fastmodel: delay the breakpoint event handle to simulation stop

The fastmodel simulation would be paused when it hits a breakpoint.
However, the order of stop event happens after the breakpoint event. If
we handle the breakpoint logic in the breakpoint event, it may cause
somehow status unsynchronized. To make the behavior stable, we delay the
breakpoint handle until the simulation stop event called.

Change-Id: I0083561f561af71370ccaa066220b72ed7831b78
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/68697
Reviewed-by: Earl Ou <shunhsingou@google.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/arch/arm/fastmodel/iris/thread_context.cc

@@ -269,6 +269,22 @@ ThreadContext::simulationTimeEvent(
         return iris::E_ok;
     }
 
+    // Handle the breakpoint event at simulation is stopped if needed.
+    if (bpAddr.has_value()) {
+        auto it = getOrAllocBp(bpAddr.value());
+
+        std::shared_ptr<BpInfo::EventList> events = it->second->events;
+        auto e_it = events->begin();
+        while (e_it != events->end()) {
+            PCEvent *e = *e_it;
+            // Advance e_it here since e might remove itself from the list.
+            e_it++;
+            e->process(this);
+        }
+
+        bpAddr.reset();
+    }
+
     // If simulation time has stopped for any reason, IRIS helpfully clears
     // all stepping counters and we need to set them back. We might also need
     // to service events based on the current number of executed instructions.
@@ -286,19 +302,10 @@ ThreadContext::breakpointHit(
         uint64_t esId, const iris::IrisValueMap &fields, uint64_t time,
         uint64_t sInstId, bool syncEc, std::string &error_message_out)
 {
+    // Handle the breakpoint event later when the fastmodel simulation is
+    // stopped.
     Addr pc = fields.at("PC").getU64();
-
-    auto it = getOrAllocBp(pc);
-
-    std::shared_ptr<BpInfo::EventList> events = it->second->events;
-    auto e_it = events->begin();
-    while (e_it != events->end()) {
-        PCEvent *e = *e_it;
-        // Advance e_it here since e might remove itself from the list.
-        e_it++;
-        e->process(this);
-    }
-
+    bpAddr = pc;
     return iris::E_ok;
 }
 

src/arch/arm/fastmodel/iris/thread_context.hh

@@ -31,6 +31,7 @@
 #include <list>
 #include <map>
 #include <memory>
+#include <optional>
 #include <unordered_map>
 
 #include "arch/arm/fastmodel/iris/memory_spaces.hh"
@@ -133,6 +134,7 @@ class ThreadContext : public gem5::ThreadContext
     using BpInfoIt = BpInfoMap::iterator;
 
     BpInfoMap bps;
+    std::optional<Addr> bpAddr;
 
     BpInfoIt getOrAllocBp(Addr pc);