[Support] Fix what I think is an off by 1 bug in UnsignedDivisionByConstantInfo.
The code in Hacker's Delight says `nc = -1 - (-d)%d;` But we have `NC = AllOnes - (AllOnes-D)%D` The Hacker's Delight code is written for the LeadingZeros==0 case. `AllOnes - D` is not the same as `-d` from Hacker's Delight. This patch changes the code to `NC = AllOnes - (AllOnes+1-D)%D` This will increment AllOnes to 0 in the LeadingZeros==0 case. This will make it equivalent to -D. I believe this is also correct for LeadingZeros>0. At least for i8, i16, and i32 the only divisor that changes is ((1 << (BitWidth-1)) | 1). Or 127 for i8, 32769 for i16, and 2147483649 for i32. These are all large enough that the quotient is 0 or 1 so InstCombine replaces them with an icmp and zext before SelectionDAG. Reviewed By: lebedev.ri Differential Revision: https://reviews.llvm.org/D140636
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