[llvm] [SCEV] Add PHI SCEV verification to ensure availability at loop entry (PR #127550)

[via llvm-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-llvm-analysis

Author: Aleksandr Popov (aleks-tmb)

<details>
<summary>Changes</summary>



---
Full diff: https://github.com/llvm/llvm-project/pull/127550.diff


1 Files Affected:

- (modified) llvm/lib/Analysis/ScalarEvolution.cpp (+10) 


``````````diff
diff --git a/llvm/lib/Analysis/ScalarEvolution.cpp b/llvm/lib/Analysis/ScalarEvolution.cpp
index 8f74c1c398ced..2d1a57a72721d 100644
--- a/llvm/lib/Analysis/ScalarEvolution.cpp
+++ b/llvm/lib/Analysis/ScalarEvolution.cpp
@@ -14482,6 +14482,16 @@ void ScalarEvolution::verify() const {
                << "Delta: " << *Delta << "\n";
         std::abort();
       }
+
+      if (isa<PHINode>(I))
+        for (const Loop *L : ValidLoops)
+          if (SE.isAvailableAtLoopEntry(OldSCEV, L) !=
+              SE2.isAvailableAtLoopEntry(NewSCEV, L)) {
+            dbgs() << "Incorrect SCEV availability at loop entry\n"
+                   << "Old: " << *OldSCEV << "\n"
+                   << "New: " << *NewSCEV << "\n";
+            std::abort();
+          }
     }
   }
 

``````````

</details>


https://github.com/llvm/llvm-project/pull/127550