[mlir][inliner] Return early if the inliningThreshold is 0U or -1U.

Computing the inlinling profitability can be costly due to walking the
graph when counting the number of operations.

This PR addresses that by returning early if the threshold is set to
never or always inline.

Author: naibaf7

mlir/lib/Transforms/InlinerPass.cpp

@@ -93,12 +93,17 @@ InlinerPass::InlinerPass(std::function<void(OpPassManager &)> defaultPipeline,
 // Return true if the inlining ratio does not exceed the threshold.
 static bool isProfitableToInline(const Inliner::ResolvedCall &resolvedCall,
                                  unsigned inliningThreshold) {
+  if (inliningThreshold == 0U)
+    return false;
+  if (inliningThreshold == -1U)
+    return true;
+
   Region *callerRegion = resolvedCall.sourceNode->getCallableRegion();
   Region *calleeRegion = resolvedCall.targetNode->getCallableRegion();
 
   // We should not get external nodes here, but just return true
   // for now to preserve the original behavior of the inliner pass.
-  if (!calleeRegion || !calleeRegion)
+  if (!callerRegion || !calleeRegion)
     return true;
 
   auto countOps = [](Region *region) {