[llvm] [LoopIdiomVectorize] Remove redundant DomTreeUpdates (PR #94681)

[David Sherwood via llvm-commits]

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@@ -679,7 +657,12 @@ void LoopIdiomVectorize::transformByteCompare(GetElementPtrInst *GEPA,
   BasicBlock *Header = CurLoop->getHeader();
   BranchInst *PHBranch = cast<BranchInst>(Preheader->getTerminator());
   IRBuilder<> Builder(PHBranch);
+
+  // Safeguard to check if we build the correct DomTree with DTU.
+  auto CheckDTU = llvm::make_scope_exit(
+      [this]() { assert(DT->verify() && "Ill-formed DomTree built by DTU"); });
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david-arm wrote:

OK thanks for explaining. Perhaps it's just me that didn't find this obvious, but I wonder if it would be useful to leave a brief comment explaining how this works? For example,

```
  // Safeguard to check if we build the correct DomTree with DTU. In accordance
  // with C++ rules, destructors are called in reverse order so the verify()
  // occurs after ~DTU.
```

https://github.com/llvm/llvm-project/pull/94681