[llvm] [VPlan] Insert VPBlendRecipes in post order. NFC (PR #201782)

[David Sherwood via llvm-commits]

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@@ -136,6 +138,10 @@ void VPPredicator::createBlockInMask(VPBasicBlock *VPBB) {
   // Start inserting after the block's phis, which be replaced by blends later.
   Builder.setInsertPoint(VPBB, VPBB->getFirstNonPhi());
 
+  // Keep track of where in VPBB we are inserting the masks into.
+  scope_exit UpdateInsertPoint(
+      [this, &VPBB]() { InsertPoints[VPBB] = Builder.getInsertPoint(); });
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david-arm wrote:

If there is only one mask per block, is it worth asserting that `InsertPoints[VPBB]` is null before writing to it?

https://github.com/llvm/llvm-project/pull/201782