[llvm] [VPlan] Simplify branch on False in VPlan transform (NFC). (PR #140409)

[Florian Hahn via llvm-commits]

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@@ -526,56 +528,51 @@ void VPlanTransforms::prepareForVectorization(
   VPBasicBlock *ScalarPH = Plan.createVPBasicBlock("scalar.ph");
   VPBlockUtils::connectBlocks(ScalarPH, Plan.getScalarHeader());
 
-  // If needed, add a check in the middle block to see if we have completed
-  // all of the iterations in the first vector loop.  Three cases:
-  // 1) If we require a scalar epilogue, there is no conditional branch as
-  //    we unconditionally branch to the scalar preheader.  Remove the recipes
-  //    from the exit blocks.
-  // 2) If (N - N%VF) == N, then we *don't* need to run the remainder.
-  //    Thus if tail is to be folded, we know we don't need to run the
-  //    remainder and we can set the condition to true.
-  // 3) Otherwise, construct a runtime check.
-
-  if (!RequiresScalarEpilogueCheck) {
-    if (auto *LatchExitVPB = MiddleVPBB->getSingleSuccessor())
-      VPBlockUtils::disconnectBlocks(MiddleVPBB, LatchExitVPB);
-    VPBlockUtils::connectBlocks(MiddleVPBB, ScalarPH);
-    VPBlockUtils::connectBlocks(Plan.getEntry(), ScalarPH);
-    Plan.getEntry()->swapSuccessors();
-
-    // The exit blocks are unreachable, remove their recipes to make sure no
-    // users remain that may pessimize transforms.
-    for (auto *EB : Plan.getExitBlocks()) {
-      for (VPRecipeBase &R : make_early_inc_range(*EB))
-        R.eraseFromParent();
-    }
-    return;
-  }
-
-  // The connection order corresponds to the operands of the conditional branch,
-  // with the middle block already connected to the exit block.
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fhahn wrote:

Dropped by accident, restored, thanks

https://github.com/llvm/llvm-project/pull/140409