speeding up simulation using dedicated full dpi-based FPU core

hw/dpi/util_dpi.cpp

@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <math.h>
+#include <unordered_map>
+#include <vector>
+#include <mutex>
+#include <iostream>
+#include "svdpi.h"
+#include "verilated_vpi.h"
+#include "VX_config.h"
+
+extern "C" {
+  int dpi_register();
+  void dpi_assert(int inst, bool cond, int delay);
+}
+
+class ShiftRegister {
+public:
+  ShiftRegister() : init_(false), depth_(0) {}
+
+  void ensure_init(int depth) {
+    if (!init_) {
+      buffer_.resize(depth);
+      init_  = true;
+      depth_ = depth;
+    }
+  }
+
+  void push(int value, bool enable) {
+    if (!enable)
+      return;      
+    for (unsigned i = 0; i < depth_-1; ++i) {
+      buffer_[i] = buffer_[i+1];
+    }
+    buffer_[depth_-1] = value;
+  }
+
+  int top() const {
+    return buffer_[0];
+  }
+
+private:
+
+  std::vector<int> buffer_;
+  bool init_;
+  unsigned depth_;  
+};
+
+class Instances {
+public:
+  ShiftRegister& get(int inst) {
+    return instances_.at(inst);
+  }
+
+  int allocate() {
+    mutex_.lock();   
+    int inst = instances_.size();
+    instances_.resize(inst + 1); 
+    mutex_.unlock();
+    return inst;
+  }
+
+private:
+  std::vector<ShiftRegister> instances_;
+  std::mutex mutex_;
+};
+
+Instances instances;
+
+int dpi_register() {
+  return instances.allocate();
+}
+
+void dpi_assert(int inst, bool cond, int delay) {
+  ShiftRegister& sr = instances.get(inst);
+
+  sr.ensure_init(delay);
+  sr.push(!cond, 1);
+
+  auto status = sr.top();
+  if (status) {
+    printf("delayed assertion at %s!\n", svGetNameFromScope(svGetScope()));
+    std::abort();
+  }
+}