[llvm] [NFC][LoopVectorize] Add more simple early exit tests (PR #112529)

[David Sherwood via llvm-commits]

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@@ -918,6 +917,189 @@ loop.end:
 }
 
 
+define i64 @multiple_exiting_one_early_same_exit_phi_of_consts() {
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david-arm wrote:

Sure, that makes sense. If it's ok with you, I'll land this patch first then follow up with a simple refactor that collects tests of the same class in their own file, i.e. early exits with no outside users of loop variables, ones that use loop variables, tests with multiple early exits (countable + uncountable), tests for different memory access patterns, etc.

https://github.com/llvm/llvm-project/pull/112529