[llvm] [LoopFusion] Extending SIV to handle separate loops (PR #146383)

[via llvm-commits]

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@@ -1371,6 +1373,33 @@ struct LoopFuser {
                           << "\n");
       }
 #endif
+      unsigned Levels = DepResult->getLevels();
+      unsigned SameSDLevels = DepResult->getSameSDLevels();
+      unsigned CurLoopLevel = FC0.L->getLoopDepth();
+
+      bool OuterEqDir = true;
+      for (unsigned II = 1; II <= std::min(CurLoopLevel - 1, Levels); ++II) {
+        unsigned Direction = DepResult->getDirection(II, II > Levels);
+        if (!(Direction & Dependence::DVEntry::EQ)) {
+          // Different accesses in the outer levels of CurLoopLevel
+          OuterEqDir = false;
+          break;
+        }
+      }
+      if (!OuterEqDir || CurLoopLevel > Levels + SameSDLevels) {
+        LLVM_DEBUG(dbgs() << "Safe to fuse with no dependency\n");
+        NumDepSafeFused++;
+        return true;
+      }
+
+      assert(CurLoopLevel > Levels && "Fusion candidates are not separated");
+      unsigned CurDir = DepResult->getDirection(CurLoopLevel, true);
+      if (!(CurDir & Dependence::DVEntry::GT)) {
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CongzheUalberta wrote:

Would it be more readable if it is changed to the following?
```if (CurDir != Dependence::DVEntry::GT)```



https://github.com/llvm/llvm-project/pull/146383