[PATCH] D48283: [SCEV] Properly solve quadratic equations

[Krzysztof Parzyszek via Phabricator via llvm-commits]

kparzysz marked 4 inline comments as done.
kparzysz added inline comments.


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Comment at: include/llvm/ADT/APInt.h:2178
+/// same time "allowing" subtraction. In unsigned modulo arithmetic a
+/// subtraction would always count as an overflow, but here we want to
+/// allow values to decrease and increase as long as they are within
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sanjoy wrote:
> I'm not sure this is correct -- `sub 5, 1` does not unsign-overflow right?  (since zext(5) - zext(1) == zext(5 - 1))?
That's true, but then `sub 5, 1` is not the same as `add 5, -1`. I'm treating `sub x, y` as equivalent to `add x, -y`. I added a comment explaining this.


Repository:
  rL LLVM

https://reviews.llvm.org/D48283