[syntax tree] trivial phi-node elimination

include/codegen/lowering.h

@@ -139,8 +139,8 @@ Value* llvm_value(ir::value *v, LLVMContext &ctx,
     return vmap.at(v);
   // create operands
   if(auto *uu = dynamic_cast<ir::user*>(v))
-  for(ir::use u: uu->ops()){
-    vmap[u.get()] = llvm_value(u, ctx, vmap, bmap);
+  for(ir::value* u: uu->ops()){
+    vmap[u] = llvm_value(u, ctx, vmap, bmap);
   }
   if(auto *cc = dynamic_cast<ir::constant*>(v))
     return llvm_constant(cc, ctx);

include/ir/basic_block.h

@@ -36,6 +36,7 @@ public:
 
   // get instruction list
   inst_list_t           &get_inst_list()       { return inst_list_; }
+  void  erase(instruction *i)                  {  inst_list_.remove(i); }
 
   // instruction iterator functions
   inline iterator                begin()       { return inst_list_.begin(); }

include/ir/instructions.h

@@ -21,11 +21,11 @@ protected:
   instruction(type *ty, unsigned num_ops, const std::string &name = "", instruction *next = nullptr);
 
 public:
-
   // parent
   void set_parent(basic_block *block)   { parent_ = block; }
   const basic_block *get_parent() const { return parent_;  }
   basic_block *get_parent()             { return parent_;  }
+  void erase_from_parent();
 
 private:
   basic_block *parent_;

include/ir/value.h

@@ -4,6 +4,7 @@
 #include <string>
 #include <vector>
 #include <memory>
+#include <set>
 
 namespace tdl{
 namespace ir{
@@ -22,8 +23,9 @@ public:
   value(type *ty, const std::string &name = "");
   virtual ~value(){ }
   // uses
-  void add_use(use arg);
-  const std::vector<use> &get_uses() { return uses_; }
+  void add_use(user* arg);
+  unsigned erase_use(user* arg);
+  const std::set<user*> &get_users() { return users_; }
   virtual void replace_all_uses_with(value *target);
   // name
   void set_name(const std::string &name);
@@ -35,27 +37,7 @@ private:
   std::string name_;
 
 protected:
-  std::vector<use> uses_;
-};
-
-//===----------------------------------------------------------------------===//
-//                               use class
-//===----------------------------------------------------------------------===//
-
-class use {
-public:
-  // Implicit conversions to/from value
-  friend class value;
-  operator value *() const { return val_; }
-  value *get() const { return val_; }
-  value *operator->() { return val_; }
-  const value *operator->() const { return val_; }
-  inline void set(value *val);
-  inline value *operator=(value *rhs);
-  inline const use &operator=(const use &rhs);
-
-private:
-  value *val_;
+  std::set<user*> users_;
 };
 
 //===----------------------------------------------------------------------===//
@@ -64,7 +46,7 @@ private:
 
 class user: public value{
 public:
-  typedef std::vector<use>      ops_t;
+  typedef std::vector<value*>      ops_t;
   typedef ops_t::iterator       op_iterator;
   typedef ops_t::const_iterator const_op_iterator;
 
@@ -77,7 +59,7 @@ public:
       : value(ty, name), ops_(num_ops){ }
 
   // Operands
-  const std::vector<use>& ops() { return ops_; }
+  const ops_t& ops() { return ops_; }
   op_iterator op_begin() { return ops_.begin(); }
   op_iterator op_end()   { return ops_.end(); }
   void     set_operand(unsigned i, value *x);
@@ -89,7 +71,7 @@ public:
   void replace_uses_of_with(value *before, value *after);
 
 private:
-  std::vector<use> ops_;
+  ops_t ops_;
 };
 
 }

lib/ir/basic_block.cpp

@@ -23,6 +23,8 @@ void basic_block::add_predecessor(basic_block *pred) {
   preds_.push_back(pred);
 }
 
+
+
 basic_block::iterator basic_block::get_first_non_phi(){
   auto it = begin();
   for(; it != end(); it++)

lib/ir/instructions.cpp

@@ -21,6 +21,11 @@ instruction::instruction(type *ty, unsigned num_ops, const std::string &name, in
   }
 }
 
+void instruction::erase_from_parent() {
+  parent_->erase(this);
+}
+
+
 //===----------------------------------------------------------------------===//
 //                               phi_node classes
 //===----------------------------------------------------------------------===//

lib/ir/module.cpp

@@ -40,23 +40,22 @@ ir::phi_node* module::make_phi(ir::type *ty, unsigned num_values, ir::basic_bloc
 }
 
 ir::value *module::try_remove_trivial_phis(ir::phi_node *&phi){
-  ir::value *same = nullptr;
-  for(ir::value *op: phi->ops()){
-    // unique value or self-reference
-    if(op == same || op == phi)
-      continue;
-    // the phi-node merges at least two values; non-trivial
-    if(same)
-      return phi;
-    same = op;
-  }
-  assert(same && "the phi-node is unreachable or in the start block");
-  std::vector<ir::use> uses = phi->get_uses();
+  // find non-self references
+  std::vector<ir::value*> non_self_ref;
+  std::copy_if(phi->ops().begin(), phi->ops().end(), std::back_inserter(non_self_ref),
+               [phi](ir::value* op){ return  op != phi; });
+  // non-trivial
+  if(non_self_ref.size() > 1)
+    return phi;
+  // unique value or self-reference
+  ir::value *same = non_self_ref[0];
+  std::set<ir::user*> users = phi->get_users();
   phi->replace_all_uses_with(same);
-  for(ir::use &u: uses)
-  if(auto *uphi = dynamic_cast<ir::phi_node*>(u.get()))
-  if(uphi != phi)
-    try_remove_trivial_phis(uphi);
+  phi->erase_from_parent();
+  for(ir::user* u: users)
+  if(auto *uphi = dynamic_cast<ir::phi_node*>(u))
+    if(uphi != phi)
+      try_remove_trivial_phis(uphi);
   return same;
 }
 

lib/ir/value.cpp

@@ -1,4 +1,5 @@
 #include "ir/value.h"
+#include "ir/instructions.h"
 #include <iostream>
 #include <cassert>
 
@@ -15,8 +16,12 @@ value::value(type *ty, const std::string &name): ty_(ty){
   set_name(name);
 }
 
-void value::add_use(use arg) {
-  uses_.push_back(arg);
+void value::add_use(user *arg) {
+  users_.insert(arg);
+}
+
+unsigned value::erase_use(user *arg){
+  return users_.erase(arg);
 }
 
 // TODO: automatic naming scheme + update symbol table
@@ -29,30 +34,13 @@ void value::replace_all_uses_with(value *target){
 }
 
 
-//===----------------------------------------------------------------------===//
-//                               use class
-//===----------------------------------------------------------------------===//
-void use::set(value *val){
-  val_ = val;
-  val_->add_use(*this);
-}
-
-value *use::operator=(value *rhs){
-  set(rhs);
-  return rhs;
-}
-
-const use &use::operator=(const use &rhs){
-  set(rhs.val_);
-  return rhs;
-}
-
 //===----------------------------------------------------------------------===//
 //                               user class
 //===----------------------------------------------------------------------===//
 void user::set_operand(unsigned i, value *x) {
   assert(i < ops_.size() && "set_operand() out of range!");
   ops_[i] = x;
+  x->add_use(this);
 }
 
 value* user::get_operand(unsigned i) {
@@ -65,17 +53,17 @@ unsigned user::get_num_operands() const {
 }
 
 void user::replace_all_uses_with(value *target) {
-  for(use &u: uses_)
-  if(auto *usr = dynamic_cast<user*>(u.get())){
-    std::cout << "replacing " << this << " by " << target << " in " << usr << std::endl;
-    usr->replace_uses_of_with(this, target);
+  for(auto it = users_.begin(); it != users_.end();){
+    (*it)->replace_uses_of_with(this, target);
+    target->add_use(*it);
+    erase_use(*it++);
   }
 }
 
 void user::replace_uses_of_with(value *before, value *after) {
-  for(use &u: ops_)
-    if(u.get() == before)
-      u.set(after);
+  for(size_t i = 0; i < ops_.size(); i++)
+    if(ops_[i] == before)
+      ops_[i] = after;
 }
 
 }