[llvm] [LoopVectorize] Add support for vectorisation of more early exit loops (PR #88385)

[Graham Hunter via llvm-commits]

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@@ -1439,6 +1496,103 @@ bool LoopVectorizationLegality::canVectorizeLoopNestCFG(
   return Result;
 }
 
+void LoopVectorizationLegality::recordExitingBlocks() {
+  SmallVector<BasicBlock *, 8> ExitingBlocks;
+  TheLoop->getExitingBlocks(ExitingBlocks);
+
+  SmallVector<BasicBlock *, 4> CountableExitingBBs;
+  PSE.getSE()->getCountableExitingBlocks(TheLoop, &CountableExitingBBs);
+
+  // There could be multiple exiting blocks with an exact exit-not-taken
+  // count. Find all of the uncountable early exit blocks, i.e. the ones with
+  // an unknown count.
+  SmallVector<BasicBlock *, 4> UncountableExitingBBs;
+  SmallVector<BasicBlock *, 4> UncountableExitBBs;
+  for (BasicBlock *BB1 : ExitingBlocks) {
+    if (!is_contained(CountableExitingBBs, BB1)) {
+      UncountableExitingBBs.push_back(BB1);
+
+      for (BasicBlock *BB2 : successors(BB1)) {
+        if (!TheLoop->contains(BB2)) {
+          UncountableExitBBs.push_back(BB2);
+          break;
+        }
+      }
+    }
+  }
+
+  CountableExitingBlocks = std::move(CountableExitingBBs);
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huntergr-arm wrote:

No need to create temporaries and move the data, you can just add directly to the member vectors in LVL.

https://github.com/llvm/llvm-project/pull/88385