[llvm] [DA] Set Distance to zero when Direction is EQ (PR #147966)

[Michael Kruse via llvm-commits]

================
@@ -187,6 +187,18 @@ static void dumpExampleDependence(raw_ostream &OS, DependenceInfo *DA,
           OS << "  da analyze - ";
           if (auto D = DA->depends(&*SrcI, &*DstI,
                                    /*UnderRuntimeAssumptions=*/true)) {
+
+            // Verify that the distance begin zero is equivalent to the
+            // direction being EQ.
+            for (unsigned Level = 1; Level <= D->getLevels(); Level++) {
+              const SCEV *Distance = D->getDistance(Level);
+              bool IsDistanceZero = Distance && Distance->isZero();
+              bool IsDirectionEQ =
+                  D->getDirection(Level) == Dependence::DVEntry::EQ;
+              assert(IsDistanceZero == IsDirectionEQ &&
+                     "Inconsistent distance and direction.");
+            }
----------------
Meinersbur wrote:

This will give unused variable warnings in non-assert builds. So only compile this in assert builds:
```suggestion
#ifndef NDEBUG
            // Verify that the distance begin zero is equivalent to the
            // direction being EQ.
            for (unsigned Level = 1; Level <= D->getLevels(); Level++) {
              const SCEV *Distance = D->getDistance(Level);
              bool IsDistanceZero = Distance && Distance->isZero();
              bool IsDirectionEQ =
                  D->getDirection(Level) == Dependence::DVEntry::EQ;
              assert(IsDistanceZero == IsDirectionEQ &&
                     "Inconsistent distance and direction.");
            }
#endif
```

https://github.com/llvm/llvm-project/pull/147966