[llvm] Reland "[BasicBlockUtils] Fix dominator tree update for entry block in splitBlockBefore() (#178895) (PR #179392)

[Mingjie Xu via llvm-commits]

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@@ -691,7 +691,7 @@ bool CodeGenPrepare::_run(Function &F) {
     MadeChange |= optimizePhiTypes(F);
 
     if (MadeChange)
-      eliminateFallThrough(F, DT.get());
+      eliminateFallThrough(F, &getDT(F));
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Enna1 wrote:

Thanks, this makes sense.
keep `DT.get()` here.

https://github.com/llvm/llvm-project/pull/179392