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Roman Lebedev cd9b19484b [Codegen][SelectionDAG] X u% C == 0 fold: non-splat vector improvements 
Summary:
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`,
   * https://godbolt.org/z/7jnZJX https://rise4fun.com/Alive/oF6p
   * 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: https://reviews.llvm.org/D63963

llvm-svn: 366637
 		2019-07-20 16:33:15 +00:00
clang Fix cppcheck reduce scope variable warnings. NFCI 2019-07-20 13:01:16 +00:00
clang-tools-extra [clangd] Provide a way to publish highlightings in non-racy manner 2019-07-19 13:51:01 +00:00
compiler-rt Revert "Fix asan infinite loop on undefined symbol" 2019-07-20 13:00:12 +00:00
debuginfo-tests Make nrvo-string test more robust. 2019-06-27 20:38:37 +00:00
libclc travis: Add LLVM-8 build 2019-03-27 21:28:31 +00:00
libcxx [libc++] Mark libcpp_deallocate.sh.cpp as UNSUPPORTED instead of XFAIL on AppleClang 9 2019-07-19 19:41:40 +00:00
libcxxabi Revert "[libc++] Integrate the PSTL into libc++" 2019-07-19 18:52:46 +00:00
libunwind [libunwind][ARM] Fix loading FP registers on big-endian targets 2019-07-19 15:20:32 +00:00
lld [WebAssembly] Compute and export TLS block alignment 2019-07-19 23:34:16 +00:00
lldb [CMake] Align debugserver with lldb-server on Darwin 2019-07-20 11:18:31 +00:00
llgo IR: Support parsing numeric block ids, and emit them in textual output. 2019-03-22 18:27:13 +00:00
llvm [Codegen][SelectionDAG] X u% C == 0 fold: non-splat vector improvements 2019-07-20 16:33:15 +00:00
openmp [OpenMP][libomptarget] Suppress C++ 11 related warnings when building libomptarget-nvptx bitcode library, by Doru Bercea. 2019-07-18 13:54:01 +00:00
parallel-libs Fix typos throughout the license files that somehow I and my reviewers 2019-01-21 09:52:34 +00:00
polly Update polly test for SCEV change. 2019-07-18 22:35:45 +00:00
pstl Revert "[libc++] Integrate the PSTL into libc++" 2019-07-19 18:52:46 +00:00
.arcconfig Update monorepo .arcconfig with new project callsign. 2019-01-31 14:34:59 +00:00
.clang-format Add .clang-tidy and .clang-format files to the toplevel of the 2019-01-29 16:43:16 +00:00
.clang-tidy Disable tidy checks with too many hits 2019-02-01 11:20:13 +00:00
.gitignore Add a reduced copy of the llvm .gitignore 2019-04-09 00:52:49 +00:00
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