[llvm][NFC] Cleanup uses of std::function in Inlining-related APIs

Summary:
Replacing uses of std::function pointers or refs, or Optional, to
function_ref, since the usage pattern allows that. If the function is
optional, using a default parameter value (nullptr). This led to a few
parameter reshufles, to push all optionals to the end of the parameter
list.

Reviewers: davidxl, dblaikie

Subscribers: arsenm, jvesely, nhaehnle, eraman, hiraditya, haicheng, kerbowa, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D79917
diff --git a/llvm/lib/Analysis/InlineAdvisor.cpp b/llvm/lib/Analysis/InlineAdvisor.cpp
index 16ab759..dcaf9d0f 100644
--- a/llvm/lib/Analysis/InlineAdvisor.cpp
+++ b/llvm/lib/Analysis/InlineAdvisor.cpp
@@ -99,11 +99,7 @@
               *CB.getParent()->getParent()->getParent());
 
   auto &ORE = FAM.getResult<OptimizationRemarkEmitterAnalysis>(Caller);
-  // FIXME: make GetAssumptionCache's decl similar to the other 2 below. May
-  // need changing the type of getInlineCost parameters? Also see similar case
-  // in Inliner.cpp
-  std::function<AssumptionCache &(Function &)> GetAssumptionCache =
-      [&](Function &F) -> AssumptionCache & {
+  auto GetAssumptionCache = [&](Function &F) -> AssumptionCache & {
     return FAM.getResult<AssumptionAnalysis>(F);
   };
   auto GetBFI = [&](Function &F) -> BlockFrequencyInfo & {
@@ -119,8 +115,8 @@
     bool RemarksEnabled =
         Callee.getContext().getDiagHandlerPtr()->isMissedOptRemarkEnabled(
             DEBUG_TYPE);
-    return getInlineCost(CB, Params, CalleeTTI, GetAssumptionCache, {GetBFI},
-                         GetTLI, PSI, RemarksEnabled ? &ORE : nullptr);
+    return getInlineCost(CB, Params, CalleeTTI, GetAssumptionCache, GetTLI,
+                         GetBFI, PSI, RemarksEnabled ? &ORE : nullptr);
   };
   auto OIC = llvm::shouldInline(CB, GetInlineCost, ORE);
   return std::make_unique<DefaultInlineAdvice>(this, CB, OIC, ORE);