[llvm] [ConstantRange] Expand makeAllowedICmpRegion to use samesign to give tighter range (PR #174355)

[Adar Dagan via llvm-commits]

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@@ -1056,6 +1056,19 @@ define i1 @neg_assume_trunc_eq_one(i8 %x) {
   ret i1 %q
 }
 
+define i8 @remove_for_samesign(i8 %x) {
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Adar-Dagan wrote:

Yes, I meant to show here that instcombine does an optimization that leads to loss of information in computeConstantRange without this patch. I'll remove it and add to the description instead

https://github.com/llvm/llvm-project/pull/174355