[ValueTracking] Add fast path to avoid second recursive call in isKnownPositive; NFC

Just a simple compile time improvement. This function isn't used much,
however, so its not particularly impactful.

Closes llvm#83638

Author: goldsteinn

llvm/lib/Analysis/ValueTracking.cpp

@@ -294,9 +294,11 @@ bool llvm::isKnownPositive(const Value *V, const SimplifyQuery &SQ,
   if (auto *CI = dyn_cast<ConstantInt>(V))
     return CI->getValue().isStrictlyPositive();
 
-  // TODO: We'd doing two recursive queries here.  We should factor this such
-  // that only a single query is needed.
-  return isKnownNonNegative(V, SQ, Depth) && ::isKnownNonZero(V, Depth, SQ);
+  // If `isKnownNonNegative` ever becomes more sophisticated, make sure to keep
+  // this updated.
+  KnownBits Known = computeKnownBits(V, Depth, SQ);
+  return Known.isNonNegative() &&
+         (Known.isNonZero() || ::isKnownNonZero(V, Depth, SQ));
 }
 
 bool llvm::isKnownNegative(const Value *V, const SimplifyQuery &SQ,