Set PERF_IOC_FLAG_GROUP on ioctl calls

Without this call, the ioctl calls only work by chance and fail in
certain cases, like when the users sets the RDX register in subprocess
mode.

Author: boomanaiden154

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

@@ -154,12 +154,12 @@ Counter::~Counter() {
 
 void Counter::start() {
   if (!IsDummyEvent)
-    ioctl(FileDescriptor, PERF_EVENT_IOC_RESET, 0);
+    ioctl(FileDescriptor, PERF_EVENT_IOC_RESET, PERF_IOC_FLAG_GROUP);
 }
 
 void Counter::stop() {
   if (!IsDummyEvent)
-    ioctl(FileDescriptor, PERF_EVENT_IOC_DISABLE, 0);
+    ioctl(FileDescriptor, PERF_EVENT_IOC_DISABLE, PERF_IOC_FLAG_GROUP);
 }
 
 llvm::Expected<llvm::SmallVector<int64_t, 4>>

llvm/tools/llvm-exegesis/lib/X86/Target.cpp

@@ -45,6 +45,9 @@
 #include <sys/mman.h>
 #include <sys/syscall.h>
 #include <unistd.h>
+#ifdef HAVE_LIBPFM
+#include <perfmon/perf_event.h>
+#endif // HAVE_LIBPFM
 #endif
 
 #define GET_AVAILABLE_OPCODE_CHECKER
@@ -1252,7 +1255,7 @@ std::vector<MCInst>
 ExegesisX86Target::configurePerfCounter(long Request, bool SaveRegisters) const {
   std::vector<MCInst> ConfigurePerfCounterCode;
   if (SaveRegisters)
-    saveSyscallRegisters(ConfigurePerfCounterCode, 2);
+    saveSyscallRegisters(ConfigurePerfCounterCode, 3);
   ConfigurePerfCounterCode.push_back(
       loadImmediate(X86::RDI, 64, APInt(64, getAuxiliaryMemoryStartAddress())));
   ConfigurePerfCounterCode.push_back(MCInstBuilder(X86::MOV32rm)
@@ -1264,9 +1267,13 @@ ExegesisX86Target::configurePerfCounter(long Request, bool SaveRegisters) const
                                          .addReg(0));
   ConfigurePerfCounterCode.push_back(
       loadImmediate(X86::RSI, 64, APInt(64, Request)));
+#ifdef HAVE_LIBPFM
+  ConfigurePerfCounterCode.push_back(
+      loadImmediate(X86::RDX, 64, APInt(64, PERF_IOC_FLAG_GROUP)));
+#endif // HAVE_LIBPFM
   generateSyscall(SYS_ioctl, ConfigurePerfCounterCode);
   if (SaveRegisters)
-    restoreSyscallRegisters(ConfigurePerfCounterCode, 2);
+    restoreSyscallRegisters(ConfigurePerfCounterCode, 3);
   return ConfigurePerfCounterCode;
 }