[all-commits] [llvm/llvm-project] 9735c0: [ValueTracking] Compute KnownFP state from recursi...

[David Green via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 9735c0518677a40d44cfd730d48d44bd29d0e9d7
      https://github.com/llvm/llvm-project/commit/9735c0518677a40d44cfd730d48d44bd29d0e9d7
  Author: David Green <david.green at arm.com>
  Date:   2024-10-31 (Thu, 31 Oct 2024)

  Changed paths:
    M llvm/lib/Analysis/ValueTracking.cpp
    M llvm/test/Transforms/Attributor/nofpclass-phiselect.ll
    M llvm/test/Transforms/LoopVectorize/ARM/mve-selectandorcost.ll
    M llvm/test/Transforms/PhaseOrdering/AArch64/predicated-reduction.ll

  Log Message:
  -----------
  [ValueTracking] Compute KnownFP state from recursive select/phi. (#113686)

Given a recursive phi with select:
 %p = phi [ 0, entry ], [ %sel, loop]
 %sel = select %c, %other, %p

The fp state can be calculated using the knowledge that the select/phi
pair can only be the initial state (0 here) or from %other. This adds a
short-cut into computeKnownFPClass for PHI to detect that the select is
recursive back to the phi, and if so use the state from the other
operand.

This helps to address a regression from #83200.



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