[all-commits] [llvm/llvm-project] f4e42f: [SCEV] Merge udiv exact logic into general udiv lo...

[Nikita Popov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f4e42fb59b2474d368d2f0828a834a4aa32d82c4
      https://github.com/llvm/llvm-project/commit/f4e42fb59b2474d368d2f0828a834a4aa32d82c4
  Author: Nikita Popov <npopov at redhat.com>
  Date:   2026-05-07 (Thu, 07 May 2026)

  Changed paths:
    M llvm/lib/Analysis/ScalarEvolution.cpp
    M llvm/test/Analysis/ScalarEvolution/mul-udiv-folds.ll
    A llvm/test/Analysis/ScalarEvolution/udiv.ll

  Log Message:
  -----------
  [SCEV] Merge udiv exact logic into general udiv logic (#195840)

The udiv exact handling for constant RHS is already partially handling
in the generic udiv code:

https://github.com/llvm/llvm-project/blob/8a0c5d3f43b27c8e2895c6106d6b551d626979fd/llvm/lib/Analysis/ScalarEvolution.cpp#L3641-L3657

Move two remaining folds there as well:
 * `(%a * %b)<nuw> / %b` to `%a`
 * `(A*GCD * %b)<nuw> / (C*GCD)` to `(A * %b)<nuw> / C`

Removing common factors from a multiply does not require exact if the
multiply is nuw (and conversely, being exact is not sufficient without
nuw).

This makes getUDivExactExpr() equivalent to getUDivExpr(). I've retained
the method for now in case we want to add exact specific logic in the
future.

Proof: https://alive2.llvm.org/ce/z/iQeb6v



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