misc: Fix mismatched struct/class "tags" and reenable that warning.

The mismatches were from places where Params structs had been declared
as classes instead of structs, and ruby's MachineID struct.

A comment describing why the warning had been disabled said that it was
because of libstdc++ version 4.8. As far as I can tell, that version is
old enough to be outside the window we support, and so that should no
longer be a problem. It looks like the oldest version of gcc we
support, 5.0, corresponds with approximately libstdc++ version 6.0.21.

https://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html#abi.versioning

Change-Id: I75ad92f3723a1883bd47e3919c5572a353344047
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/40953
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

SConstruct

@@ -387,13 +387,7 @@ elif main['CLANG']:
     # parantheses are allowed due to Ruby's printing of the AST,
     # finally self assignments are allowed as the generated CPU code
     # is relying on this
-    main.Append(CCFLAGS=['-Wno-parentheses',
-                         '-Wno-self-assign',
-                         # Some versions of libstdc++ (4.8?) seem to
-                         # use struct hash and class hash
-                         # interchangeably.
-                         '-Wno-mismatched-tags',
-                         ])
+    main.Append(CCFLAGS=['-Wno-parentheses', '-Wno-self-assign'])
     conf.CheckCxxFlag('-Wno-c99-designator')
     conf.CheckCxxFlag('-Wno-defaulted-function-deleted')
 

src/arch/arm/pmu.hh

@@ -52,7 +52,7 @@
 #include "sim/sim_object.hh"
 #include "sim/system.hh"
 
-class ArmPMUParams;
+struct ArmPMUParams;
 class Platform;
 class ThreadContext;
 class ArmInterruptPin;

src/dev/arm/css/mhu.hh

@@ -41,12 +41,12 @@
 #include "dev/arm/doorbell.hh"
 #include "dev/io_device.hh"
 
-class Ap2ScpDoorbellParams;
+struct Ap2ScpDoorbellParams;
 class ArmInterruptPin;
 class MHU;
-class MHUParams;
+struct MHUParams;
 class Scp;
-class Scp2ApDoorbellParams;
+struct Scp2ApDoorbellParams;
 
 class MhuDoorbell : public Doorbell
 {

src/dev/arm/display.hh

@@ -40,7 +40,7 @@
 
 #include "sim/sim_object.hh"
 
-class DisplayParams;
+struct DisplayParams;
 
 class Display : public SimObject
 {

src/dev/arm/fvp_base_pwr_ctrl.hh

@@ -44,7 +44,7 @@
 #include "dev/io_device.hh"
 
 class ArmSystem;
-class FVPBasePwrCtrlParams;
+struct FVPBasePwrCtrlParams;
 class ThreadContext;
 
 /**

src/dev/arm/generic_timer.hh

@@ -64,10 +64,10 @@
 ///     I2 - System Level Implementation of the Generic Timer
 
 class Checkpoint;
-class SystemCounterParams;
-class GenericTimerParams;
-class GenericTimerFrameParams;
-class GenericTimerMemParams;
+struct SystemCounterParams;
+struct GenericTimerParams;
+struct GenericTimerFrameParams;
+struct GenericTimerMemParams;
 
 /// Abstract class for elements whose events depend on the counting speed
 /// of the System Counter

src/dev/arm/gpu_nomali.hh

@@ -43,8 +43,8 @@
 #include "dev/io_device.hh"
 #include "libnomali/nomali.h"
 
-class NoMaliGpuParams;
-class CustomNoMaliGpuParams;
+struct NoMaliGpuParams;
+struct CustomNoMaliGpuParams;
 class RealView;
 
 class NoMaliGpu : public PioDevice

src/dev/arm/watchdog_generic.hh

@@ -42,7 +42,7 @@
 #include "dev/io_device.hh"
 
 class ArmInterruptPin;
-class GenericWatchdogParams;
+struct GenericWatchdogParams;
 
 /**
  * @file

src/dev/arm/watchdog_sp805.hh

@@ -40,7 +40,7 @@
 
 #include "dev/arm/amba_device.hh"
 
-class Sp805Params;
+struct Sp805Params;
 
 /**
  * @file

src/gpu-compute/scheduler.hh

@@ -38,7 +38,7 @@
 
 #include "gpu-compute/scheduling_policy.hh"
 
-class ComputeUnitParams;
+struct ComputeUnitParams;
 
 class Scheduler
 {

src/mem/qos/mem_sink.hh

@@ -46,7 +46,7 @@
 #include "mem/qport.hh"
 #include "params/QoSMemSinkCtrl.hh"
 
-class QoSMemSinkInterfaceParams;
+struct QoSMemSinkInterfaceParams;
 class QoSMemSinkInterface;
 
 namespace QoS {

src/mem/ruby/system/GPUCoalescer.hh

@@ -52,10 +52,10 @@
 
 class DataBlock;
 class CacheMsg;
-class MachineID;
+struct MachineID;
 class CacheMemory;
 
-class RubyGPUCoalescerParams;
+struct RubyGPUCoalescerParams;
 
 // List of packets that belongs to a specific instruction.
 typedef std::list<PacketPtr> PerInstPackets;

src/mem/ruby/system/VIPERCoalescer.hh

@@ -46,10 +46,10 @@
 
 class DataBlock;
 class CacheMsg;
-class MachineID;
+struct MachineID;
 class CacheMemory;
 
-class VIPERCoalescerParams;
+struct VIPERCoalescerParams;
 
 class VIPERCoalescer : public GPUCoalescer
 {

src/sim/mem_state.hh

@@ -42,7 +42,7 @@
 #include "sim/vma.hh"
 
 class Process;
-class ProcessParams;
+struct ProcessParams;
 class System;
 
 /**

src/sim/probe/probe.hh

@@ -69,7 +69,7 @@
 /** Forward declare the ProbeManager. */
 class ProbeManager;
 class ProbeListener;
-class ProbeListenerObjectParams;
+struct ProbeListenerObjectParams;
 
 /**
  * Name space containing shared probe point declarations.

src/sim/ticked_object.hh

@@ -48,7 +48,7 @@
 
 #include "sim/clocked_object.hh"
 
-class TickedObjectParams;
+struct TickedObjectParams;
 
 /** Ticked attaches gem5's event queue/scheduler to evaluate
  *  calls and provides a start/stop interface to ticking.