Instead of doing the adjustment in 3 different places in the code
base, do it inside UnsignedDivideUsingMagic::get.
Differential Revision: https://reviews.llvm.org/D141014
The magic algorithm sets IsAdd indication for division by 1 that
the caller had to ignore.
I considered folding the ignore into UnsignedDivisionByConstantInfo,
but we only allow 1 for vectors of mixed visiors. And really what we
want to end up with is undef. Currently, we get to undef via
DemandedElts optimizations using the select instruction. We could
directly emit undef.
Differential Revision: https://reviews.llvm.org/D140940
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
While these functions are only used in one location in upstream,
it has been reused in multiple downstreams. Restore this file to
a globally visibile location (outside of APInt.h) to eliminate
donwstream breakage and enable potential future reuse.
Additionally, this patch renames types and cleans up
clang-tidy issues.
