[CSSPGO] Add stats for pre-inliner

[wenlei]

Summary

Add some stats to help tuning pre-inliner.

[wlei]

LGTM, thanks!

llvm/tools/llvm-profgen/CSPreInliner.cpp

 //===-- CSPreInliner.cpp - Profile guided preinliner -------------- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "CSPreInliner.h"
 #include "ProfiledBinary.h"
 #include "llvm/ADT/SCCIterator.h"
+#include "llvm/ADT/Statistic.h"
 #include <cstdint>
 #include <queue>
 
 #define DEBUG_TYPE "cs-preinliner"
 
 using namespace llvm;
 using namespace sampleprof;
 
+STATISTIC(PreInlNumCSInlined,
+          "Number of functions inlined with context sensitive profile");
+STATISTIC(PreInlNumCSNotInlined,
+          "Number of functions not inlined with context sensitive profile");
+STATISTIC(PreInlNumCSInlinedHitMinLimit,
+          "Number of functions with FDO inline stopped due to min size limit");
+STATISTIC(PreInlNumCSInlinedHitMaxLimit,
+          "Number of functions with FDO inline stopped due to max size limit");
+STATISTIC(
+    PreInlNumCSInlinedHitGrowthLimit,
+    "Number of functions with FDO inline stopped due to growth size limit");
+
 // The switches specify inline thresholds used in SampleProfileLoader inlining.
 // TODO: the actual threshold to be tuned here because the size here is based
 // on machine code not LLVM IR.
 extern cl::opt<int> SampleHotCallSiteThreshold;
 extern cl::opt<int> SampleColdCallSiteThreshold;
 extern cl::opt<int> ProfileInlineGrowthLimit;
 extern cl::opt<int> ProfileInlineLimitMin;
 extern cl::opt<int> ProfileInlineLimitMax;
void CSPreInliner::processFunction(const StringRef Name) {
 
   while (!CQueue.empty() && FuncFinalSize < SizeLimit) {
     ProfiledInlineCandidate Candidate = CQueue.top();
     CQueue.pop();
     bool ShouldInline = false;
     if ((ShouldInline = shouldInline(Candidate))) {
       // We mark context as inlined as the corresponding context profile
       // won't be merged into that function's base profile.
+      ++PreInlNumCSInlined;
       ContextTracker.markContextSamplesInlined(Candidate.CalleeSamples);
       Candidate.CalleeSamples->getContext().setAttribute(
           ContextShouldBeInlined);
       FuncFinalSize += Candidate.SizeCost;
       getInlineCandidates(CQueue, Candidate.CalleeSamples);
+    } else {
+      ++PreInlNumCSNotInlined;
     }
     LLVM_DEBUG(dbgs() << (ShouldInline ? "  Inlined" : "  Outlined")
                       << " context profile for: "
                       << Candidate.CalleeSamples->getContext().toString()
                       << " (callee size: " << Candidate.SizeCost
                       << ", call count:" << Candidate.CallsiteCount << ")\n");
   }
 
+  if (!CQueue.empty()) {
+    if (SizeLimit == (unsigned)ProfileInlineLimitMax)
+      ++PreInlNumCSInlinedHitMaxLimit;
+    else if (SizeLimit == (unsigned)ProfileInlineLimitMin)
+      ++PreInlNumCSInlinedHitMinLimit;
+    else
+      ++PreInlNumCSInlinedHitGrowthLimit;
+  }
+
   LLVM_DEBUG({
     if (!CQueue.empty())
       dbgs() << "  Inline candidates ignored due to size limit (inliner "
                 "original size: "
              << FuncSize << ", inliner final size: " << FuncFinalSize
              << ", size limit: " << SizeLimit << ")\n";
 
     while (!CQueue.empty()) {