[llvm] LoopVectorize: run verifyFunction once (PR #91470)

[Florian Hahn via llvm-commits]

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@@ -10359,6 +10357,8 @@ LoopVectorizeResult LoopVectorizePass::runImpl(
     }
   }
 
+  assert(!Changed || !verifyFunction(F, &dbgs()));
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fhahn wrote:

`Changed` may also be set if the loop only has been modified by `simplifyLoop` or `formLCSSARecursively`, so we will verify in cases where we didn't before?

https://github.com/llvm/llvm-project/pull/91470