Sanjay Patel 38ca7face6 [InstSimplify] reduce logic with inverted add/sub ops ...

https://llvm.org/PR48559
This could be part of a larger ValueTracking API,
but I don't see that currently.

https://rise4fun.com/Alive/gR0

  Name: and
  Pre: C1 == ~C2
  %sub = add i8 %x, C1
  %sub1 = sub i8 C2, %x
  %r = and i8 %sub, %sub1
  =>
  %r = 0

  Name: or
  Pre: C1 == ~C2
  %sub = add i8 %x, C1
  %sub1 = sub i8 C2, %x
  %r = or i8 %sub, %sub1
  =>
  %r = -1

  Name: xor
  Pre: C1 == ~C2
  %sub = add i8 %x, C1
  %sub1 = sub i8 C2, %x
  %r = xor i8 %sub, %sub1
  =>
  %r = -1

2020-12-21 08:51:43 -05:00

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