[llvm] [ConstraintElimination] Extend unsigned-to-signed fact transfer (PR #66173)

[Antonio Frighetto via llvm-commits]

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@@ -748,13 +749,23 @@ void ConstraintInfo::transferToOtherSystem(
   default:
     break;
   case CmpInst::ICMP_ULT:
-    //  If B is a signed positive constant, A >=s 0 and A <s B.
+  case CmpInst::ICMP_ULE:
+    //  If B is a signed positive constant, A >=s 0 and A <s (or <=s) B.
     if (doesHold(CmpInst::ICMP_SGE, B, ConstantInt::get(B->getType(), 0))) {
       addFact(CmpInst::ICMP_SGE, A, ConstantInt::get(B->getType(), 0), NumIn,
               NumOut, DFSInStack);
-      addFact(CmpInst::ICMP_SLT, A, B, NumIn, NumOut, DFSInStack);
+      addFact(CmpInst::getSignedPredicate(Pred), A, B, NumIn, NumOut,
+              DFSInStack);
     }
     break;
+  case CmpInst::ICMP_UGE:
+  case CmpInst::ICMP_UGT:
+    //  If A and B are signed positive constants, A >s (or >=s) B.
+    if (doesHold(CmpInst::ICMP_SGE, B, ConstantInt::get(B->getType(), 0)) &&
+        doesHold(CmpInst::ICMP_SGE, A, ConstantInt::get(B->getType(), 0)))
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antoniofrighetto wrote:

I'm not really sure why I was constraining B as well. Indeed, if $A \geq_{u} B \land A \geq_{s} 0$ holds and, e.g., $A$ and $B$ are 8-bit integers, then $A$ is in $[0, 127]$, therefore $B >= 0$ must hold. Fixed, thanks.

https://github.com/llvm/llvm-project/pull/66173