[llvm] [DependenceAnalysis] Extending SIV to handle separate loops (PR #128782)

[Michael Kruse via llvm-commits]

================
@@ -809,8 +897,29 @@ bool isLoadOrStore(const Instruction *I) {
 //     e - 5
 //     f - 6
 //     g - 7 = MaxLevels
+// If ConsiderSeparateLoops is true then we also want to consider similar
+// seperate loops. Assume that loop nests at level c and e are similar,
+// meaning that they have the same tripcount and depth. Then we consider
+// them as a separate common level.
+//     a      - 1
+//     b      - 2
+//     <c, e> - 3 = CommonLevels
+//     d      - 4 = SrcLevels
+//     f      - 5
+//     g      - 6 = MaxLevels
+// Initially similar separate levels are included in common levels. After
+// the separate level extraction at the end of the depends api we have
+//     a      - 1
+//     b      - 2 = CommonLevels
+//     <c, e> - 3 : A SeparateLevel
+//     d      - 4 = SrcLevels
+//     f      - 6
+//     g      - 7 = MaxLevels
----------------
Meinersbur wrote:

What happened with level 5?

There are lots of references to the loop numbering scheme other than SIV that don't account for the change, e.g. `getSplitIteration`. 

https://github.com/llvm/llvm-project/pull/128782