[llvm] [loop-vectorize] Fix crash when using types that aren't known scale factors (PR #136680)

[Nicholas Guy via llvm-commits]

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@@ -1030,6 +1030,27 @@ for.body:                                         ; preds = %for.body.preheader,
   br i1 %exitcond.not, label %for.cond.cleanup, label %for.body, !loop !1
 }
 
+
+define i40 @chained_partial_reduce_not_known_factor(i32 %a, i32 %b, i32 %N) {
+entry:
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NickGuy-Arm wrote:

Added, I also noticed that, since removing the no-op `or`, this is no longer necessarily a chained partial reduction. So I've moved the test and added a comment to illustrate more clearly what the purpose of the test is.

https://github.com/llvm/llvm-project/pull/136680