[llvm] [LoopIdiomVectorize] Test all needles when vectorising find_first_of loops. (PR #179298)

[David Sherwood via llvm-commits]

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@@ -1364,14 +1368,17 @@ Value *LoopIdiomVectorize::expandFindFirstByte(
   Search->addIncoming(SearchStart, BB0);
   Search->addIncoming(NextSearch, BB5);
   Needle->addIncoming(NeedleStart, BB1);
-  Needle->addIncoming(NextNeedle, BB4);
+  Needle->addIncoming(NextNeedle, BB2);
+  Match->addIncoming(MatchInit, BB1);
+  Match->addIncoming(MatchAcc, BB2);
   // These are needed to retain LCSSA form.
-  MatchLCSSA->addIncoming(Search, BB2);
-  MatchPredLCSSA->addIncoming(MatchPred, BB2);
+  MatchPred->addIncoming(MatchAcc, BB2);
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david-arm wrote:

nit: This is also a LCSSA variable so probably good to add LCSSA at the end to maintain the same convention. However, you already have a `MatchPredLCSSA` below, so perhaps rename to something like `MatchPredAccLCSSA`?

https://github.com/llvm/llvm-project/pull/179298