From c72951a36d6cb9775dc1ecd9bc26bc13e796f10c Mon Sep 17 00:00:00 2001
From: Julian Blake Kongslie
Date: Sat, 2 Jul 2022 13:45:09 -0700
Subject: Dropping the async interface, and adding some real uarch.

---
 sim/sim.cpp | 83 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 83 insertions(+)
 create mode 100644 sim/sim.cpp

(limited to 'sim/sim.cpp')

diff --git a/sim/sim.cpp b/sim/sim.cpp
new file mode 100644
index 0000000..e8f84ee
--- /dev/null
+++ b/sim/sim.cpp
@@ -0,0 +1,83 @@
+#include <utility>
+
+#include "sim/sim.h"
+#include "util/assert.h"
+
+namespace sim {
+
+    void Scheduler::add_schedulable(Schedulable *schedulable)
+    {
+        unsorted_schedulables.emplace(schedulable);
+        sort_needed = true;
+    }
+
+    void Scheduler::remove_schedulable(Schedulable *schedulable)
+    {
+        unsorted_schedulables.erase(schedulable);
+        std::erase_if(constraints, [schedulable](const auto &item) { return item.first == schedulable || item.second == schedulable; });
+        sort_needed = true;
+    }
+
+    void Scheduler::constrain(Schedulable *prior, Schedulable *later)
+    {
+        ASSERT(unsorted_schedulables.count(prior), "Constraint prior is not associated with this Scheduler");
+        ASSERT(unsorted_schedulables.count(later), "Constraint later is not associated with this Scheduler");
+        constraints.emplace(later, prior);
+        sort_needed = true;
+    }
+
+    void Scheduler::topo_sort(std::set<Schedulable *> &live, std::set<Schedulable *> &waiting, Schedulable *candidate)
+    {
+        ASSERT(!live.count(candidate), "Dependency loop");
+        for (auto prereq = constraints.find(candidate); prereq != constraints.end() && prereq->first == candidate; ++prereq) {
+            if (prereq->second != candidate && waiting.count(prereq->second)) {
+                live.emplace(candidate);
+                topo_sort(live, waiting, prereq->second);
+            }
+        }
+        sorted_schedulables.emplace_back(candidate);
+        waiting.erase(candidate);
+    }
+
+    void Scheduler::sort()
+    {
+        sorted_schedulables.clear();
+        sorted_schedulables.reserve(unsorted_schedulables.size());
+        auto waiting = unsorted_schedulables;
+        while (!waiting.empty()) {
+            std::set<Schedulable *> live;
+            topo_sort(live, waiting, *waiting.begin());
+        }
+        ASSERT(sorted_schedulables.size() == unsorted_schedulables.size(), "Did not sort every schedulable");
+        sort_needed = false;
+    }
+
+    void Scheduler::clock()
+    {
+        if (sort_needed)
+            sort();
+        for (const auto &s : sorted_schedulables) {
+            current_schedulable = s;
+            s->clock();
+        }
+        current_schedulable = nullptr;
+        ++now;
+    }
+
+    Schedulable::Schedulable(Scheduler &scheduler)
+        : scheduler(scheduler)
+    {
+        scheduler.add_schedulable(this);
+    }
+
+    Schedulable::~Schedulable()
+    {
+        scheduler.remove_schedulable(this);
+    }
+
+    std::uint64_t Schedulable::now()
+    {
+        return scheduler.now;
+    }
+
+}
-- 
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