[llvm-commits] [llvm] r154007 - /llvm/trunk/lib/Transforms/Scalar/LoopUnrollPass.cpp

Hongbin Zheng etherzhhb at gmail.com
Wed Apr 4 05:07:38 PDT 2012

Hi tobi,

It looks like a trivial typo [1],  as you can find the comment of "Threshold":

  // Determine the current unrolling threshold.  While this is normally set
  // from UnrollThreshold, it is overridden to a smaller value if the current
  // function is marked as optimize-for-size, and the unroll threshold was
  // not user specified.
  unsigned Threshold = CurrentThreshold;
  if (!UserThreshold &&
    Threshold = OptSizeUnrollThreshold;

The "Threshold" is overridden by the the value of
"OptSizeUnrollThreshold" if the function requires to be optimized for
size. Hence, when we are reducing the unroll count of the loop to meet
the threshold constraint, the original code reduce the unroll count
according the variable "CurrentThreshold", instead of "Threshold",
which may be adjusted by the function attribute.

The original code:
      if (TripCount) {
        // Reduce unroll count to be modulo of TripCount for partial unrolling
        Count = CurrentThreshold / LoopSize;
<--------------------------should use Threshold
        while (Count != 0 && TripCount%Count != 0)

best regards


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