[llvm] [ConstraintElim] Bound non-increasing header IVs by start value. (PR #217921)

[Florian Hahn via llvm-commits]

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@@ -1134,9 +1158,10 @@ void State::addInfoForInductions(BasicBlock &BB) {
     WorkList.push_back(FactOrCheck::getConditionFact(
         DTN, CmpInst::ICMP_UGE, StartValue, PN,
         ConditionTy(CmpInst::ICMP_ULE, B, StartValue)));
-    WorkList.push_back(FactOrCheck::getConditionFact(
-        DTN, CmpInst::ICMP_SGE, StartValue, PN,
-        ConditionTy(CmpInst::ICMP_SLE, B, StartValue)));
+    if (!(Info.Decreasing && Info.Signed))
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fhahn wrote:

This should avoid adding the same fact again, as it should already be added without precondition in `addBoundsForHeaderInductions`.

The case where we needed to add with precondition was missing; I added 2 more tests.

https://github.com/llvm/llvm-project/pull/217921