, (call "vqrdmulh", $p1, $p2))>; +def OP_QRDMLSH : Op<(call "vqsub", $p0, (call "vqrdmulh", $p1, $p2))>; +def OP_QRDMLAH_LN : Op<(call "vqadd", $p0, (call "vqrdmulh", $p1, (splat $p2, $p3)))>; ---------------- @labrinea It seems QRDMLSH(p0, p1, p2) is not equivelent to with vqsub( p0, vqrdmulh(p1, p2)). - QRDMLSH(p0, p1, p2) ``` accum = ((p0 << esize) - 2 * (p1 * p2) + rounding_const); ret = SignedSatQ(accum >> esize, esize); ``` //p0<< esize + rounding_const // - vqsub( p0, vqrdmulh(p1, p2)) ``` temp = SignedSatQ( (2 * (p1 * p2) + rounding_const) >> esize ); ret = SignedSat( p0 - temp); ``` //p0<< esize - rounding_const // Here is an example where the results are not same. vqrdmlshq_s16 ( -197, -512, 11040) = -24 vqsubq_s16( -197, vqrdmulhq_n_s16(-512, 11040)) = -25 Repository: rL LLVM CHANGES SINCE LAST ACTION https://reviews.llvm.org/D14982/new/ https://reviews.llvm.org/D14982 _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
