[all-commits] [llvm/llvm-project] f2e42d: [mlir][IntRangeInference] Handle ceildivsi(INT_MIN...

[Krzysztof Drewniak via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f2e42d9324f488ef113b8d2157f52ef1699b95f9
      https://github.com/llvm/llvm-project/commit/f2e42d9324f488ef113b8d2157f52ef1699b95f9
  Author: Krzysztof Drewniak <Krzysztof.Drewniak at amd.com>
  Date:   2024-11-15 (Fri, 15 Nov 2024)

  Changed paths:
    M mlir/lib/Interfaces/Utils/InferIntRangeCommon.cpp
    M mlir/test/Dialect/Arith/int-range-interface.mlir

  Log Message:
  -----------
  [mlir][IntRangeInference] Handle ceildivsi(INT_MIN, x > 1) as expected (#116284)

Fixes #115293

While the definition of ceildivsi is integer division, rounding up, most
implementations will use `-(-a / b)` for dividing `a ceildiv b` with `a`
negative and `b` positive.

Mathematically, and for most integers, these two definitions are
equivalent. However, with `a == INT_MIN`, the initial negation is a
noop, which means that, while divinding and rounding up would give a
negative result, `-((- INT_MIN) / b)` is `-(INT_MIN / b)`, which is
positive.

This commit adds a special case to ceilDivSI inference to handle this
case and bring it in line with the operational instead of the
mathematical semantics of ceiling division.



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