[llvm] [LoopVectorize] Enable vectorisation of early exit loops with live-outs (PR #120567)

David Sherwood via llvm-commits llvm-commits at lists.llvm.org
Mon Jan 13 05:47:15 PST 2025


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@@ -501,7 +501,15 @@ void VPBasicBlock::execute(VPTransformState *State) {
     UnreachableInst *Terminator = State->Builder.CreateUnreachable();
     // Register NewBB in its loop. In innermost loops its the same for all
     // BB's.
-    if (State->CurrentParentLoop)
+    if (this == State->Plan->getEarlyExit()) {
+      // If this is the vector early exit block then it has a single successor,
+      // which is the uncountable early exit block of the original loop. The
+      // parent loop for the exit block may not be the same as the parent loop
+      // of the vectorised loop, so we have to treat this differently.
+      Loop *EEL = State->LI->getLoopFor(State->CFG.UncountableEarlyExitBB);
+      if (EEL)
+        EEL->addBasicBlockToLoop(NewBB, *State->LI);
+    } else if (State->CurrentParentLoop)
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david-arm wrote:

We can do it that way I think, but I guess that requires walking through the list returned by `getExitBlocks()` every time this function is called. I imagine that's quite a bit of compile time cost, but I suppose I can limit this to when `State->CFG.UncountableEarlyExitB` is non-null if that's ok?

https://github.com/llvm/llvm-project/pull/120567


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