[all-commits] [llvm/llvm-project] f56ddd: [ARM] Restore hasSideEffects flag on t2WhileLoopSe...

[Sergei Barannikov via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: f56ddde410cd143792ce165958bc42fdcc9f7bb5
      https://github.com/llvm/llvm-project/commit/f56ddde410cd143792ce165958bc42fdcc9f7bb5
  Author: Sergei Barannikov <barannikov88 at gmail.com>
  Date:   2025-11-21 (Fri, 21 Nov 2025)

  Changed paths:
    M llvm/lib/Target/ARM/ARMInstrThumb2.td
    A llvm/test/CodeGen/Thumb2/LowOverheadLoops/pr168209.ll

  Log Message:
  -----------
  [ARM] Restore hasSideEffects flag on t2WhileLoopSetup (#168948)

ARM relies on deprecated TableGen behavior of guessing instruction
properties from patterns (`def ARM : Target` doesn't have
`guessInstructionProperties` set to false).

Before #168209, TableGen conservatively guessed that `t2WhileLoopSetup`
has side effects because the instruction wasn't matched by any pattern.

After the patch, TableGen guesses it has no side effects because the
added pattern uses only `arm_wlssetup` node, which has no side effects.

Add `SDNPSideEffect` to the node so that TableGen guesses the property
right, and also `hasSideEffects = 1` to the instruction in case ARM ever
sets `guessInstructionProperties` to false.



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