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Unverified Commit 0727e2b9 authored by Roman Lebedev's avatar Roman Lebedev
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[DAGCombiner][X86][AArch64] Generalize `A-(A&B)`->`A&(~B)` fold (PR44448)

The fold 'A - (A & (B - 1))' -> 'A & (0 - B)'
added in 8dab0a4a
is too specific. It should/can just be 'A - (A & B)' -> 'A & (~B)'

Even if we don't manage to fold `~` into B,
we have likely formed `ANDN` node.
Also, this way there's less similar-but-duplicate folds.

Name: X - (X & Y)  ->  X & (~Y)
%o = and i32 %X, %Y
%r = sub i32 %X, %o
  =>
%n = xor i32 %Y, -1
%r = and i32 %X, %n

https://rise4fun.com/Alive/kOUl

See
  https://bugs.llvm.org/show_bug.cgi?id=44448
  https://reviews.llvm.org/D71499
parent 473deaf3
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