[IR][AsmPrinter][ELF]Allow setting section prefix for and use the prefix when emitting global objects

llvm/include/llvm/IR/Function.h

@@ -334,12 +334,6 @@ class LLVM_ABI Function : public GlobalObject, public ilist_node<Function> {
   /// sample PGO, to enable the same inlines as the profiled optimized binary.
   DenseSet<GlobalValue::GUID> getImportGUIDs() const;
 
-  /// Set the section prefix for this function.
-  void setSectionPrefix(StringRef Prefix);
-
-  /// Get the section prefix for this function.
-  std::optional<StringRef> getSectionPrefix() const;
-
   /// hasGC/getGC/setGC/clearGC - The name of the garbage collection algorithm
   ///                             to use during code generation.
   bool hasGC() const {

llvm/include/llvm/IR/GlobalObject.h

@@ -124,6 +124,12 @@ class GlobalObject : public GlobalValue {
   /// appropriate default object file section.
   void setSection(StringRef S);
 
+  /// Set the section prefix for this global object.
+  void setSectionPrefix(StringRef Prefix);
+
+  /// Get the section prefix for this global object.
+  std::optional<StringRef> getSectionPrefix() const;
+
   bool hasComdat() const { return getComdat() != nullptr; }
   const Comdat *getComdat() const { return ObjComdat; }
   Comdat *getComdat() { return ObjComdat; }

llvm/include/llvm/IR/MDBuilder.h

@@ -89,8 +89,8 @@ class MDBuilder {
   MDNode *createFunctionEntryCount(uint64_t Count, bool Synthetic,
                                    const DenseSet<GlobalValue::GUID> *Imports);
 
-  /// Return metadata containing the section prefix for a function.
-  MDNode *createFunctionSectionPrefix(StringRef Prefix);
+  /// Return metadata containing the section prefix for a global object.
+  MDNode *createGlobalObjectSectionPrefix(StringRef Prefix);
 
   /// Return metadata containing the pseudo probe descriptor for a function.
   MDNode *createPseudoProbeDesc(uint64_t GUID, uint64_t Hash, StringRef FName);

llvm/lib/CodeGen/StaticDataSplitter.cpp

@@ -41,25 +41,17 @@ STATISTIC(NumUnknownJumpTables,
           "Number of jump tables with unknown hotness. Option "
           "-static-data-default-hotness specifies the hotness.");
 
-static cl::opt<MachineFunctionDataHotness> StaticDataDefaultHotness(
-    "static-data-default-hotness", cl::Hidden,
-    cl::desc("This option specifies the hotness of static data when profile "
-             "information is unavailable"),
-    cl::init(MachineFunctionDataHotness::Hot),
-    cl::values(clEnumValN(MachineFunctionDataHotness::Hot, "hot", "Hot"),
-               clEnumValN(MachineFunctionDataHotness::Cold, "cold", "Cold")));
-
 class StaticDataSplitter : public MachineFunctionPass {
   const MachineBranchProbabilityInfo *MBPI = nullptr;
   const MachineBlockFrequencyInfo *MBFI = nullptr;
   const ProfileSummaryInfo *PSI = nullptr;
 
-  // Returns true iff any jump table is hot-cold categorized.
-  bool splitJumpTables(MachineFunction &MF);
+  void updateStats(bool ProfileAvailable, const MachineJumpTableInfo *MJTI);
+  void updateJumpTableStats(bool ProfileAvailable,
+                            const MachineJumpTableInfo &MJTI);
 
-  // Same as above but works on functions with profile information.
-  bool splitJumpTablesWithProfiles(const MachineFunction &MF,
-                                   MachineJumpTableInfo &MJTI);
+  // Use profiles to partition static data.
+  bool partitionStaticDataWithProfiles(MachineFunction &MF);
 
 public:
   static char ID;
@@ -85,13 +77,22 @@ bool StaticDataSplitter::runOnMachineFunction(MachineFunction &MF) {
   MBFI = &getAnalysis<MachineBlockFrequencyInfoWrapperPass>().getMBFI();
   PSI = &getAnalysis<ProfileSummaryInfoWrapperPass>().getPSI();
 
-  return splitJumpTables(MF);
+  const bool ProfileAvailable = PSI && PSI->hasProfileSummary() && MBFI &&
+                                MF.getFunction().hasProfileData();
+  bool Changed = false;
+
+  if (ProfileAvailable)
+    Changed |= partitionStaticDataWithProfiles(MF);
+
+  updateStats(ProfileAvailable, MF.getJumpTableInfo());
+  return Changed;
 }
 
-bool StaticDataSplitter::splitJumpTablesWithProfiles(
-    const MachineFunction &MF, MachineJumpTableInfo &MJTI) {
+bool StaticDataSplitter::partitionStaticDataWithProfiles(MachineFunction &MF) {
   int NumChangedJumpTables = 0;
 
+  MachineJumpTableInfo *MJTI = MF.getJumpTableInfo();
+
   // Jump table could be used by either terminating instructions or
   // non-terminating ones, so we walk all instructions and use
   // `MachineOperand::isJTI()` to identify jump table operands.
@@ -100,70 +101,58 @@ bool StaticDataSplitter::splitJumpTablesWithProfiles(
   for (const auto &MBB : MF) {
     for (const MachineInstr &I : MBB) {
       for (const MachineOperand &Op : I.operands()) {
-        if (!Op.isJTI())
-          continue;
-        const int JTI = Op.getIndex();
-        // This is not a source block of jump table.
-        if (JTI == -1)
-          continue;
-
-        auto Hotness = MachineFunctionDataHotness::Hot;
-
-        // Hotness is based on source basic block hotness.
-        // TODO: PSI APIs are about instruction hotness. Introduce API for data
-        // access hotness.
-        if (PSI->isColdBlock(&MBB, MBFI))
-          Hotness = MachineFunctionDataHotness::Cold;
-
-        if (MJTI.updateJumpTableEntryHotness(JTI, Hotness))
-          ++NumChangedJumpTables;
+        if (Op.isJTI()) {
+          assert(MJTI != nullptr && "Jump table info is not available.");
+          const int JTI = Op.getIndex();
+          // This is not a source block of jump table.
+          if (JTI == -1)
+            continue;
+
+          auto Hotness = MachineFunctionDataHotness::Hot;
+
+          // Hotness is based on source basic block hotness.
+          // TODO: PSI APIs are about instruction hotness. Introduce API for
+          // data access hotness.
+          if (PSI->isColdBlock(&MBB, MBFI))
+            Hotness = MachineFunctionDataHotness::Cold;
+
+          if (MJTI->updateJumpTableEntryHotness(JTI, Hotness))
+            ++NumChangedJumpTables;
+        }
       }
     }
   }
   return NumChangedJumpTables > 0;
 }
 
-bool StaticDataSplitter::splitJumpTables(MachineFunction &MF) {
-  MachineJumpTableInfo *MJTI = MF.getJumpTableInfo();
-  if (!MJTI || MJTI->getJumpTables().empty())
-    return false;
+void StaticDataSplitter::updateJumpTableStats(
+    bool ProfileAvailable, const MachineJumpTableInfo &MJTI) {
 
-  const bool ProfileAvailable = PSI && PSI->hasProfileSummary() && MBFI &&
-                                MF.getFunction().hasProfileData();
-  auto statOnExit = llvm::make_scope_exit([&] {
-    if (!AreStatisticsEnabled())
-      return;
-
-    if (!ProfileAvailable) {
-      NumUnknownJumpTables += MJTI->getJumpTables().size();
-      return;
-    }
+  if (!ProfileAvailable) {
+    NumUnknownJumpTables += MJTI.getJumpTables().size();
+    return;
+  }
 
-    for (size_t JTI = 0; JTI < MJTI->getJumpTables().size(); JTI++) {
-      auto Hotness = MJTI->getJumpTables()[JTI].Hotness;
-      if (Hotness == MachineFunctionDataHotness::Hot) {
-        ++NumHotJumpTables;
-      } else {
-        assert(Hotness == MachineFunctionDataHotness::Cold &&
-               "A jump table is either hot or cold when profile information is "
-               "available.");
-        ++NumColdJumpTables;
-      }
+  for (size_t JTI = 0; JTI < MJTI.getJumpTables().size(); JTI++) {
+    auto Hotness = MJTI.getJumpTables()[JTI].Hotness;
+    if (Hotness == MachineFunctionDataHotness::Hot) {
+      ++NumHotJumpTables;
+    } else {
+      assert(Hotness == MachineFunctionDataHotness::Cold &&
+             "A jump table is either hot or cold when profile information is "
+             "available.");
+      ++NumColdJumpTables;
     }
-  });
-
-  // Place jump tables according to block hotness if function has profile data.
-  if (ProfileAvailable)
-    return splitJumpTablesWithProfiles(MF, *MJTI);
+  }
+}
 
-  // If function profile is unavailable (e.g., module not instrumented, or new
-  // code paths lacking samples), -static-data-default-hotness specifies the
-  // hotness.
-  for (size_t JTI = 0; JTI < MJTI->getJumpTables().size(); JTI++)
-    MF.getJumpTableInfo()->updateJumpTableEntryHotness(
-        JTI, StaticDataDefaultHotness);
+void StaticDataSplitter::updateStats(bool ProfileAvailable,
+                                     const MachineJumpTableInfo *MJTI) {
+  if (!AreStatisticsEnabled())
+    return;
 
-  return true;
+  if (MJTI)
+    updateJumpTableStats(ProfileAvailable, *MJTI);
 }
 
 char StaticDataSplitter::ID = 0;

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -668,11 +668,10 @@ getELFSectionNameForGlobal(const GlobalObject *GO, SectionKind Kind,
   }
 
   bool HasPrefix = false;
-  if (const auto *F = dyn_cast<Function>(GO)) {
-    if (std::optional<StringRef> Prefix = F->getSectionPrefix()) {
-      raw_svector_ostream(Name) << '.' << *Prefix;
-      HasPrefix = true;
-    }
+
+  if (std::optional<StringRef> Prefix = GO->getSectionPrefix()) {
+    raw_svector_ostream(Name) << '.' << *Prefix;
+    HasPrefix = true;
   }
 
   if (UniqueSectionName) {

llvm/lib/IR/Function.cpp

@@ -1164,22 +1164,6 @@ DenseSet<GlobalValue::GUID> Function::getImportGUIDs() const {
   return R;
 }
 
-void Function::setSectionPrefix(StringRef Prefix) {
-  MDBuilder MDB(getContext());
-  setMetadata(LLVMContext::MD_section_prefix,
-              MDB.createFunctionSectionPrefix(Prefix));
-}
-
-std::optional<StringRef> Function::getSectionPrefix() const {
-  if (MDNode *MD = getMetadata(LLVMContext::MD_section_prefix)) {
-    assert(cast<MDString>(MD->getOperand(0))->getString() ==
-               "function_section_prefix" &&
-           "Metadata not match");
-    return cast<MDString>(MD->getOperand(1))->getString();
-  }
-  return std::nullopt;
-}
-
 bool Function::nullPointerIsDefined() const {
   return hasFnAttribute(Attribute::NullPointerIsValid);
 }

llvm/lib/IR/Globals.cpp

@@ -18,6 +18,7 @@
 #include "llvm/IR/GlobalAlias.h"
 #include "llvm/IR/GlobalValue.h"
 #include "llvm/IR/GlobalVariable.h"
+#include "llvm/IR/MDBuilder.h"
 #include "llvm/IR/Module.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/ErrorHandling.h"
@@ -286,6 +287,24 @@ void GlobalObject::setSection(StringRef S) {
   setGlobalObjectFlag(HasSectionHashEntryBit, !S.empty());
 }
 
+void GlobalObject::setSectionPrefix(StringRef Prefix) {
+  MDBuilder MDB(getContext());
+  setMetadata(LLVMContext::MD_section_prefix,
+              MDB.createGlobalObjectSectionPrefix(Prefix));
+}
+
+std::optional<StringRef> GlobalObject::getSectionPrefix() const {
+  if (MDNode *MD = getMetadata(LLVMContext::MD_section_prefix)) {
+    [[maybe_unused]] StringRef MDName =
+        cast<MDString>(MD->getOperand(0))->getString();
+    assert((MDName == "section_prefix" ||
+            (isa<Function>(this) && MDName == "function_section_prefix")) &&
+           "Metadata not match");
+    return cast<MDString>(MD->getOperand(1))->getString();
+  }
+  return std::nullopt;
+}
+
 bool GlobalValue::isNobuiltinFnDef() const {
   const Function *F = dyn_cast<Function>(this);
   if (!F || F->empty())

llvm/lib/IR/MDBuilder.cpp

@@ -87,9 +87,9 @@ MDNode *MDBuilder::createFunctionEntryCount(
   return MDNode::get(Context, Ops);
 }
 
-MDNode *MDBuilder::createFunctionSectionPrefix(StringRef Prefix) {
-  return MDNode::get(
-      Context, {createString("function_section_prefix"), createString(Prefix)});
+MDNode *MDBuilder::createGlobalObjectSectionPrefix(StringRef Prefix) {
+  return MDNode::get(Context,
+                     {createString("section_prefix"), createString(Prefix)});
 }
 
 MDNode *MDBuilder::createRange(const APInt &Lo, const APInt &Hi) {

llvm/test/CodeGen/X86/data-section-prefix.ll

@@ -0,0 +1,27 @@
+; RUN: llc -mtriple x86_64-linux-gnu -data-sections %s -o - | FileCheck %s --check-prefix=ELF
+; RUN: llc -mtriple x86_64-linux-gnu -unique-section-names=0 -data-sections %s -o - | FileCheck %s --check-prefix=ELF-NOUNIQ
+
+; RUN: llc -mtriple x86_64-windows-msvc -data-sections %s -o - | FileCheck %s --check-prefix=COFF-MSVC
+
+; ELF: .section .data.hot.foo,
+; ELF: .section .data.bar,
+; ELF: .section .bss.unlikely.baz,
+; ELF: .section .bss.quz,
+
+; ELF-NOUNIQ: .section    .data.hot.,"aw",@progbits,unique,1
+; ELF-NOUNIQ: .section    .data,"aw",@progbits,unique,2
+; ELF-NOUNIQ: .section    .bss.unlikely.,"aw",@nobits,unique,3
+; ELF-NOUNIQ: .section    .bss,"aw",@nobits,unique,4
+
+; COFF-MSVC: .section .data,"dw",one_only,foo
+; COFF-MSVC: .section .data,"dw",one_only,bar
+; COFF-MSVC: .section .bss,"bw",one_only,baz
+; COFF-MSVC: .section .bss,"bw",one_only,quz
+
+@foo = global i32 1, !section_prefix !0
+@bar = global i32 2
+@baz = global i32 0, !section_prefix !1
+@quz = global i32 0
+
+!0 = !{!"section_prefix", !"hot"}
+!1 = !{!"section_prefix", !"unlikely"}

llvm/test/Transforms/CodeGenPrepare/X86/section-samplepgo.ll

@@ -34,8 +34,8 @@ define void @cold_func() !prof !16 {
   ret void
 }
 
-; CHECK: ![[HOT_ID]] = !{!"function_section_prefix", !"hot"}
-; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[HOT_ID]] = !{!"section_prefix", !"hot"}
+; CHECK: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 !llvm.module.flags = !{!1}
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}

llvm/test/Transforms/CodeGenPrepare/X86/section.ll

@@ -66,8 +66,8 @@ define void @cold_func3() !prof !16 {
   ret void
 }
 
-; CHECK: ![[HOT_ID]] = !{!"function_section_prefix", !"hot"}
-; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[HOT_ID]] = !{!"section_prefix", !"hot"}
+; CHECK: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 !llvm.module.flags = !{!1}
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}

llvm/test/Transforms/HotColdSplit/coldentrycount.ll

@@ -27,9 +27,9 @@ declare void @sink() cold
 ; CHECK: define {{.*}} @fun.cold.1{{.*}} ![[PROF:[0-9]+]] {{.*}}section_prefix ![[UNLIKELY:[0-9]+]]
 
 ; CHECK: ![[HOTPROF]] = !{!"function_entry_count", i64 100}
-; CHECK: ![[LIKELY]] = !{!"function_section_prefix", !"hot"}
+; CHECK: ![[LIKELY]] = !{!"section_prefix", !"hot"}
 ; CHECK: ![[PROF]] = !{!"function_entry_count", i64 0}
-; CHECK: ![[UNLIKELY]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[UNLIKELY]] = !{!"section_prefix", !"unlikely"}
 
 !llvm.module.flags = !{!0}
 !0 = !{i32 1, !"ProfileSummary", !1}

llvm/test/Transforms/SampleProfile/section-accurate-samplepgo.ll

@@ -36,11 +36,11 @@ attributes #1 = { "use-sample-profile" }
 
 ; CHECK: ![[NOPROFILE_ID]] = !{!"function_entry_count", i64 -1}
 ; CHECK: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
-; CHECK: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; CHECK: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 ; UNKNOWN: ![[NOPROFILE_ID]] = !{!"function_entry_count", i64 -1}
-; UNKNOWN: ![[UNKNOWN_ID]] = !{!"function_section_prefix", !"unknown"}
+; UNKNOWN: ![[UNKNOWN_ID]] = !{!"section_prefix", !"unknown"}
 ; ACCURATE: ![[ZERO_ID]] = !{!"function_entry_count", i64 0}
-; ACCURATE: ![[COLD_ID]] = !{!"function_section_prefix", !"unlikely"}
+; ACCURATE: ![[COLD_ID]] = !{!"section_prefix", !"unlikely"}
 !llvm.module.flags = !{!1}
 !1 = !{i32 1, !"ProfileSummary", !2}
 !2 = !{!3, !4, !5, !6, !7, !8, !9, !10}