[PATCH] D139403: [SCEV] Compute symbolic exit count for 'and' conditions

[Nikita Popov via Phabricator via llvm-commits]

nikic added inline comments.


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Comment at: llvm/lib/Analysis/ScalarEvolution.cpp:8715
+    if (EL.ExactNotTaken != getCouldNotCompute() ||
+        EL.SymbolicMaxNotTaken != getCouldNotCompute())
       ExitCounts.emplace_back(ExitBB, EL);
----------------
Why the new condition here?


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Comment at: llvm/test/Analysis/ScalarEvolution/widenable-condition.ll:27
 ; CHECK-NEXT:  Loop %loop: constant max backedge-taken count is 1999
-; CHECK-NEXT:  Loop %loop: Unpredictable symbolic max backedge-taken count.
+; CHECK-NEXT:  Loop %loop: symbolic max backedge-taken count is 1999
 ; CHECK-NEXT:  Loop %loop: Unpredictable predicated backedge-taken count.
----------------
I don't really get why this patch introduces these changes (i.e. why this wasn't the result previously). Aren't we already assigning the constant max to the symbol max if there is no exact?


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D139403/new/

https://reviews.llvm.org/D139403