[llvm] [CodeGen][StaticDataPartitioning]Place local-linkage global variables in hot or unlikely prefixed sections based on profile information (PR #125756)

[Snehasish Kumar via llvm-commits]

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@@ -0,0 +1,65 @@
+#include "llvm/Analysis/StaticDataProfileInfo.h"
+#include "llvm/Analysis/ProfileSummaryInfo.h"
+#include "llvm/IR/Constant.h"
+#include "llvm/IR/GlobalVariable.h"
+#include "llvm/InitializePasses.h"
+#include "llvm/ProfileData/InstrProf.h"
+#include <sys/types.h>
+
+using namespace llvm;
+void StaticDataProfileInfo::addConstantProfileCount(
+    const Constant *C, std::optional<uint64_t> Count) {
+  if (!Count) {
+    ConstantWithoutCounts.insert(C);
+    return;
+  }
+  uint64_t &OriginalCount = ConstantProfileCounts[C];
+  OriginalCount = llvm::SaturatingAdd(*Count, OriginalCount);
+  // Clamp the count to getInstrMaxCountValue. InstrFDO reserves a few
+  // large values for special use.
+  if (OriginalCount > getInstrMaxCountValue())
+    OriginalCount = getInstrMaxCountValue();
+}
+
+std::optional<uint64_t>
+StaticDataProfileInfo::getConstantProfileCount(const Constant *C) const {
+  auto I = ConstantProfileCounts.find(C);
+  if (I == ConstantProfileCounts.end())
+    return std::nullopt;
+  return I->second;
+}
+
+StringRef StaticDataProfileInfo::getConstantSectionPrefix(
+    const Constant *C, const ProfileSummaryInfo *PSI) const {
+  auto Count = getConstantProfileCount(C);
+  if (!Count)
+    return "";
+  if (PSI->isHotCount(*Count))
+    return "hot";
+  if (ConstantWithoutCounts.count(C))
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snehasish wrote:

Should we check this before getConstantProfileCount? Is there a reasoning for the current ordering of checks?

https://github.com/llvm/llvm-project/pull/125756