[PATCH] D95806: [LoopUnrollAndJam] Check if the loops have an Exit Block

[Sidharth Baveja via Phabricator via llvm-commits]

sidbav created this revision.
sidbav added reviewers: Whitney, bmahjour, etiotto, Meinersbur, dmgreen.
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This resolves an issue posted on Bugzilla. https://bugs.llvm.org/show_bug.cgi?id=48764

This issue took place because loops which did not have an exit block were allowed to unrolled and jam.

This patch ensures that loops which only have an exit block will be allowed to be unrolled and jammed.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D95806

Files:
  llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp


Index: llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
===================================================================
--- llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
+++ llvm/lib/Transforms/Utils/LoopUnrollAndJam.cpp
@@ -831,6 +831,13 @@
     if (SubLoopsSize != 1)
       return false;
 
+    // If the Loop does not have an exit block, cannot perform unroll and jam
+    if (!L->getExitBlock()) {
+      LLVM_DEBUG(dbgs() << "Won't unroll-and-jam; Loop does not have an exit "
+                           "block\n");
+      return false;
+    }
+
     L = L->getSubLoops()[0];
   } while (L);
 


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