[CSSPGO][llvm-profgen] Instruction symbolization

[wlei]

Summary

This stack of changes introduces llvm-profgen utility which generates a profile data file from given perf script data files for sample-based PGO. It’s part of(not only) the CSSPGO work. Specifically to support context-sensitive with/without pseudo probe profile, it implements a series of functionalities including perf trace parsing, instruction symbolization, LBR stack/call frame stack unwinding, pseudo probe decoding, etc. Also high throughput is achieved by multiple levels of sample aggregation and compatible format with one stop is generated at the end. Please refer to: https://groups.google.com/g/llvm-dev/c/1p1rdYbL93s for the CSSPGO RFC.

This change adds the support of instruction symbolization. Given the RVA on an instruction pointer, a full calling context can be printed side-by-side with the disassembly code.
E.g.

Disassembly of section .text [0x0, 0x4a]:

<funcA>:
    0:	mov	eax, edi                           funcA:0
    2:	mov	ecx, dword ptr [rip]               funcLeaf:2 @ funcA:1
    8:	lea	edx, [rcx + 3]                     fib:2 @ funcLeaf:2 @ funcA:1
    b:	cmp	ecx, 3                             fib:2 @ funcLeaf:2 @ funcA:1
    e:	cmovl	edx, ecx                           fib:2 @ funcLeaf:2 @ funcA:1
   11:	sub	eax, edx                           funcLeaf:2 @ funcA:1
   13:	ret                                        funcA:2
   14:	nop	word ptr cs:[rax + rax]
   1e:	nop

<funcLeaf>:
   20:	mov	eax, edi                           funcLeaf:1
   22:	mov	ecx, dword ptr [rip]               funcLeaf:2
   28:	lea	edx, [rcx + 3]                     fib:2 @ funcLeaf:2
   2b:	cmp	ecx, 3                             fib:2 @ funcLeaf:2
   2e:	cmovl	edx, ecx                           fib:2 @ funcLeaf:2
   31:	sub	eax, edx                           funcLeaf:2
   33:	ret                                        funcLeaf:3
   34:	nop	word ptr cs:[rax + rax]
   3e:	nop

<fib>:
   40:	lea	eax, [rdi + 3]                     fib:2
   43:	cmp	edi, 3                             fib:2
   46:	cmovl	eax, edi                           fib:2
   49:	ret                                        fib:8

Test Plan:
ninja check-llvm

[wlei]

rebase

[wenlei]

llvm/tools/llvm-profgen/CallContext.h

22

Name it FrameLocation? SourceLocation sounds too general and not different from LineLocation.

25

Name it FrameLocationStack? Also would be good to update the comment to be accurate - this is not a caller, callee pair.

41

std::ostringstream is probably better since there can be quite a few appendings. Same for getReversedLocWithContext.

[wlei]

address reviewers' comments and rebase

[wlei]

fix lint

[wlei]

rebase

[wlei]

rebase and fix clang-tidy warning

[wlei]

miss one clang-tidy warning, fix it

[wlei]

Fix clang-tidy and the wrong type which caused an overflow

[wmi]

llvm/tools/llvm-profgen/ProfiledBinary.cpp

289

Add some message for the assert(this == IP.Binary && "...");

[wlei]

[NFC]Add description to an assertion

llvm/test/tools/llvm-profgen/symbolize.ll

+; REQUIRES: x86-registered-target
+; RUN: llc -filetype=obj %s -o %t
+; RUN: llvm-profgen --binary=%t --perfscript=%s --output=%t1 --show-disassembly -x86-asm-syntax=intel --show-source-locations | FileCheck %s --match-full-lines
+
+; CHECK: Disassembly of section .text [0x0, 0x4a]:
+; CHECK: <funcA>:
+; CHECK:        0:  mov eax, edi                         funcA:0
+; CHECK:        2:  mov ecx, dword ptr [rip]             funcLeaf:2 @ funcA:1
+; CHECK:        8:  lea edx, [rcx + 3]                   fib:2 @ funcLeaf:2 @ funcA:1
+; CHECK:        b:  cmp ecx, 3                           fib:2 @ funcLeaf:2 @ funcA:1
+; CHECK:        e:  cmovl edx, ecx                       fib:2 @ funcLeaf:2 @ funcA:1
+; CHECK:       11:  sub eax, edx                         funcLeaf:2 @ funcA:1
+; CHECK:       13:  ret                                  funcA:2
+; CHECK:       14:  nop word ptr cs:[rax + rax]
+; CHECK:       1e:  nop
+; CHECK: <funcLeaf>:
+; CHECK:      20: mov eax, edi                           funcLeaf:1
+; CHECK:      22: mov ecx, dword ptr [rip]               funcLeaf:2
+; CHECK:      28: lea edx, [rcx + 3]                     fib:2 @ funcLeaf:2
+; CHECK:      2b: cmp ecx, 3                             fib:2 @ funcLeaf:2
+; CHECK:      2e: cmovl edx, ecx                         fib:2 @ funcLeaf:2
+; CHECK:      31: sub eax, edx                           funcLeaf:2
+; CHECK:      33: ret                                    funcLeaf:3
+; CHECK:      34: nop word ptr cs:[rax + rax]
+; CHECK:      3e: nop
+; CHECK: <fib>:
+; CHECK:      40: lea eax, [rdi + 3]                     fib:2
+; CHECK:      43: cmp edi, 3                             fib:2
+; CHECK:      46: cmovl eax, edi                         fib:2
+; CHECK:      49: ret                                    fib:8
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+@factor = dso_local global i32 3
+
+define dso_local i32 @funcA(i32 %x) !dbg !12 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %x, metadata !16, metadata !DIExpression()), !dbg !18
+  call void @llvm.dbg.value(metadata i32 %x, metadata !19, metadata !DIExpression()), !dbg !22
+  %0 = load volatile i32, i32* @factor, align 4, !dbg !24, !tbaa !25
+  call void @llvm.dbg.value(metadata i32 %0, metadata !29, metadata !DIExpression()), !dbg !32
+  %cmp.i.i = icmp slt i32 %0, 3, !dbg !34
+  %add.i.i = add nsw i32 %0, 3, !dbg !36
+  %retval.0.i.i = select i1 %cmp.i.i, i32 %0, i32 %add.i.i, !dbg !36
+  %sub.i = sub nsw i32 %x, %retval.0.i.i, !dbg !37
+  call void @llvm.dbg.value(metadata i32 %sub.i, metadata !19, metadata !DIExpression()), !dbg !22
+  call void @llvm.dbg.value(metadata i32 %sub.i, metadata !17, metadata !DIExpression()), !dbg !18
+  ret i32 %sub.i, !dbg !38
+}
+
+define dso_local i32 @funcLeaf(i32 %x) !dbg !20 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %x, metadata !19, metadata !DIExpression()), !dbg !39
+  %0 = load volatile i32, i32* @factor, align 4, !dbg !40, !tbaa !25
+  call void @llvm.dbg.value(metadata i32 %0, metadata !29, metadata !DIExpression()), !dbg !41
+  %cmp.i = icmp slt i32 %0, 3, !dbg !43
+  %add.i = add nsw i32 %0, 3, !dbg !44
+  %retval.0.i = select i1 %cmp.i, i32 %0, i32 %add.i, !dbg !44
+  %sub = sub nsw i32 %x, %retval.0.i, !dbg !45
+  call void @llvm.dbg.value(metadata i32 %sub, metadata !19, metadata !DIExpression()), !dbg !39
+  ret i32 %sub, !dbg !46
+}
+
+define dso_local i32 @fib(i32 %x) !dbg !30 {
+entry:
+  call void @llvm.dbg.value(metadata i32 %x, metadata !29, metadata !DIExpression()), !dbg !47
+  %cmp = icmp slt i32 %x, 3, !dbg !48
+  %add = add nsw i32 %x, 3, !dbg !49
+  %retval.0 = select i1 %cmp, i32 %x, i32 %add, !dbg !49
+  ret i32 %retval.0, !dbg !50
+}
+
+declare void @llvm.dbg.value(metadata, metadata, metadata) #2
+
+!llvm.dbg.cu = !{!2}
+!llvm.module.flags = !{!8, !9, !10}
+
+!1 = distinct !DIGlobalVariable(name: "factor", scope: !2, file: !3, line: 3, type: !6, isLocal: false, isDefinition: true)
+!2 = distinct !DICompileUnit(language: DW_LANG_C99, file: !3, emissionKind: FullDebug)
+!3 = !DIFile(filename: "test.c", directory: "test")
+!4 = !{}
+!6 = !DIDerivedType(tag: DW_TAG_volatile_type, baseType: !7)
+!7 = !DIBasicType(name: "int", size: 32, encoding: DW_ATE_signed)
+!8 = !{i32 7, !"Dwarf Version", i32 4}
+!9 = !{i32 2, !"Debug Info Version", i32 3}
+!10 = !{i32 1, !"wchar_size", i32 4}
+!12 = distinct !DISubprogram(name: "funcA", scope: !3, file: !3, line: 6, type: !13, scopeLine: 6, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !15)
+!13 = !DISubroutineType(types: !14)
+!14 = !{!7, !7}
+!15 = !{!16, !17}
+!16 = !DILocalVariable(name: "x", arg: 1, scope: !12, file: !3, line: 6, type: !7)
+!17 = !DILocalVariable(name: "r", scope: !12, file: !3, line: 7, type: !7)
+!18 = !DILocation(line: 0, scope: !12)
+!19 = !DILocalVariable(name: "x", arg: 1, scope: !20, file: !3, line: 22, type: !7)
+!20 = distinct !DISubprogram(name: "funcLeaf", scope: !3, file: !3, line: 22, type: !13, scopeLine: 23, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !21)
+!21 = !{!19}
+!22 = !DILocation(line: 0, scope: !20, inlinedAt: !23)
+!23 = distinct !DILocation(line: 7, column: 11, scope: !12)
+!24 = !DILocation(line: 24, column: 12, scope: !20, inlinedAt: !23)
+!25 = !{!26, !26, i64 0}
+!26 = !{!"int", !27, i64 0}
+!27 = !{!"omnipotent char", !28, i64 0}
+!28 = !{!"Simple C/C++ TBAA"}
+!29 = !DILocalVariable(name: "x", arg: 1, scope: !30, file: !3, line: 11, type: !7)
+!30 = distinct !DISubprogram(name: "fib", scope: !3, file: !3, line: 11, type: !13, scopeLine: 12, flags: DIFlagPrototyped | DIFlagAllCallsDescribed, spFlags: DISPFlagDefinition | DISPFlagOptimized, unit: !2, retainedNodes: !31)
+!31 = !{!29}
+!32 = !DILocation(line: 0, scope: !30, inlinedAt: !33)
+!33 = distinct !DILocation(line: 24, column: 8, scope: !20, inlinedAt: !23)
+!34 = !DILocation(line: 13, column: 9, scope: !35, inlinedAt: !33)
+!35 = distinct !DILexicalBlock(scope: !30, file: !3, line: 13, column: 7)
+!36 = !DILocation(line: 13, column: 7, scope: !30, inlinedAt: !33)
+!37 = !DILocation(line: 24, column: 5, scope: !20, inlinedAt: !23)
+!38 = !DILocation(line: 8, column: 3, scope: !12)
+!39 = !DILocation(line: 0, scope: !20)
+!40 = !DILocation(line: 24, column: 12, scope: !20)
+!41 = !DILocation(line: 0, scope: !30, inlinedAt: !42)
+!42 = distinct !DILocation(line: 24, column: 8, scope: !20)
+!43 = !DILocation(line: 13, column: 9, scope: !35, inlinedAt: !42)
+!44 = !DILocation(line: 13, column: 7, scope: !30, inlinedAt: !42)
+!45 = !DILocation(line: 24, column: 5, scope: !20)
+!46 = !DILocation(line: 25, column: 3, scope: !20)
+!47 = !DILocation(line: 0, scope: !30)
+!48 = !DILocation(line: 13, column: 9, scope: !35)
+!49 = !DILocation(line: 13, column: 7, scope: !30)
+!50 = !DILocation(line: 19, column: 1, scope: !30)

llvm/tools/llvm-profgen/CMakeLists.txt

 include_directories(
   ${LLVM_MAIN_SRC_DIR}/lib/Target/X86
   ${LLVM_BINARY_DIR}/lib/Target/X86
   )
 set(LLVM_LINK_COMPONENTS
   AllTargetsDescs
   AllTargetsDisassemblers
   Core
   MC
   MCDisassembler
   Object
   Support
+  Symbolize
   )
 
 add_llvm_tool(llvm-profgen
   llvm-profgen.cpp
   PerfReader.cpp
   ProfiledBinary.cpp
   )

llvm/tools/llvm-profgen/CallContext.h

+//===-- CallContext.h - Call Context Handler ---------------------*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_TOOLS_LLVM_PROFGEN_CALLCONTEXT_H
+#define LLVM_TOOLS_LLVM_PROFGEN_CALLCONTEXT_H
+
+#include "llvm/ProfileData/SampleProf.h"
+#include <sstream>
+#include <string>
+#include <vector>
+
+namespace llvm {
+namespace sampleprof {
+
+// Function name, LineLocation
+typedef std::pair<std::string, LineLocation> FrameLocation;
+
+typedef SmallVector<FrameLocation, 4> FrameLocationStack;
+
+inline std::string getCallSite(const FrameLocation &Callsite) {
+  std::string CallsiteStr = Callsite.first;
+  CallsiteStr += ":";
+  CallsiteStr += Twine(Callsite.second.LineOffset).str();
+  if (Callsite.second.Discriminator > 0) {
+    CallsiteStr += ".";
+    CallsiteStr += Twine(Callsite.second.Discriminator).str();
+  }
+  return CallsiteStr;
+}
+
+// TODO: This operation is expansive. If it ever gets called multiple times we
+// may think of making a class wrapper with internal states for it.
+inline std::string getLocWithContext(const FrameLocationStack &Context) {
+  std::ostringstream OContextStr;
+  for (const auto &Callsite : Context) {
+    if (OContextStr.str().size())
+      OContextStr << " @ ";
+    OContextStr << getCallSite(Callsite);
+  }
+  return OContextStr.str();
+}
+
+// Reverse call context, i.e., in the order of callee frames to caller frames,
+// is useful during instruction printing or pseudo probe printing.
+inline std::string
+getReversedLocWithContext(const FrameLocationStack &Context) {
+  std::ostringstream OContextStr;
+  for (const auto &Callsite : reverse(Context)) {
+    if (OContextStr.str().size())
+      OContextStr << " @ ";
+    OContextStr << getCallSite(Callsite);
+  }
+  return OContextStr.str();
+}
+
+} // end namespace sampleprof
+} // end namespace llvm
+
+#endif

llvm/tools/llvm-profgen/ProfiledBinary.h

 //===-- ProfiledBinary.h - Binary decoder -----------------------*- 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
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_TOOLS_LLVM_PROFGEN_PROFILEDBINARY_H
 #define LLVM_TOOLS_LLVM_PROFGEN_PROFILEDBINARY_H
+
+#include "CallContext.h"
 #include "llvm/ADT/StringRef.h"
+#include "llvm/DebugInfo/Symbolize/Symbolize.h"
 #include "llvm/MC/MCAsmInfo.h"
 #include "llvm/MC/MCContext.h"
 #include "llvm/MC/MCDisassembler/MCDisassembler.h"
 #include "llvm/MC/MCInst.h"
 #include "llvm/MC/MCInstPrinter.h"
 #include "llvm/MC/MCInstrAnalysis.h"
 #include "llvm/MC/MCInstrInfo.h"
 #include "llvm/MC/MCObjectFileInfo.h"
 #include "llvm/MC/MCRegisterInfo.h"
 #include "llvm/MC/MCSubtargetInfo.h"
 #include "llvm/MC/MCTargetOptions.h"
 #include "llvm/Object/ELFObjectFile.h"
 #include "llvm/Support/Path.h"
 #include <set>
 #include <string>
 #include <unordered_map>
 #include <unordered_set>
 #include <vector>
 
 using namespace llvm::object;
 
 namespace llvm {
 namespace sampleprof {
 
+class ProfiledBinary;
+
+struct InstructionPointer {
+  ProfiledBinary *Binary;
+  // Offset to the base address of the executable segment of the binary.
+  uint64_t Offset;
+  // Index to the sorted code address array of the binary.
+  uint64_t Index;
+
+  InstructionPointer(ProfiledBinary *Binary, uint64_t Offset)
+      : Binary(Binary), Offset(Offset) {
+    Index = 0;
+  }
+};
+
 class ProfiledBinary {
   // Absolute path of the binary.
   std::string Path;
   // The target triple.
   Triple TheTriple;
   // The runtime base address that the executable sections are loaded at.
   mutable uint64_t BaseAddress = 0;
   // The preferred base address that the executable sections are loaded at.
class ProfiledBinary {
   // An array of offsets of all instructions sorted in increasing order. The
   // sorting is needed to fast advance to the next forward/backward instruction.
   std::vector<uint64_t> CodeAddrs;
   // A set of call instruction offsets. Used by virtual unwinding.
   std::unordered_set<uint64_t> CallAddrs;
   // A set of return instruction offsets. Used by virtual unwinding.
   std::unordered_set<uint64_t> RetAddrs;
 
+  // The symbolizer used to get inline context for an instruction.
+  std::unique_ptr<symbolize::LLVMSymbolizer> Symbolizer;
+
   void setPreferredBaseAddress(const ELFObjectFileBase *O);
 
   // Set up disassembler and related components.
   void setUpDisassembler(const ELFObjectFileBase *Obj);
+  void setupSymbolizer();
 
   /// Dissassemble the text section and build various address maps.
   void disassemble(const ELFObjectFileBase *O);
 
   /// Helper function to dissassemble the symbol and extract info for unwinding
   bool dissassembleSymbol(std::size_t SI, ArrayRef<uint8_t> Bytes,
                           SectionSymbolsTy &Symbols, const SectionRef &Section);
+  /// Symbolize a given instruction pointer and return a full call context.
+  FrameLocationStack symbolize(const InstructionPointer &I);
 
   /// Decode the interesting parts of the binary and build internal data
   /// structures. On high level, the parts of interest are:
   ///   1. Text sections, including the main code section and the PLT
   ///   entries that will be used to handle cross-module call transitions.
   ///   2. The .debug_line section, used by Dwarf-based profile generation.
   ///   3. Pseudo probe related sections, used by probe-based profile
   ///   generation.
   void load();
 
 public:
-  ProfiledBinary(StringRef Path) : Path(Path) { load(); }
+  ProfiledBinary(StringRef Path) : Path(Path) {
+    setupSymbolizer();
+    load();
+  }
 
   const StringRef getPath() const { return Path; }
   const StringRef getName() const { return llvm::sys::path::filename(Path); }
   uint64_t getBaseAddress() const { return BaseAddress; }
   void setBaseAddress(uint64_t Address) { BaseAddress = Address; }
 };
 
 } // end namespace sampleprof
 } // end namespace llvm
 
 #endif

llvm/tools/llvm-profgen/ProfiledBinary.cpp

 //===-- ProfiledBinary.cpp - Binary decoder ---------------------*- 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 "ProfiledBinary.h"
 #include "ErrorHandling.h"
 #include "MCTargetDesc/X86MCTargetDesc.h"
 #include "llvm/ADT/Triple.h"
 #include "llvm/Demangle/Demangle.h"
 #include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Format.h"
 #include "llvm/Support/TargetRegistry.h"
 #include "llvm/Support/TargetSelect.h"
 #include "llvm/Support/X86TargetParser.h"
 
 #define DEBUG_TYPE "load-binary"
 
 using namespace llvm;
 
 static cl::opt<bool> ShowDisassembly("show-disassembly", cl::ReallyHidden,
                                      cl::init(false), cl::ZeroOrMore,
                                      cl::desc("Print disassembled code."));
 
+static cl::opt<bool> ShowSourceLocations("show-source-locations",
+                                         cl::ReallyHidden, cl::init(false),
+                                         cl::ZeroOrMore,
+                                         cl::desc("Print source locations."));
+
 namespace llvm {
 namespace sampleprof {
 
 static const Target *getTarget(const ObjectFile *Obj) {
   Triple TheTriple = Obj->makeTriple();
   std::string Error;
   std::string ArchName;
   const Target *TheTarget =
while (Offset < EndOffset) {
     uint64_t Size;
     // Disassemble an instruction.
     if (!DisAsm->getInstruction(Inst, Size, Bytes.slice(Offset - SectionOffset),
                                 Offset + PreferredBaseAddress, nulls()))
       return false;
 
     if (ShowDisassembly) {
       outs() << format("%8" PRIx64 ":", Offset);
+      size_t Start = outs().tell();
       IP->printInst(&Inst, Offset + Size, "", *STI.get(), outs());
+      if (ShowSourceLocations) {
+        unsigned Cur = outs().tell() - Start;
+        if (Cur < 40)
+          outs().indent(40 - Cur);
+        InstructionPointer Inst(this, Offset);
+        outs() << getReversedLocWithContext(symbolize(Inst));
+      }
       outs() << "\n";
     }
 
     const MCInstrDesc &MCDesc = MII->get(Inst.getOpcode());
 
     // Populate address maps.
     CodeAddrs.push_back(Offset);
     if (MCDesc.isCall())
for (section_iterator SI = Obj->section_begin(), SE = Obj->section_end();
 
     // Disassemble symbol by symbol.
     for (std::size_t SI = 0, SE = Symbols.size(); SI != SE; ++SI) {
       if (!dissassembleSymbol(SI, Bytes, Symbols, Section))
         exitWithError("disassembling error", FileName);
     }
   }
 }
+
+void ProfiledBinary::setupSymbolizer() {
+  symbolize::LLVMSymbolizer::Options SymbolizerOpts;
+  SymbolizerOpts.PrintFunctions =
+      DILineInfoSpecifier::FunctionNameKind::LinkageName;
+  SymbolizerOpts.Demangle = false;
+  SymbolizerOpts.DefaultArch = TheTriple.getArchName().str();
+  SymbolizerOpts.UseSymbolTable = false;
+  SymbolizerOpts.RelativeAddresses = false;
+  Symbolizer = std::make_unique<symbolize::LLVMSymbolizer>(SymbolizerOpts);
+}
+
+FrameLocationStack ProfiledBinary::symbolize(const InstructionPointer &IP) {
+  assert(this == IP.Binary &&
+         "Binary should only symbolize its own instruction");
+  auto Addr = object::SectionedAddress{IP.Offset + PreferredBaseAddress,
+                                       object::SectionedAddress::UndefSection};
+  DIInliningInfo InlineStack =
+      unwrapOrError(Symbolizer->symbolizeInlinedCode(Path, Addr), getName());
+
+  FrameLocationStack CallStack;
+
+  for (int32_t I = InlineStack.getNumberOfFrames() - 1; I >= 0; I--) {
+    const auto &CallerFrame = InlineStack.getFrame(I);
+    if (CallerFrame.FunctionName == "<invalid>")
+      break;
+    LineLocation Line(CallerFrame.Line - CallerFrame.StartLine,
+                      CallerFrame.Discriminator);
+    FrameLocation Callsite(CallerFrame.FunctionName, Line);
+    CallStack.push_back(Callsite);
+  }
+
+  return CallStack;
+}
+
 } // end namespace sampleprof
 } // end namespace llvm