Congzhe Cao 76be554931 [DependenceAnalysis][PR56275] Normalize negative dependence analysis results ...

This patch is the first of the two-patch series (D130188, D130179) that
resolve PR56275 (https://github.com/llvm/llvm-project/issues/56275)
which is a missed opportunity, where a perfrectly valid case for loop
interchange failed interchange legality.

If the distance/direction vector produced by dependence analysis (DA) is
negative, it needs to be normalized (reversed). This patch provides helper
functions `isDirectionNegative()` and `normalize()` in DA that does the
normalization, and clients can query DA to do normalization if needed.

A pass option `<normalized-results>` is added to DependenceAnalysisPrinterPass,
and we leverage it to update DA test cases to make sure of test coverage. The
test cases added in `Banerjee.ll` shows that negative vectors are normalized
with `print<da><normalized-results>`.

Reviewed By: bmahjour, Meinersbur, #loopoptwg

Differential Revision: https://reviews.llvm.org/D130188

2022-08-03 19:59:00 -04:00

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