[BOLT] Fix build for Mac

Summary:
Change our CMake config for the standalone runtime instrumentation
library to check for the elf.h header before using it, so the build
doesn't break on systems lacking it. Also fix a SmallPtrSet usage where
its elements are not really pointers, but uint64_t, breaking the build
in Apple's Clang.

(cherry picked from FBD17505759)

bolt/runtime/CMakeLists.txt

@@ -1,14 +1,24 @@
 cmake_minimum_required(VERSION 3.1.0)
+
+include(CheckIncludeFiles)
+
 set(CMAKE_CXX_STANDARD 11)
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
 
 project(libbolt_rt_project)
 
+check_include_files(elf.h HAVE_ELF_H)
+configure_file(${CMAKE_CURRENT_SOURCE_DIR}/config.h.in
+               ${CMAKE_CURRENT_BINARY_DIR}/config.h)
+
 add_library(bolt_rt STATIC
   instr.cpp
+  ${CMAKE_CURRENT_BINARY_DIR}/config.h
   )
+
 # Don't let the compiler think it can create calls to standard libs
 target_compile_options(bolt_rt PRIVATE -ffreestanding)
+target_include_directories(bolt_rt PRIVATE ${CMAKE_CURRENT_BINARY_DIR})
 
 install(TARGETS bolt_rt DESTINATION lib)

bolt/runtime/config.h.in

@@ -0,0 +1 @@
+#cmakedefine HAVE_ELF_H

bolt/runtime/instr.cpp

@@ -15,7 +15,11 @@
 //===----------------------------------------------------------------------===//
 
 #include <cstdint>
+
+#include "config.h"
+#ifdef HAVE_ELF_H
 #include <elf.h>
+#endif
 
 //#define ENABLE_DEBUG
 
@@ -380,6 +384,7 @@ char *serializeLoc(const InstrumentationInfo &Info, char *OutBuf,
 
 // Read and map to memory the descriptions written by BOLT into the executable's
 // notes section
+#ifdef HAVE_ELF_H
 InstrumentationInfo readDescriptions() {
   InstrumentationInfo Result;
   uint64_t FD = __open("/proc/self/exe",
@@ -431,6 +436,15 @@ InstrumentationInfo readDescriptions() {
   reportError(ErrMsg, sizeof(ErrMsg));
   return Result;
 }
+#else
+InstrumentationInfo readDescriptions() {
+  InstrumentationInfo Result;
+  const char ErrMsg[] =
+    "BOLT instrumentation runtime error: unsupported binary format.\n";
+  reportError(ErrMsg, sizeof(ErrMsg));
+  return Result;
+}
+#endif
 
 void printStats(const InstrumentationInfo &Info) {
   char StatMsg[BufSize];

bolt/src/BinaryFunction.cpp

@@ -16,6 +16,7 @@
 #include "DynoStats.h"
 #include "MCPlusBuilder.h"
 #include "llvm/ADT/edit_distance.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/DebugInfo/DWARF/DWARFContext.h"
 #include "llvm/MC/MCAsmInfo.h"
@@ -3653,7 +3654,7 @@ void BinaryFunction::updateLayout(BinaryBasicBlock *Start,
 }
 
 bool BinaryFunction::checkForAmbiguousJumpTables() {
-  SmallPtrSet<uint64_t, 4> JumpTables;
+  SmallSet<uint64_t, 4> JumpTables;
   for (auto &BB : BasicBlocks) {
     for (auto &Inst : *BB) {
       if (!BC.MIB->isIndirectBranch(Inst))
@@ -3664,8 +3665,7 @@ bool BinaryFunction::checkForAmbiguousJumpTables() {
       // This address can be inside another jump table, but we only consider
       // it ambiguous when the same start address is used, not the same JT
       // object.
-      auto Iter = JumpTables.find(JTAddress);
-      if (Iter == JumpTables.end()) {
+      if (!JumpTables.count(JTAddress)) {
         JumpTables.insert(JTAddress);
         continue;
       }