[CGP] Use getAllOnesValue()

Split out from #80309.

Author: nikic

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -1643,7 +1643,7 @@ static bool matchUAddWithOverflowConstantEdgeCases(CmpInst *Cmp,
   if (Pred == ICmpInst::ICMP_EQ && match(B, m_AllOnes()))
     B = ConstantInt::get(B->getType(), 1);
   else if (Pred == ICmpInst::ICMP_NE && match(B, m_ZeroInt()))
-    B = ConstantInt::get(B->getType(), -1);
+    B = Constant::getAllOnesValue(B->getType());
   else
     return false;