Started 7 mo 2 days ago
Took 37 min on green-dragon-03

Success Build rL:366637 - C:366635 - #63385 (Jul 20, 2019 9:36:03 AM)

  • : 366637
  • : 366635
  1. [Codegen][SelectionDAG] X u% C == 0 fold: non-splat vector improvements

    Four things here:
    1. Generalize the fold to handle non-splat divisors. Reasonably trivial.
    2. Unban power-of-two divisors. I don't see any reason why they should
       be illegal.
       * There is no ban in Hacker's Delight
       * I think the ban came from the same bug that caused the miscompile
          in the base patch - in `floor((2^W - 1) / D)` we were dividing by
          `D0` instead of `D`, and we **were** ensuring that `D0` is not `1`,
          which made sense.
    3. Unban `1` divisors. I no longer believe Hacker's Delight actually says
       that the fold is invalid for `D = 0`. Further considerations:
       * We know that
         * `(X u% 1) == 0`  can be constant-folded to `1`,
         * `(X u% 1) != 0`  can be constant-folded to `0`,
       *  Also, we know that
         * `X u<= -1` can be constant-folded to `1`,
         * `X u>  -1` can be constant-folded to `0`,
       * We know will end up with the following:
           `(setule/setugt (rotr (mul N, P), K), Q)`
       * Therefore, for given new DAG nodes and comparison predicates
         (`ule`/`ugt`), we will still produce the correct answer if:
         `Q` is a all-ones constant; and both `P` and `K` are *anything*
         other than `undef`.
       * The fold will indeed produce `Q = all-ones`.
    4. Try to re-splat the `P` and `K` vectors - we don't care about
       their values for the lanes where divisor was `1`.

    Reviewers: RKSimon, hermord, craig.topper, spatel, xbolva00

    Reviewed By: RKSimon

    Subscribers: hiraditya, javed.absar, dexonsmith, llvm-commits

    Tags: #llvm

    Differential Revision: (detail/ViewSVN)
    by lebedevri

Started by an SCM change (2 times)

This run spent:

  • 23 min waiting;
  • 37 min build duration;
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LLVM/Clang Warnings: 0 warnings.
  • No warnings since build 63,384.
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Test Result (no failures)