[llvm] [LV][NFC] Emit remarks when failing to vectorise early exit loops (PR #225078)

[David Sherwood via llvm-commits]

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@@ -3296,8 +3344,12 @@ static bool handleUncountableExitsWithSideEffects(
   auto Phis = ScalarPH->phis();
   // TODO: Handle more than one Phi; re-derive from IV.
   // TODO: Handle reductions.
-  if (range_size(Phis) != 1)
+  if (range_size(Phis) != 1) {
+    reportVectorizationFailure("Early exit loop with side effects contains "
+                               "unsupported reductions or recurrences.\n",
+                               "EarlyExitEffectsSideReductions", ORE, TheLoop);
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david-arm wrote:

Yeah, I just wanted to avoid overly verbose names as these tags aren't really useful to the end user. The alternative would be "EarlyExitSideEffectsInductionsReductionsOrRecurrences"

https://github.com/llvm/llvm-project/pull/225078