[llvm] [VPlan] Introduce child regions as VPlan transform. (PR #129402)

[Florian Hahn via llvm-commits]

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@@ -423,21 +338,11 @@ void PlainCFGBuilder::buildPlainCFG(
     BasicBlock *IRSucc1 = BI->getSuccessor(1);
     VPBasicBlock *Successor0 = getOrCreateVPBB(IRSucc0);
     VPBasicBlock *Successor1 = getOrCreateVPBB(IRSucc1);
-    if (BB == LoopForBB->getLoopLatch()) {
-      // For a latch we need to set the successor of the region rather than that
-      // of VPBB and it should be set to the exit, i.e., non-header successor,
-      // except for the top region, which is handled elsewhere.
-      assert(LoopForBB != TheLoop &&
-             "Latch of the top region should have been handled earlier");
-      Region->setOneSuccessor(isHeaderVPBB(Successor0) ? Successor1
-                                                       : Successor0);
-      Region->setExiting(VPBB);
-      continue;
-    }
 
-    // Don't connect any blocks outside the current loop except the latch for
-    // now. The latch is handled above.
-    if (LoopForBB) {
+    // Don't connect any blocks outside the current loop except the latches for
+    // inner loops.
+    if (LoopForBB &&
+        (LoopForBB == TheLoop || BB != LoopForBB->getLoopLatch())) {
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fhahn wrote:

> This is somewhat confusing: can LoopForBB be null, given that BB traverses all (and only) blocks of TheLoop?

It cannot be null, I removed the check.

Initial VPlan-construction should also include connecting the exit blocks of the top-level loop eventually. I have a follow-up patch to do so, as it is probably best tackled separately.



https://github.com/llvm/llvm-project/pull/129402