llvm dev - Dec 2019 - reg getInductionVariable

Hi,

The function getInductionVariable mandates the loop to be in
"SimplifyForm".

Loop::getInductionVariable(ScalarEvolution &SE) {
  if (!isLoopSimplifyForm())
    return nullptr;
  ...
  ...
}

bool Loop::isLoopSimplifyForm() {
   return getLoopPreheader() && getLoopLatch() &&
hasDedicatedExits();
}

/// Return true if no exit block for the loop has a predecessor that is
/// outside the loop.
bool hasDedicatedExits() const;

Is it necessary for the loop to have *DedicatedExists *to find the
induction variable?
Can this condition be relaxed?

-- 
Regards,
DTharun
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On 12/14, Dangeti Tharun kumar via llvm-dev wrote:
> The function getInductionVariable mandates the loop to be in
"SimplifyForm".
> 
> Is it necessary for the loop to have *DedicatedExists *to find the
> induction variable?
> Can this condition be relaxed?
Potentially, but it is often simpler to force simplified form. If need
dedicated exists, split the exiting edges of a loop. That will create
dedicated exist blocks.


Cheers,
  Johannes
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