Revert "[llvm-exegesis] Use LLVM Support to get thread ID"

This reverts commit 1c3b15e.

This (and/or) a related patch was causing build failures on one of the
buildbots. More information is available at
https://lab.llvm.org/buildbot/#/builders/178/builds/7015.

Author: boomanaiden154

llvm/tools/llvm-exegesis/lib/BenchmarkRunner.cpp

@@ -301,7 +301,7 @@ class SubProcessFunctionExecutorImpl
     if (AddMemDefError)
       return AddMemDefError;
 
-    long ParentTID = get_threadid();
+    long ParentTID = SubprocessMemory::getCurrentTID();
     pid_t ParentOrChildPID = fork();
 
     if (ParentOrChildPID == -1) {

llvm/tools/llvm-exegesis/lib/SubprocessMemory.cpp

@@ -10,7 +10,6 @@
 #include "Error.h"
 #include "llvm/Support/Error.h"
 #include "llvm/Support/FormatVariadic.h"
-#include "llvm/Support/Threading.h"
 #include <cerrno>
 
 #ifdef __linux__
@@ -25,14 +24,21 @@ namespace exegesis {
 
 #if defined(__linux__) && !defined(__ANDROID__)
 
+long SubprocessMemory::getCurrentTID() {
+  // We're using the raw syscall here rather than the gettid() function provided
+  // by most libcs for compatibility as gettid() was only added to glibc in
+  // version 2.30.
+  return syscall(SYS_gettid);
+}
+
 Error SubprocessMemory::initializeSubprocessMemory(pid_t ProcessID) {
   // Add the PID to the shared memory name so that if we're running multiple
   // processes at the same time, they won't interfere with each other.
   // This comes up particularly often when running the exegesis tests with
   // llvm-lit. Additionally add the TID so that downstream consumers
   // using multiple threads don't run into conflicts.
   std::string AuxiliaryMemoryName =
-      formatv("/{0}auxmem{1}", get_threadid(), ProcessID);
+      formatv("/{0}auxmem{1}", getCurrentTID(), ProcessID);
   int AuxiliaryMemoryFD = shm_open(AuxiliaryMemoryName.c_str(),
                                    O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
   if (AuxiliaryMemoryFD == -1)
@@ -53,7 +59,7 @@ Error SubprocessMemory::addMemoryDefinition(
   SharedMemoryNames.reserve(MemoryDefinitions.size());
   for (auto &[Name, MemVal] : MemoryDefinitions) {
     std::string SharedMemoryName =
-        formatv("/{0}t{1}memdef{2}", ProcessPID, get_threadid(), MemVal.Index);
+        formatv("/{0}t{1}memdef{2}", ProcessPID, getCurrentTID(), MemVal.Index);
     SharedMemoryNames.push_back(SharedMemoryName);
     int SharedMemoryFD =
         shm_open(SharedMemoryName.c_str(), O_RDWR | O_CREAT, S_IRUSR | S_IWUSR);
@@ -87,7 +93,7 @@ Error SubprocessMemory::addMemoryDefinition(
 
 Expected<int> SubprocessMemory::setupAuxiliaryMemoryInSubprocess(
     std::unordered_map<std::string, MemoryValue> MemoryDefinitions,
-    pid_t ParentPID, uint64_t ParentTID, int CounterFileDescriptor) {
+    pid_t ParentPID, long ParentTID, int CounterFileDescriptor) {
   std::string AuxiliaryMemoryName =
       formatv("/{0}auxmem{1}", ParentTID, ParentPID);
   int AuxiliaryMemoryFileDescriptor =
@@ -139,7 +145,7 @@ Error SubprocessMemory::addMemoryDefinition(
 
 Expected<int> SubprocessMemory::setupAuxiliaryMemoryInSubprocess(
     std::unordered_map<std::string, MemoryValue> MemoryDefinitions,
-    pid_t ParentPID, uint64_t ParentTID, int CounterFileDescriptor) {
+    pid_t ParentPID, long ParentTID, int CounterFileDescriptor) {
   return make_error<Failure>(
       "setupAuxiliaryMemoryInSubprocess is only supported on Linux");
 }

llvm/tools/llvm-exegesis/lib/SubprocessMemory.h

@@ -35,6 +35,9 @@ class SubprocessMemory {
   static constexpr const size_t AuxiliaryMemoryOffset = 1;
   static constexpr const size_t AuxiliaryMemorySize = 4096;
 
+  // Gets the thread ID for the calling thread.
+  static long getCurrentTID();
+
   Error initializeSubprocessMemory(pid_t ProcessID);
 
   // The following function sets up memory definitions. It creates shared
@@ -54,7 +57,7 @@ class SubprocessMemory {
   // section.
   static Expected<int> setupAuxiliaryMemoryInSubprocess(
       std::unordered_map<std::string, MemoryValue> MemoryDefinitions,
-      pid_t ParentPID, uint64_t ParentTID, int CounterFileDescriptor);
+      pid_t ParentPID, long ParentTID, int CounterFileDescriptor);
 
   ~SubprocessMemory();