[PATCH] D47735: [DAGCombiner] Create rotates more aggressively

[Krzysztof Parzyszek via Phabricator via llvm-commits]

kparzysz added a comment.

One goal was to be able to generate rol-and-accumulate instruction (on Hexagon), specifically for the accumulate operation being | (see `f11` in rotate.ll).  For the C code we still don't generate it:

  unsigned blah(unsigned x, unsigned s) {
    return s | (x << 27) | (x >> 5);
  }

Using `clang -S -target hexagon -O2 fs.c -o -` gives

  {
          r0 |= asl(r1,#25)
  }
  {
          r0 |= lsr(r1,#7)
          jumpr r31
  }

What we'd want is `r0 |= rol(r1,#7)`.


Repository:
  rL LLVM

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  https://reviews.llvm.org/D47735/new/

https://reviews.llvm.org/D47735