[Inlining] Make shouldBeDeferred static (NFC)

[kazu]

Summary

This patch makes shouldBeDeferred static because it is called only
from shouldInline in the same .cpp file.

[mtrofin]

lgtm, thanks!

llvm/include/llvm/Analysis/InlineAdvisor.h

 class BasicBlock;
 class CallBase;
 class Function;
 class OptimizationRemarkEmitter;
 
 // Default (manual policy) decision making helper APIs. Shared with the legacy
 // pass manager inliner.
 
-/// Return true if inlining of CB can block the caller from being
-/// inlined which is proved to be more beneficial. \p IC is the
-/// estimated inline cost associated with callsite \p CB.
-/// \p TotalSecondaryCost will be set to the estimated cost of inlining the
-/// caller if \p CB is suppressed for inlining.
-bool shouldBeDeferred(Function *Caller, InlineCost IC, int &TotalSecondaryCost,
-                      function_ref<InlineCost(CallBase &CB)> GetInlineCost);
-
 /// Return the cost only if the inliner should attempt to inline at the given
 /// CallSite. If we return the cost, we will emit an optimisation remark later
 /// using that cost, so we won't do so from this function. Return None if
 /// inlining should not be attempted.
 Optional<InlineCost>
 shouldInline(CallBase &CB, function_ref<InlineCost(CallBase &CB)> GetInlineCost,
              OptimizationRemarkEmitter &ORE);
 

llvm/lib/Analysis/InlineAdvisor.cpp

InlineDeferralScale("inline-deferral-scale",
                         cl::desc("Scale to limit the cost of inline deferral"),
                         cl::init(-1), cl::Hidden);
 
 /// Return true if inlining of CB can block the caller from being
 /// inlined which is proved to be more beneficial. \p IC is the
 /// estimated inline cost associated with callsite \p CB.
 /// \p TotalSecondaryCost will be set to the estimated cost of inlining the
 /// caller if \p CB is suppressed for inlining.
-bool llvm::shouldBeDeferred(
-    Function *Caller, InlineCost IC, int &TotalSecondaryCost,
+static bool
+shouldBeDeferred(Function *Caller, InlineCost IC, int &TotalSecondaryCost,
                  function_ref<InlineCost(CallBase &CB)> GetInlineCost) {
   // For now we only handle local or inline functions.
   if (!Caller->hasLocalLinkage() && !Caller->hasLinkOnceODRLinkage())
     return false;
   // If the cost of inlining CB is non-positive, it is not going to prevent the
   // caller from being inlined into its callers and hence we don't need to
   // defer.
   if (IC.getCost() <= 0)
     return false;