[Bug 15771] New: Extending scops to handle loops with unknown (parametric) trip count

[bugzill...@llvm.org]

Bug ID	15771
Summary	Extending scops to handle loops with unknown (parametric) trip count
Product	Projects
Version	unspecified
Hardware	Other
OS	Linux
Status	NEW
Severity	normal
Priority	P
Component	Polly
Assignee	poll...@googlegroups.com
Reporter	sp...@codeaurora.org
Classification	Unclassified

The following testcase

int A[100];
void foo(int n) { 
  for (int i = 0, j = 0; i < n; i+=2, j++)
    A[j] += 1;
}

is not recognized as a valid scop: -debug-only=polly-detect prints:

Checking region: entry => <Function Return>
    Top level region is invalid
Checking region: entry.split => for.end
    Non affine loop bound '***COULDNOTCOMPUTE***' in loop: for.body
Checking region: for.body => for.cond.for.end_crit_edge
    Non affine loop bound '***COULDNOTCOMPUTE***' in loop: for.body

And this corresponds to this code:

  // Is the loop count affine?
  const SCEV *LoopCount = SE->getBackedgeTakenCount(L);
  if (!isAffineExpr(&Context.CurRegion, LoopCount, *SE))
    INVALID(LoopBound,
            "Non affine loop bound '"
                << *LoopCount << "' in loop: " << L->getHeader()->getName());

I think that unknown loop trip counts could be handled by adding a new
parameter.

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[bugzill...@llvm.org]

Johannes Doerfert changed bug 15771

What	Removed	Added
Status	NEW	RESOLVED
CC		doer...@cs.uni-saarland.de
Resolution	---	FIXED

Comment # 5 on bug 15771 from Johannes Doerfert

Fixed with the new domain generation and test case added in r248668.