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    • Bob Wilson's avatar
      Fix a minor bug in DAGCombiner's folding of SELECT. Folding "select C, 0, 1" · c2dc7ee5
      Bob Wilson authored
      to "C ^ 1" is only valid when C is known to be either 0 or 1.  Most of the
      similar foldings in this function only handle "i1" types, but this one appears
      intentionally written to handle larger integer types.  If C has an integer
      type larger than "i1", this needs to check if the high bits of a boolean
      are known to be zero.  I also changed the comment to describe this folding as
      "C ^ 1" instead of "~C", since that is what the code does and since the latter
      would only be valid for "i1" types.  The good news is that most LLVM targets
      use TargetLowering::ZeroOrOneBooleanContent so this change will not disable
      the optimization; the bad news is that I've been unable to come up with a
      testcase to demonstrate the problem.
      
      I have also removed a "FIXME" comment for folding "select C, X, 0" to "C & X",
      since the code looks correct to me.  It could be made more aggressive by not
      limiting the type to "i1", but that would then require checking for
      TargetLowering::ZeroOrNegativeOneBooleanContent.  Similar changes could be
      done for the other SELECT foldings, but it was decided to be not worth the
      trouble and complexity (see e.g., r44663).
      
      llvm-svn: 62790
      c2dc7ee5
    • Dan Gohman's avatar
      Don't create ISD::FNEG nodes after legalize if they aren't legal. · 1f3411de
      Dan Gohman authored
      Simplify x+0 to x in unsafe-fp-math mode. This avoids a bunch of
      redundant work in many cases, because in unsafe-fp-math mode,
      ISD::FADD with a constant is considered free to negate, so the
      DAGCombiner often negates x+0 to -0-x thinking it's free, when
      in reality the end result is -x, which is more expensive than x.
      
      Also, combine x*0 to 0.
      
      This fixes PR3374.
      
      llvm-svn: 62789
      1f3411de
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