arch: support issuing Atomic Mem Operation (AMO) requests

This patch adds two new functions named amoMemAtomic used in Atomic CPU
model and initiateMemAMO used in Timing CPU models to issue AMO requests
to the memory system.

Change-Id: I962bdc0e5f25b72c170d96ebc136f29a2b230d5e
Reviewed-on: https://gem5-review.googlesource.com/8186
Reviewed-by: Anthony Gutierrez <anthony.gutierrez@amd.com>
Reviewed-by: Jason Lowe-Power <jason@lowepower.com>
Maintainer: Anthony Gutierrez <anthony.gutierrez@amd.com>

src/arch/generic/memhelpers.hh

@@ -121,4 +121,36 @@ writeMemAtomic(XC *xc, Trace::InstRecord *traceData, const MemT &mem,
     return fault;
 }
 
+/// Do atomic read-modify-write (AMO) in atomic mode
+template <class XC, class MemT>
+Fault
+amoMemAtomic(XC *xc, Trace::InstRecord *traceData, MemT &mem, Addr addr,
+             Request::Flags flags, AtomicOpFunctor *amo_op)
+{
+    assert(amo_op);
+
+    // mem will hold the previous value at addr after the AMO completes
+    memset(&mem, 0, sizeof(mem));
+
+    Fault fault = xc->amoMem(addr, (uint8_t *)&mem, sizeof(MemT), flags,
+                             amo_op);
+
+    if (fault == NoFault) {
+        mem = TheISA::gtoh(mem);
+        if (traceData)
+            traceData->setData(mem);
+    }
+    return fault;
+}
+
+/// Do atomic read-modify-wrote (AMO) in timing mode
+template <class XC, class MemT>
+Fault
+initiateMemAMO(XC *xc, Trace::InstRecord *traceData, Addr addr, MemT& mem,
+               Request::Flags flags, AtomicOpFunctor *amo_op)
+{
+    assert(amo_op);
+    return xc->initiateMemAMO(addr, sizeof(MemT), flags, amo_op);
+}
+
 #endif