RFC: vectorizer cost model

Devang Patel devang.patel@gmail.com
Tue Feb 20 18:10:00 GMT 2007


>>  * How do we compare the costs of if-converted vectorized code to
>>    it's scalar counterpart?

o It may be convenient to calculate scalar cost during if-conversion itself.

o It is possible that size of two sibling blocks (Block_A & Block_B)
does not match at the beginning of tree-ssa level if conversion.
As a first step, to stay on conservative side, it makes sense
consider the scalar cost of smaller block while calculating scalar cost.
Note, smaller block may not exist.

   if (condition)
     Block_A
   else
     Block B

-
Devang



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