write DCE

include/IR/IR_basic.h

@@ -64,7 +64,11 @@ class GlobalVarDefItem : public LLVMIRItemBase {
     }
   }
 };
-class ActionItem : public LLVMIRItemBase {};
+class ActionItem : public LLVMIRItemBase {
+ public:
+  bool marked_as_useless;
+  ActionItem() : marked_as_useless(false) {}
+};
 class JMPActionItem : public ActionItem {
  public:
   std::shared_ptr<class PhiItem> corresponding_phi;

include/opt/dce.h

@@ -0,0 +1,4 @@
+#pragma once
+#include "IR/IR_basic.h"
+
+std::shared_ptr<ModuleItem> DCE(std::shared_ptr<ModuleItem> src);

include/opt/opt.h

@@ -3,3 +3,4 @@
 #include "global_var_cache.h"
 #include "mem2reg.h"
 #include "regalloc.h"
+#include "dce.h"

src/main.cpp

@@ -49,6 +49,7 @@ int main(int argc, char **argv) {
       auto IR_with_out_allocas = Mem2Reg(IR);
       // IR_with_out_allocas->RecursivePrint(std::cerr);
       IR_with_out_allocas = GloabalVarCache(IR_with_out_allocas);
+      IR_with_out_allocas = DCE(IR_with_out_allocas);
       // IR_with_out_allocas->RecursivePrint(std::cerr);
       auto IR_with_out_phis = PhiEliminate(IR_with_out_allocas);
       // IR_with_out_phis->RecursivePrint(std::cerr);

src/opt/dce.cpp

@@ -0,0 +1,63 @@
+#include "dce.h"
+#include "IR/IR_basic.h"
+#include "cfg.h"
+#include "liveanalysis.h"
+void ConductDCEForFunction(std::shared_ptr<FunctionDefItem> func);
+
+void ConductDCEForFunction(std::shared_ptr<FunctionDefItem> func) {
+  CFGType cfg;
+  cfg = BuildCFGForFunction(func);
+  LiveAnalysis(cfg);
+  std::unordered_set<std::string> all_vars;
+  std::unordered_map<std::string, std::unordered_set<ActionItem *>> use_map, def_map;
+  std::unordered_map<ActionItem *, std::vector<size_t>> actions_use_vars;
+  for (size_t i = 0; i < cfg.id_to_var.size(); i++) {
+    all_vars.insert(cfg.id_to_var[i]);
+  }
+  for (auto node : cfg.nodes) {
+    for (const auto &[action, use_vars] : node->action_use_vars) {
+      for (auto var_id : use_vars) {
+        use_map[cfg.id_to_var[var_id]].insert(action);
+      }
+      actions_use_vars[action] = use_vars;
+    }
+    for (const auto &[action, def_vars] : node->action_def_vars) {
+      for (auto var_id : def_vars) {
+        def_map[cfg.id_to_var[var_id]].insert(action);
+      }
+    }
+  }
+  while (all_vars.size() > 0) {
+    auto v = *(all_vars.begin());
+    all_vars.erase(v);
+    if (use_map[v].size() == 0) {
+      if (def_map[v].size() != 1) throw std::runtime_error("def_map[v].size()!=1");
+      auto def_inst = *(def_map[v].begin());
+      if (!dynamic_cast<CallItem *>(def_inst)) {
+        // no side effect
+        def_inst->marked_as_useless = true;
+        const auto &use_vars = actions_use_vars[def_inst];
+        for (auto var_id : use_vars) {
+          use_map[cfg.id_to_var[var_id]].erase(def_inst);
+          all_vars.insert(cfg.id_to_var[var_id]);
+        }
+      }
+    }
+  }
+  for (auto node : cfg.nodes) {
+    auto block = node->corresponding_block;
+    auto tmp = block->actions;
+    block->actions.clear();
+    for (auto act : tmp) {
+      if (!act->marked_as_useless) {
+        block->actions.push_back(act);
+      }
+    }
+  }
+}
+std::shared_ptr<ModuleItem> DCE(std::shared_ptr<ModuleItem> src) {
+  for (auto func : src->function_defs) {
+    ConductDCEForFunction(func);
+  }
+  return src;
+}

src/opt/liveanalysis.cpp

@@ -22,6 +22,9 @@ void VarCollect(CFGType &cfg, std::vector<std::string> &id_to_var, std::unordere
   };
   for (auto node : cfg.nodes) {
     auto block = node->corresponding_block;
+    for (auto [_, phi_act] : block->phi_map) {
+      TryAddVar(phi_act->result_full);
+    }
     for (auto act : block->actions) {
       if (auto bin_act = std::dynamic_pointer_cast<BinaryOperationAction>(act)) {
         TryAddVar(bin_act->result_full);
@@ -46,6 +49,8 @@ void VarCollect(CFGType &cfg, std::vector<std::string> &id_to_var, std::unordere
         TryAddVar(load_spilled_args_act->var_full);
       } else if (auto alloca_act = std::dynamic_pointer_cast<AllocaAction>(act)) {
         TryAddVar(alloca_act->name_full);
+      } else if (auto phi_act = std::dynamic_pointer_cast<PhiItem>(act)) {
+        TryAddVar(phi_act->result_full);
       }
     }
   }
@@ -63,6 +68,47 @@ void UseDefCollect(CFGType &cfg, [[maybe_unused]] std::vector<std::string> &id_t
     std::vector<size_t> cur_node_use;
     std::vector<size_t> cur_node_def;
     bool use_def_init = false;
+    for (auto [_, phi_act] : block->phi_map) {
+      std::vector<size_t> &cur_act_use = node->action_use_vars[phi_act.get()];
+      std::vector<size_t> &cur_act_def = node->action_def_vars[phi_act.get()];
+      if (var_to_id.find(phi_act->result_full) != var_to_id.end()) {
+        cur_act_def.push_back(var_to_id[phi_act->result_full]);
+      }
+      std::unordered_set<size_t> cur_act_use_tmp;
+      for (auto &[value, _] : phi_act->values) {
+        if (var_to_id.find(value) != var_to_id.end()) {
+          // cur_act_use.push_back(var_to_id[value]);
+          cur_act_use_tmp.insert(var_to_id[value]);
+        }
+      }
+      for (size_t i : cur_act_use_tmp) {
+        cur_act_use.push_back(i);
+      }
+      std::sort(cur_act_use.begin(), cur_act_use.end());
+      std::sort(cur_act_def.begin(), cur_act_def.end());
+      for (size_t i = 1; i < cur_act_use.size(); i++) {
+        if (cur_act_use[i] == cur_act_use[i - 1]) {
+          throw std::runtime_error("use variable appears twice in one action");
+        }
+      }
+      for (size_t i = 1; i < cur_act_def.size(); i++) {
+        if (cur_act_def[i] == cur_act_def[i - 1]) {
+          throw std::runtime_error("def variable appears twice in one action");
+        }
+      }
+      if (!use_def_init) {
+        use_def_init = true;
+        cur_node_use = cur_act_use;
+        cur_node_def = cur_act_def;
+      } else {
+        const auto &use_p = cur_node_use;
+        const auto &def_p = cur_node_def;
+        const auto &use_n = cur_act_use;
+        const auto &def_n = cur_act_def;
+        cur_node_use = GetCollectionsUnion(use_p, GetCollectionsDifference(use_n, def_p));
+        cur_node_def = GetCollectionsUnion(def_p, def_n);
+      }
+    }
     for (auto act : block->actions) {
       std::vector<size_t> &cur_act_use = node->action_use_vars[act.get()];
       std::vector<size_t> &cur_act_def = node->action_def_vars[act.get()];
@@ -182,6 +228,20 @@ void UseDefCollect(CFGType &cfg, [[maybe_unused]] std::vector<std::string> &id_t
         }
       } else if (auto alloca_act = std::dynamic_pointer_cast<AllocaAction>(act)) {
         cur_act_def.push_back(var_to_id[alloca_act->name_full]);
+      } else if (auto phi_act = std::dynamic_pointer_cast<PhiItem>(act)) {
+        if (var_to_id.find(phi_act->result_full) != var_to_id.end()) {
+          cur_act_def.push_back(var_to_id[phi_act->result_full]);
+        }
+        std::unordered_set<size_t> cur_act_use_tmp;
+        for (auto &[value, _] : phi_act->values) {
+          if (var_to_id.find(value) != var_to_id.end()) {
+            // cur_act_use.push_back(var_to_id[value]);
+            cur_act_use_tmp.insert(var_to_id[value]);
+          }
+        }
+        for (size_t i : cur_act_use_tmp) {
+          cur_act_use.push_back(i);
+        }
       }
       std::sort(cur_act_use.begin(), cur_act_use.end());
       std::sort(cur_act_def.begin(), cur_act_def.end());