sim: Remove _numContexts member in System class

A System object has a _numContexts member variable which represent the
number of ThreadContext registered in the System.  Since this has to
match the size of the ThreadContext vector, this patch removes the
manually cached size. This was usually used as a for-loop index, whereas
we want to enforce the use of range-based loops whenever possible.

Change-Id: I1ba317c0393bcc9c1aeebbb1fc22d7b2bc2cf90c
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/8062
Reviewed-by: Gabe Black <gabeblack@google.com>
Maintainer: Brandon Potter <Brandon.Potter@amd.com>

src/arch/arm/kvm/gic.cc

@@ -305,7 +305,7 @@ void
 MuxingKvmGic::copyBankedDistRange(BaseGicRegisters* from, BaseGicRegisters* to,
                                   Addr daddr, size_t size)
 {
-    for (int ctx = 0; ctx < system._numContexts; ++ctx)
+    for (int ctx = 0; ctx < system.numContexts(); ++ctx)
         for (auto a = daddr; a < daddr + size; a += 4)
             copyDistRegister(from, to, ctx, a);
 }
@@ -314,7 +314,7 @@ void
 MuxingKvmGic::clearBankedDistRange(BaseGicRegisters* to,
                                    Addr daddr, size_t size)
 {
-    for (int ctx = 0; ctx < system._numContexts; ++ctx)
+    for (int ctx = 0; ctx < system.numContexts(); ++ctx)
         for (auto a = daddr; a < daddr + size; a += 4)
             to->writeDistributor(ctx, a, 0xFFFFFFFF);
 }
@@ -345,7 +345,7 @@ MuxingKvmGic::copyGicState(BaseGicRegisters* from, BaseGicRegisters* to)
     // Copy CPU Interface Control Register (CTLR),
     //      Interrupt Priority Mask Register (PMR), and
     //      Binary Point Register (BPR)
-    for (int ctx = 0; ctx < system._numContexts; ++ctx) {
+    for (int ctx = 0; ctx < system.numContexts(); ++ctx) {
         copyCpuRegister(from, to, ctx, GICC_CTLR);
         copyCpuRegister(from, to, ctx, GICC_PMR);
         copyCpuRegister(from, to, ctx, GICC_BPR);
@@ -423,7 +423,7 @@ MuxingKvmGic::fromKvmToPl390()
     // have been shifted by three bits due to its having been emulated by
     // a VGIC with only 5 PMR bits in its VMCR register.  Presently the
     // Linux kernel does not repair this inaccuracy, so we correct it here.
-    for (int cpu = 0; cpu < system._numContexts; ++cpu) {
+    for (int cpu = 0; cpu < system.numContexts(); ++cpu) {
        cpuPriority[cpu] <<= 3;
        assert((cpuPriority[cpu] & ~0xff) == 0);
     }

src/arch/arm/linux/system.cc

@@ -250,8 +250,7 @@ LinuxArmSystem::startup()
         std::string task_filename = "tasks.txt";
         taskFile = simout.create(name() + "." + task_filename);
 
-        for (int i = 0; i < _numContexts; i++) {
-            ThreadContext *tc = threadContexts[i];
+        for (const auto tc : threadContexts) {
             uint32_t pid = tc->getCpuPtr()->getPid();
             if (pid != BaseCPU::invldPid) {
                 mapPid(tc, pid);

src/sim/system.cc

@@ -47,6 +47,8 @@
 
 #include "sim/system.hh"
 
+#include <algorithm>
+
 #include "arch/remote_gdb.hh"
 #include "arch/utility.hh"
 #include "base/loader/object_file.hh"
@@ -87,7 +89,6 @@ int System::numSystemsRunning = 0;
 
 System::System(Params *p)
     : MemObject(p), _systemPort("system_port", this),
-      _numContexts(0),
       multiThread(p->multi_thread),
       pagePtr(0),
       init_param(p->init_param),
@@ -256,7 +257,6 @@ System::registerThreadContext(ThreadContext *tc, ContextID assigned)
              "Cannot have two CPUs with the same id (%d)\n", id);
 
     threadContexts[id] = tc;
-    _numContexts++;
 
 #if THE_ISA != NULL_ISA
     int port = getRemoteGDBPort();
@@ -287,12 +287,13 @@ System::registerThreadContext(ThreadContext *tc, ContextID assigned)
 int
 System::numRunningContexts()
 {
-    int running = 0;
-    for (int i = 0; i < _numContexts; ++i) {
-        if (threadContexts[i]->status() != ThreadContext::Halted)
-            ++running;
-    }
-    return running;
+    return std::count_if(
+        threadContexts.cbegin(),
+        threadContexts.cend(),
+        [] (ThreadContext* tc) {
+            return tc->status() != ThreadContext::Halted;
+        }
+    );
 }
 
 void

src/sim/system.hh

@@ -196,7 +196,6 @@ class System : public MemObject
 #endif
 
     std::vector<ThreadContext *> threadContexts;
-    int _numContexts;
     const bool multiThread;
 
     ThreadContext *getThreadContext(ContextID tid)
@@ -204,11 +203,7 @@ class System : public MemObject
         return threadContexts[tid];
     }
 
-    int numContexts()
-    {
-        assert(_numContexts == (int)threadContexts.size());
-        return _numContexts;
-    }
+    unsigned numContexts() const { return threadContexts.size(); }
 
     /** Return number of running (non-halted) thread contexts in
      * system.  These threads could be Active or Suspended. */