[AsmPrinter][TargetLowering]Place a hot jump table into a hot-suffixed section

Author: mingmingl-llvm

llvm/include/llvm/CodeGen/AsmPrinter.h

@@ -453,6 +453,10 @@ class AsmPrinter : public MachineFunctionPass {
   /// function to the current output stream.
   virtual void emitJumpTableInfo();
 
+  virtual void emitJumpTables(const std::vector<unsigned> &JumpTableIndices,
+                              MCSection *JumpTableSection, bool JTInDiffSection,
+                              const MachineJumpTableInfo &MJTI);
+
   /// Emit the specified global variable to the .s file.
   virtual void emitGlobalVariable(const GlobalVariable *GV);
 
@@ -892,10 +896,10 @@ class AsmPrinter : public MachineFunctionPass {
   // Internal Implementation Details
   //===------------------------------------------------------------------===//
 
-  void emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
+  void emitJumpTableEntry(const MachineJumpTableInfo &MJTI,
                           const MachineBasicBlock *MBB, unsigned uid) const;
 
-  void emitJumpTableSizesSection(const MachineJumpTableInfo *MJTI,
+  void emitJumpTableSizesSection(const MachineJumpTableInfo &MJTI,
                                  const Function &F) const;
 
   void emitLLVMUsedList(const ConstantArray *InitList);

llvm/include/llvm/CodeGen/TargetLoweringObjectFileImpl.h

@@ -74,6 +74,9 @@ class TargetLoweringObjectFileELF : public TargetLoweringObjectFile {
 
   MCSection *getSectionForJumpTable(const Function &F,
                                     const TargetMachine &TM) const override;
+  MCSection *
+  getSectionForJumpTable(const Function &F, const TargetMachine &TM,
+                         const MachineJumpTableEntry *JTE) const override;
   MCSection *getSectionForLSDA(const Function &F, const MCSymbol &FnSym,
                                const TargetMachine &TM) const override;
 

llvm/include/llvm/Target/TargetLoweringObjectFile.h

@@ -27,6 +27,7 @@ class Function;
 class GlobalObject;
 class GlobalValue;
 class MachineBasicBlock;
+class MachineJumpTableEntry;
 class MachineModuleInfo;
 class Mangler;
 class MCContext;
@@ -132,6 +133,10 @@ class TargetLoweringObjectFile : public MCObjectFileInfo {
 
   virtual MCSection *getSectionForJumpTable(const Function &F,
                                             const TargetMachine &TM) const;
+  virtual MCSection *
+  getSectionForJumpTable(const Function &F, const TargetMachine &TM,
+                         const MachineJumpTableEntry *JTE) const;
+
   virtual MCSection *getSectionForLSDA(const Function &, const MCSymbol &,
                                        const TargetMachine &) const {
     return LSDASection;

llvm/lib/CodeGen/AsmPrinter/AsmPrinter.cpp

@@ -168,6 +168,11 @@ static cl::opt<bool> BBAddrMapSkipEmitBBEntries(
              "unnecessary for some PGOAnalysisMap features."),
     cl::Hidden, cl::init(false));
 
+static cl::opt<bool>
+    EmitStaticDataHotnessSuffix("emit-static-data-hotness-suffix", cl::Hidden,
+                                cl::init(false), cl::ZeroOrMore,
+                                cl::desc("Emit static data hotness suffix"));
+
 static cl::opt<bool> EmitJumpTableSizesSection(
     "emit-jump-table-sizes-section",
     cl::desc("Emit a section containing jump table addresses and sizes"),
@@ -2861,7 +2866,6 @@ void AsmPrinter::emitConstantPool() {
 // Print assembly representations of the jump tables used by the current
 // function.
 void AsmPrinter::emitJumpTableInfo() {
-  const DataLayout &DL = MF->getDataLayout();
   const MachineJumpTableInfo *MJTI = MF->getJumpTableInfo();
   if (!MJTI) return;
   if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_Inline) return;
@@ -2876,42 +2880,88 @@ void AsmPrinter::emitJumpTableInfo() {
       MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 ||
           MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference64,
       F);
+
+  if (!EmitStaticDataHotnessSuffix) {
+    std::vector<unsigned> JumpTableIndices;
+    for (unsigned JTI = 0, e = JT.size(); JTI != e; ++JTI)
+      JumpTableIndices.push_back(JTI);
+    // Prior code in this function verifies JT is not empty. Use JT[0] directly.
+    emitJumpTables(JumpTableIndices, TLOF.getSectionForJumpTable(F, TM),
+                   JTInDiffSection, *MJTI);
+    return;
+  }
+
+  // Iterate all jump tables, put them into two vectors, hot and lukewarm
+  std::vector<unsigned> HotOrWarmJumpTableIndices, ColdJumpTableIndices;
+
+  for (unsigned JTI = 0, e = JT.size(); JTI != e; ++JTI) {
+    if (JT[JTI].Hotness == llvm::DataHotness::Cold)
+      ColdJumpTableIndices.push_back(JTI);
+    else
+      HotOrWarmJumpTableIndices.push_back(JTI);
+  }
+
+  if (!HotOrWarmJumpTableIndices.empty())
+    emitJumpTables(HotOrWarmJumpTableIndices,
+                   TLOF.getSectionForJumpTable(
+                       F, TM, &JT[*HotOrWarmJumpTableIndices.begin()]),
+                   JTInDiffSection, *MJTI);
+
+  if (!ColdJumpTableIndices.empty())
+    emitJumpTables(
+        ColdJumpTableIndices,
+        TLOF.getSectionForJumpTable(F, TM, &JT[*ColdJumpTableIndices.begin()]),
+        JTInDiffSection, *MJTI);
+
+  return;
+}
+
+void AsmPrinter::emitJumpTables(const std::vector<unsigned> &JumpTableIndices,
+                                MCSection *JumpTableSection,
+                                bool JTInDiffSection,
+                                const MachineJumpTableInfo &MJTI) {
+  if (JumpTableIndices.empty())
+    return;
+
+  const DataLayout &DL = MF->getDataLayout();
   if (JTInDiffSection) {
-    // Drop it in the readonly section.
-    MCSection *ReadOnlySection = TLOF.getSectionForJumpTable(F, TM);
-    OutStreamer->switchSection(ReadOnlySection);
+    OutStreamer->switchSection(JumpTableSection);
   }
 
-  emitAlignment(Align(MJTI->getEntryAlignment(DL)));
+  emitAlignment(Align(MJTI.getEntryAlignment(MF->getDataLayout())));
 
   // Jump tables in code sections are marked with a data_region directive
   // where that's supported.
   if (!JTInDiffSection)
     OutStreamer->emitDataRegion(MCDR_DataRegionJT32);
 
-  for (unsigned JTI = 0, e = JT.size(); JTI != e; ++JTI) {
-    const std::vector<MachineBasicBlock*> &JTBBs = JT[JTI].MBBs;
+  const auto &JT = MJTI.getJumpTables();
+  for (unsigned Index = 0, e = JumpTableIndices.size(); Index != e; ++Index) {
+    const std::vector<MachineBasicBlock *> &JTBBs =
+        JT[JumpTableIndices[Index]].MBBs;
 
     // If this jump table was deleted, ignore it.
-    if (JTBBs.empty()) continue;
+    if (JTBBs.empty())
+      continue;
 
     // For the EK_LabelDifference32 entry, if using .set avoids a relocation,
     /// emit a .set directive for each unique entry.
-    if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 &&
+    if (MJTI.getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 &&
         MAI->doesSetDirectiveSuppressReloc()) {
-      SmallPtrSet<const MachineBasicBlock*, 16> EmittedSets;
+      SmallPtrSet<const MachineBasicBlock *, 16> EmittedSets;
       const TargetLowering *TLI = MF->getSubtarget().getTargetLowering();
-      const MCExpr *Base = TLI->getPICJumpTableRelocBaseExpr(MF,JTI,OutContext);
+      const MCExpr *Base = TLI->getPICJumpTableRelocBaseExpr(
+          MF, JumpTableIndices[Index], OutContext);
       for (const MachineBasicBlock *MBB : JTBBs) {
         if (!EmittedSets.insert(MBB).second)
           continue;
 
         // .set LJTSet, LBB32-base
         const MCExpr *LHS =
-          MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
-        OutStreamer->emitAssignment(GetJTSetSymbol(JTI, MBB->getNumber()),
-                                    MCBinaryExpr::createSub(LHS, Base,
-                                                            OutContext));
+            MCSymbolRefExpr::create(MBB->getSymbol(), OutContext);
+        OutStreamer->emitAssignment(
+            GetJTSetSymbol(JumpTableIndices[Index], MBB->getNumber()),
+            MCBinaryExpr::createSub(LHS, Base, OutContext));
       }
     }
 
@@ -2923,27 +2973,27 @@ void AsmPrinter::emitJumpTableInfo() {
       // FIXME: This doesn't have to have any specific name, just any randomly
       // named and numbered local label started with 'l' would work.  Simplify
       // GetJTISymbol.
-      OutStreamer->emitLabel(GetJTISymbol(JTI, true));
+      OutStreamer->emitLabel(GetJTISymbol(JumpTableIndices[Index], true));
 
-    MCSymbol* JTISymbol = GetJTISymbol(JTI);
+    MCSymbol *JTISymbol = GetJTISymbol(JumpTableIndices[Index]);
     OutStreamer->emitLabel(JTISymbol);
 
     // Defer MCAssembler based constant folding due to a performance issue. The
     // label differences will be evaluated at write time.
     for (const MachineBasicBlock *MBB : JTBBs)
-      emitJumpTableEntry(MJTI, MBB, JTI);
+      emitJumpTableEntry(MJTI, MBB, JumpTableIndices[Index]);
   }
 
   if (EmitJumpTableSizesSection)
-    emitJumpTableSizesSection(MJTI, F);
+    emitJumpTableSizesSection(MJTI, MF->getFunction());
 
   if (!JTInDiffSection)
     OutStreamer->emitDataRegion(MCDR_DataRegionEnd);
 }
 
-void AsmPrinter::emitJumpTableSizesSection(const MachineJumpTableInfo *MJTI,
+void AsmPrinter::emitJumpTableSizesSection(const MachineJumpTableInfo &MJTI,
                                            const Function &F) const {
-  const std::vector<MachineJumpTableEntry> &JT = MJTI->getJumpTables();
+  const std::vector<MachineJumpTableEntry> &JT = MJTI.getJumpTables();
 
   if (JT.empty())
     return;
@@ -2991,17 +3041,17 @@ void AsmPrinter::emitJumpTableSizesSection(const MachineJumpTableInfo *MJTI,
 
 /// EmitJumpTableEntry - Emit a jump table entry for the specified MBB to the
 /// current stream.
-void AsmPrinter::emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
+void AsmPrinter::emitJumpTableEntry(const MachineJumpTableInfo &MJTI,
                                     const MachineBasicBlock *MBB,
                                     unsigned UID) const {
   assert(MBB && MBB->getNumber() >= 0 && "Invalid basic block");
   const MCExpr *Value = nullptr;
-  switch (MJTI->getEntryKind()) {
+  switch (MJTI.getEntryKind()) {
   case MachineJumpTableInfo::EK_Inline:
     llvm_unreachable("Cannot emit EK_Inline jump table entry");
   case MachineJumpTableInfo::EK_Custom32:
     Value = MF->getSubtarget().getTargetLowering()->LowerCustomJumpTableEntry(
-        MJTI, MBB, UID, OutContext);
+        &MJTI, MBB, UID, OutContext);
     break;
   case MachineJumpTableInfo::EK_BlockAddress:
     // EK_BlockAddress - Each entry is a plain address of block, e.g.:
@@ -3035,7 +3085,7 @@ void AsmPrinter::emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
     // If the .set directive avoids relocations, this is emitted as:
     //      .set L4_5_set_123, LBB123 - LJTI1_2
     //      .word L4_5_set_123
-    if (MJTI->getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 &&
+    if (MJTI.getEntryKind() == MachineJumpTableInfo::EK_LabelDifference32 &&
         MAI->doesSetDirectiveSuppressReloc()) {
       Value = MCSymbolRefExpr::create(GetJTSetSymbol(UID, MBB->getNumber()),
                                       OutContext);
@@ -3051,7 +3101,7 @@ void AsmPrinter::emitJumpTableEntry(const MachineJumpTableInfo *MJTI,
 
   assert(Value && "Unknown entry kind!");
 
-  unsigned EntrySize = MJTI->getEntrySize(getDataLayout());
+  unsigned EntrySize = MJTI.getEntrySize(getDataLayout());
   OutStreamer->emitValue(Value, EntrySize);
 }
 

llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp

@@ -24,6 +24,7 @@
 #include "llvm/CodeGen/BasicBlockSectionUtils.h"
 #include "llvm/CodeGen/MachineBasicBlock.h"
 #include "llvm/CodeGen/MachineFunction.h"
+#include "llvm/CodeGen/MachineJumpTableInfo.h"
 #include "llvm/CodeGen/MachineModuleInfo.h"
 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
 #include "llvm/IR/Comdat.h"
@@ -642,9 +643,11 @@ static StringRef getSectionPrefixForGlobal(SectionKind Kind, bool IsLarge) {
 static SmallString<128>
 getELFSectionNameForGlobal(const GlobalObject *GO, SectionKind Kind,
                            Mangler &Mang, const TargetMachine &TM,
-                           unsigned EntrySize, bool UniqueSectionName) {
+                           unsigned EntrySize, bool UniqueSectionName,
+                           const MachineJumpTableEntry *JTE) {
   SmallString<128> Name =
       getSectionPrefixForGlobal(Kind, TM.isLargeGlobalValue(GO));
+
   if (Kind.isMergeableCString()) {
     // We also need alignment here.
     // FIXME: this is getting the alignment of the character, not the
@@ -663,7 +666,11 @@ getELFSectionNameForGlobal(const GlobalObject *GO, SectionKind Kind,
 
   bool HasPrefix = false;
   if (const auto *F = dyn_cast<Function>(GO)) {
-    if (std::optional<StringRef> Prefix = F->getSectionPrefix()) {
+    // Jump table hotness takes precedence over its enclosing function's hotness
+    // if both are available.
+    if (JTE && JTE->Hotness == DataHotness::Hot)
+      raw_svector_ostream(Name) << ".hot";
+    else if (std::optional<StringRef> Prefix = F->getSectionPrefix()) {
       raw_svector_ostream(Name) << '.' << *Prefix;
       HasPrefix = true;
     }
@@ -761,8 +768,8 @@ calcUniqueIDUpdateFlagsAndSize(const GlobalObject *GO, StringRef SectionName,
   // implicitly for this symbol e.g. .rodata.str1.1, then we don't need
   // to unique the section as the entry size for this symbol will be
   // compatible with implicitly created sections.
-  SmallString<128> ImplicitSectionNameStem =
-      getELFSectionNameForGlobal(GO, Kind, Mang, TM, EntrySize, false);
+  SmallString<128> ImplicitSectionNameStem = getELFSectionNameForGlobal(
+      GO, Kind, Mang, TM, EntrySize, false, /*MJTE=*/nullptr);
   if (SymbolMergeable &&
       Ctx.isELFImplicitMergeableSectionNamePrefix(SectionName) &&
       SectionName.starts_with(ImplicitSectionNameStem))
@@ -862,7 +869,8 @@ MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
 static MCSectionELF *selectELFSectionForGlobal(
     MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
     const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
-    unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
+    unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol,
+    const MachineJumpTableEntry *MJTE = nullptr) {
 
   auto [Group, IsComdat, ExtraFlags] = getGlobalObjectInfo(GO, TM);
   Flags |= ExtraFlags;
@@ -881,7 +889,7 @@ static MCSectionELF *selectELFSectionForGlobal(
     }
   }
   SmallString<128> Name = getELFSectionNameForGlobal(
-      GO, Kind, Mang, TM, EntrySize, UniqueSectionName);
+      GO, Kind, Mang, TM, EntrySize, UniqueSectionName, MJTE);
 
   // Use 0 as the unique ID for execute-only text.
   if (Kind.isExecuteOnly())
@@ -955,6 +963,12 @@ MCSection *TargetLoweringObjectFileELF::getUniqueSectionForFunction(
 
 MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
     const Function &F, const TargetMachine &TM) const {
+  return getSectionForJumpTable(F, TM, nullptr);
+}
+
+MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
+    const Function &F, const TargetMachine &TM,
+    const MachineJumpTableEntry *JTE) const {
   // If the function can be removed, produce a unique section so that
   // the table doesn't prevent the removal.
   const Comdat *C = F.getComdat();
@@ -965,7 +979,7 @@ MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
   return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
                                    getMangler(), TM, EmitUniqueSection,
                                    ELF::SHF_ALLOC, &NextUniqueID,
-                                   /* AssociatedSymbol */ nullptr);
+                                   /* AssociatedSymbol */ nullptr, JTE);
 }
 
 MCSection *TargetLoweringObjectFileELF::getSectionForLSDA(

llvm/lib/CodeGen/TargetPassConfig.cpp

@@ -263,6 +263,11 @@ static cl::opt<bool>
     GCEmptyBlocks("gc-empty-basic-blocks", cl::init(false), cl::Hidden,
                   cl::desc("Enable garbage-collecting empty basic blocks"));
 
+/// Enable the static data splitter pass.
+static cl::opt<bool> SplitStaticData(
+    "split-static-data", cl::Hidden, cl::init(false),
+    cl::desc("Split static data sections using profile information"));
+
 /// Allow standard passes to be disabled by command line options. This supports
 /// simple binary flags that either suppress the pass or do nothing.
 /// i.e. -disable-mypass=false has no effect.
@@ -1256,8 +1261,9 @@ void TargetPassConfig::addMachinePasses() {
                "performance.\n";
       }
     }
-    addPass(createStaticDataSplitterPass());
     addPass(createMachineFunctionSplitterPass());
+    if (SplitStaticData)
+      addPass(createStaticDataSplitterPass());
   }
   // We run the BasicBlockSections pass if either we need BB sections or BB
   // address map (or both).

llvm/lib/Target/TargetLoweringObjectFile.cpp

@@ -348,6 +348,12 @@ TargetLoweringObjectFile::SectionForGlobal(const GlobalObject *GO,
 
 MCSection *TargetLoweringObjectFile::getSectionForJumpTable(
     const Function &F, const TargetMachine &TM) const {
+  return getSectionForJumpTable(F, TM, nullptr);
+}
+
+MCSection *TargetLoweringObjectFile::getSectionForJumpTable(
+    const Function &F, const TargetMachine &TM,
+    const MachineJumpTableEntry *JTE) const {
   Align Alignment(1);
   return getSectionForConstant(F.getDataLayout(),
                                SectionKind::getReadOnly(), /*C=*/nullptr,

llvm/test/CodeGen/X86/jump-table-partition.ll

@@ -2,18 +2,22 @@
 ; requires: asserts
 
 ; RUN: llc -stop-after=block-placement %s -o - | llc --run-pass=static-data-splitter -stats -x mir -o - 2>&1 | FileCheck %s --check-prefix=STAT
+; RUN: llc -enable-split-machine-functions -split-static-data --function-sections -data-sections %s -o - 2>&1 | FileCheck %s --check-prefix=SECTION
 
 ; `func_with_hot_jumptable` contains a hot jump table and `func_with_cold_jumptable` contains a cold one. 
 ; `func_without_entry_count` simulates the functions without profile information (e.g., not instrumented or not profiled),
 ; it's jump table hotness is unknown and regarded as hot conservatively.
 ;
 ; Tests stat messages are expected.
-; TODO: Update test to verify section suffixes when target-lowering and assembler changes are implemented.
-;
 ; STAT-DAG: 1 static-data-splitter - Number of cold jump tables seen
 ; STAT-DAG: 1 static-data-splitter - Number of hot jump tables seen
 ; STAT-DAG: 1 static-data-splitter - Number of jump tables with unknown hotness
 
+; TODO: Construct a test case where a hot function has a cold jump table.
+; SECTION: .section .rodata.hot.func_with_hot_jumptable
+; SECTION: .section .rodata.unlikely.func_with_cold_jumptable
+; SECTION: .section .rodata.hot.func_without_entry_count
+
 target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"