Avoid memory-allocation anti-pattern on matched_trigger

riscv/execute.cc

@@ -342,10 +342,6 @@ void processor_t::step(size_t n)
     }
     catch (triggers::matched_t& t)
     {
-      if (mmu->matched_trigger) {
-        delete mmu->matched_trigger;
-        mmu->matched_trigger = NULL;
-      }
       take_trigger_action(t.action, t.address, pc, t.gva);
     }
     catch(trap_debug_mode&)

riscv/mmu.cc

@@ -14,8 +14,7 @@ mmu_t::mmu_t(simif_t* sim, endianness_t endianness, processor_t* proc)
 #endif
   check_triggers_fetch(false),
   check_triggers_load(false),
-  check_triggers_store(false),
-  matched_trigger(NULL)
+  check_triggers_store(false)
 {
 #ifndef RISCV_ENABLE_DUAL_ENDIAN
   assert(endianness == endianness_little);
@@ -188,7 +187,7 @@ void mmu_t::check_triggers(triggers::operation_t operation, reg_t address, bool
         // We want to take this exception on the next instruction.  We check
         // whether to do so in the I$ refill path, so flush the I$.
         flush_icache();
-        matched_trigger = new triggers::matched_t(operation, tval, match->action, virt);
+        matched_trigger = triggers::matched_t(operation, tval, match->action, virt);
     }
 }
 

riscv/mmu.h

@@ -293,8 +293,11 @@ public:
 
   inline icache_entry_t* refill_icache(reg_t addr, icache_entry_t* entry)
   {
-    if (matched_trigger)
-      throw *matched_trigger;
+    if (matched_trigger) {
+      auto trig = matched_trigger.value();
+      matched_trigger.reset();
+      throw trig;
+    }
 
     auto [first_parcel, paddr] = fetch_insn_parcel_and_paddr(addr);
     insn_bits_t insn = first_parcel;
@@ -507,8 +510,7 @@ private:
   bool check_triggers_fetch;
   bool check_triggers_load;
   bool check_triggers_store;
-  // The exception describing a matched trigger, or NULL.
-  triggers::matched_t *matched_trigger;
+  std::optional<triggers::matched_t> matched_trigger;
 
   friend class processor_t;
 };