[llvm] [VPlan] Add initial CFG simplification, removing BranchOnCond true. (PR #106748)

[Florian Hahn via llvm-commits]

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@@ -1437,6 +1437,49 @@ void VPlanTransforms::truncateToMinimalBitwidths(
          "some entries in MinBWs haven't been processed");
 }
 
+/// Remove BranchOnCond recipes with constant conditions together with removing
+/// dead edges to their successors.
+static void simplifyCFG(VPlan &Plan) {
+  using namespace llvm::VPlanPatternMatch;
+  for (VPBasicBlock *VPBB : VPBlockUtils::blocksOnly<VPBasicBlock>(
+           vp_depth_first_deep(Plan.getEntry()))) {
+    if (VPBB->getNumSuccessors() != 2 || VPBB->begin() == VPBB->end() ||
+        !match(&VPBB->back(), m_BranchOnCond(m_True())))
+      continue;
+
+    VPBasicBlock *DeadSucc = cast<VPBasicBlock>(VPBB->getSuccessors()[1]);
+    const auto &Preds = DeadSucc->getPredecessors();
+    unsigned DeadIdx = std::distance(Preds.begin(), find(Preds, VPBB));
+
+    // Remove values coming from VPBB from phi-like recipes in DeadSucc.
+    for (VPRecipeBase &R : make_early_inc_range(*DeadSucc)) {
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fhahn wrote:

Done, thanks

https://github.com/llvm/llvm-project/pull/106748