[profdata] Use --hot-func-list to show all hot functions (#149428)

The `--hot-func-list` flag is used for sample profiles to dump the list
of hot functions. Add support to dump hot functions for IRPGO profiles
as well.

This also removes a `priority_queue` used for `--topn`. We can instead
store all functions and sort at the end before dumping. Since we are
storing `StringRef`s, I believe this won't consume too much memory.

Author: ellishg

llvm/test/tools/llvm-profdata/c-general.test

@@ -22,6 +22,6 @@ SWITCHES-LABEL: Functions shown: 1
 CHECK-LABEL: Total functions: 12
 CHECK-NEXT: Maximum function count: 1
 CHECK-NEXT: Maximum internal block count: 100
-TOPN: boolean_operators, max count = 100
-TOPN-NEXT: simple_loops, max count = 100
-TOPN-NEXT:  conditionals, max count = 100
+TOPN:         simple_loops, max count = 100
+TOPN-NEXT:    conditionals, max count = 100
+TOPN-NEXT:    boolean_operators, max count = 100

llvm/test/tools/llvm-profdata/show-hot.proftext

@@ -0,0 +1,35 @@
+# RUN: llvm-profdata show %s --hot-func-list | FileCheck %s
+
+# CHECK: # Hot count threshold: 101
+# CHECK: hot_b
+# CHECK: hot_a
+# CHECK: hot_c
+
+:ir
+hot_a
+# Func Hash:
+0x1234
+# Num Counters:
+1
+# Counter Values:
+101
+
+hot_b
+0x5678
+1
+202
+
+hot_c
+0x5678
+1
+101
+
+cold_d
+0xabcd
+1
+1
+
+cold_e
+0xefff
+1
+0

llvm/tools/llvm-profdata/llvm-profdata.cpp

@@ -46,7 +46,6 @@
 #include <algorithm>
 #include <cmath>
 #include <optional>
-#include <queue>
 
 using namespace llvm;
 using ProfCorrelatorKind = InstrProfCorrelator::ProfCorrelatorKind;
@@ -2846,9 +2845,8 @@ static int showInstrProfile(ShowFormat SFormat, raw_fd_ostream &OS) {
   auto FS = vfs::getRealFileSystem();
   auto ReaderOrErr = InstrProfReader::create(Filename, *FS);
   std::vector<uint32_t> Cutoffs = std::move(DetailedSummaryCutoffs);
-  if (ShowDetailedSummary && Cutoffs.empty()) {
+  if (Cutoffs.empty() && (ShowDetailedSummary || ShowHotFuncList))
     Cutoffs = ProfileSummaryBuilder::DefaultCutoffs;
-  }
   InstrProfSummaryBuilder Builder(std::move(Cutoffs));
   if (Error E = ReaderOrErr.takeError())
     exitWithError(std::move(E), Filename);
@@ -2860,15 +2858,7 @@ static int showInstrProfile(ShowFormat SFormat, raw_fd_ostream &OS) {
   int NumVPKind = IPVK_Last - IPVK_First + 1;
   std::vector<ValueSitesStats> VPStats(NumVPKind);
 
-  auto MinCmp = [](const std::pair<std::string, uint64_t> &v1,
-                   const std::pair<std::string, uint64_t> &v2) {
-    return v1.second > v2.second;
-  };
-
-  std::priority_queue<std::pair<std::string, uint64_t>,
-                      std::vector<std::pair<std::string, uint64_t>>,
-                      decltype(MinCmp)>
-      HottestFuncs(MinCmp);
+  std::vector<std::pair<StringRef, uint64_t>> NameAndMaxCount;
 
   if (!TextFormat && OnlyListBelow) {
     OS << "The list of functions with the maximum counter less than "
@@ -2942,15 +2932,8 @@ static int showInstrProfile(ShowFormat SFormat, raw_fd_ostream &OS) {
     if (OnlyListBelow)
       continue;
 
-    if (TopNFunctions) {
-      if (HottestFuncs.size() == TopNFunctions) {
-        if (HottestFuncs.top().second < FuncMax) {
-          HottestFuncs.pop();
-          HottestFuncs.emplace(std::make_pair(std::string(Func.Name), FuncMax));
-        }
-      } else
-        HottestFuncs.emplace(std::make_pair(std::string(Func.Name), FuncMax));
-    }
+    if (TopNFunctions || ShowHotFuncList)
+      NameAndMaxCount.emplace_back(Func.Name, FuncMax);
 
     if (Show) {
       if (!ShownFunctions)
@@ -3029,16 +3012,27 @@ static int showInstrProfile(ShowFormat SFormat, raw_fd_ostream &OS) {
        << "): " << PS->getNumFunctions() - BelowCutoffFunctions << "\n";
   }
 
+  // Sort by MaxCount in decreasing order
+  llvm::stable_sort(NameAndMaxCount, [](const auto &L, const auto &R) {
+    return L.second > R.second;
+  });
   if (TopNFunctions) {
-    std::vector<std::pair<std::string, uint64_t>> SortedHottestFuncs;
-    while (!HottestFuncs.empty()) {
-      SortedHottestFuncs.emplace_back(HottestFuncs.top());
-      HottestFuncs.pop();
-    }
     OS << "Top " << TopNFunctions
        << " functions with the largest internal block counts: \n";
-    for (auto &hotfunc : llvm::reverse(SortedHottestFuncs))
-      OS << "  " << hotfunc.first << ", max count = " << hotfunc.second << "\n";
+    auto TopFuncs = ArrayRef(NameAndMaxCount).take_front(TopNFunctions);
+    for (auto [Name, MaxCount] : TopFuncs)
+      OS << "  " << Name << ", max count = " << MaxCount << "\n";
+  }
+
+  if (ShowHotFuncList) {
+    auto HotCountThreshold =
+        ProfileSummaryBuilder::getHotCountThreshold(PS->getDetailedSummary());
+    OS << "# Hot count threshold: " << HotCountThreshold << "\n";
+    for (auto [Name, MaxCount] : NameAndMaxCount) {
+      if (MaxCount < HotCountThreshold)
+        break;
+      OS << Name << "\n";
+    }
   }
 
   if (ShownFunctions && ShowIndirectCallTargets) {