Added Sub peephole

src/inst.cpp

@@ -40,6 +40,10 @@ void Inst::SetDataInput(id_t index, Inst *inst) {
     if (HasControlProp()) {
         index++;
     }
+    // For dynamic inputs
+    if (index != NumAllInputs() && GetRawInput(index) != nullptr) {
+        GetRawInput(index)->DeleteDataUser(this);
+    }
     SetRawInput(index, inst);
     inst->AddDataUser(this);
 }
@@ -268,9 +272,8 @@ ConstantInst *Inst::CastToConstant() {
 
 void Inst::ReplaceDataUsers(Inst *from) {
     ASSERT(!HasControlProp());
-    for (auto it = from->StartIteratorDataUsers(); it != from->GetRawUsers().end(); it++) {
+    for (auto it = from->StartIteratorDataUsers(); it != from->GetRawUsers().end(); it = from->StartIteratorDataUsers()) {
         auto user = *it;
-        AddDataUser(user);
         for (id_t i = 0; i < user->NumDataInputs(); i++) {
             if (user->GetDataInput(i) == from) {
                 user->SetDataInput(i, this);

src/inst.h

@@ -118,6 +118,15 @@ class Inst
     void AddDataUser(Inst *inst);
     void DeleteDataUser(Inst *inst);
 
+    bool HasSingleDataUser() {
+        return NumDataUsers() == 1;
+    }
+
+    Inst *GetSingleDataUser() {
+        ASSERT(HasSingleDataUser());
+        return GetRawUsers().back();
+    }
+
     const std::list<Inst *> GetDataUsers();
 
     virtual void DumpInputs([[maybe_unused]] std::ostream &out) {};
@@ -205,11 +214,11 @@ class Inst
 
 private:
     bool inst_placed_ = false;
-    id_t id_;
-    LinearNumber linear_number_;
-    LifeNumber life_number_;
-    Opcode opc_;
-    Type type_;
+    id_t id_ {};
+    LinearNumber linear_number_ {};
+    LifeNumber life_number_ {};
+    Opcode opc_ {};
+    Type type_ {};
 
 protected:
     Inst *prev_ = nullptr;

src/optimizations/peepholes.cpp

@@ -35,6 +35,8 @@ void Peepholes::VisitSub(Inst *inst) {
     if (ConstFoldingBinaryOp(graph_, inst)) {
         return;
     }
+    // Some optimization may be applied, so we don't go out from function
+    TryOptimizeSubSub(inst);
 
     if (TryOptimizeSubZero(inst)) {
         return;
@@ -60,6 +62,13 @@ void Peepholes::VisitOr(Inst *inst) {
     }
 }
 
+// 1. Constant 0x0 -> v3
+// 2. ... -> v3
+// 3. Sub v2, v1 -> v4
+// ==========>>==========
+// 1. Constant 0x0
+// 2. ... -> v4
+// 3. Sub v2, v1
 bool Peepholes::TryOptimizeSubZero(Inst *inst) {
     auto input0 = inst->GetDataInput(0);
     auto input1 = inst->GetDataInput(1);
@@ -71,6 +80,41 @@ bool Peepholes::TryOptimizeSubZero(Inst *inst) {
     return false;
 }
 
+// Optimize sub of sub
+// 1. Constant ... -> v3
+// 2. Constant ... -> v3
+// 3. ... -> v4
+// 4. Sub v3, v1 -> v3
+// 5. Sub v4, v2 -> v6
+// ==========>>==========
+// 1. Constant ... -> v3
+// 2. Constant ...
+// 6. Constant /v1+v2/ -> v5
+// 3. ... -> v4
+// 4. Sub v3, v1
+// 5. Sub v3, v6 -> v6
+bool Peepholes::TryOptimizeSubSub(Inst *inst) {
+    auto input0 = inst->GetDataInput(0);
+    auto input1 = inst->GetDataInput(1);
+
+    if (!input1->IsConst() || !inst->HasSingleDataUser()) {
+        return false;
+    }
+
+    auto single_user = inst->GetSingleDataUser();
+    if (single_user->GetOpcode() != Opcode::Sub || !single_user->GetDataInput(1)->IsConst()) {
+        return false;
+    }
+
+    auto const_near = input1->CastToConstant()->GetImm();
+    auto const_far = single_user->GetDataInput(1)->CastToConstant()->GetImm();
+    // Overflow is ok
+    auto new_const = graph_->CreateConstantInst(const_near + const_far);
+    single_user->SetDataInput(1, new_const);
+    single_user->SetDataInput(0, input0);
+    return true;
+}
+
 bool Peepholes::TryOptimizeShlAfterShr(Inst *inst) {
     auto input0 = inst->GetDataInput(0);
     auto input1 = inst->GetDataInput(1);

src/optimizations/peepholes.h

@@ -21,6 +21,7 @@ class Peepholes {
 
     // Cases of optimization
     bool TryOptimizeSubZero(Inst *inst);
+    bool TryOptimizeSubSub(Inst *inst);
     bool TryOptimizeShlAfterShr(Inst *inst);
     bool TryOptimizeOrZero(Inst *inst);
 

tests/peepholes_tests.cpp

@@ -97,6 +97,44 @@ TEST(PeepholesTest, ShrAfterShr) {
     GraphComparator(true_graph, graph).Compare();
 }
 
+TEST(PeepholesTest, SubSub) {
+    // Before
+    auto ic = IrConstructor();
+    ic.CreateInst<Opcode::Start>(0);
+    ic.CreateInst<Opcode::End>(1);
+    ic.CreateInst<Opcode::Parameter>(2);
+    ic.CreateInst<Opcode::Constant>(3).Imm(10);
+    ic.CreateInst<Opcode::Constant>(4).Imm(15);
+    ic.CreateInst<Opcode::Sub>(5).DataInputs(2, 3);
+    ic.CreateInst<Opcode::Sub>(6).DataInputs(5, 4);
+    ic.CreateInst<Opcode::Return>(7).CtrlInput(0).DataInputs(6);
+    ic.CreateInst<Opcode::Jump>(8).CtrlInput(7).JmpTo(1);
+
+    auto graph = ic.GetFinalGraph();
+    auto ph = Peepholes(graph);
+    ph.Run();
+
+    // After
+    auto ic_true = IrConstructor();
+    ic_true.CreateInst<Opcode::Start>(0);
+    ic_true.CreateInst<Opcode::Parameter>(2);
+    ic_true.CreateInst<Opcode::Constant>(3).Imm(10);
+    ic_true.CreateInst<Opcode::Constant>(4).Imm(15);
+    ic_true.CreateInst<Opcode::Constant>(9).Imm(25);
+
+    ic_true.CreateInst<Opcode::Sub>(5).DataInputs(2, 3);
+    ic_true.CreateInst<Opcode::Sub>(6).DataInputs(2, 9);
+    ic_true.CreateInst<Opcode::Return>(7).CtrlInput(0).DataInputs(6);
+    ic_true.CreateInst<Opcode::Jump>(8).CtrlInput(7).JmpTo(1);
+
+    ic_true.CreateInst<Opcode::End>(1);
+
+    auto true_graph = ic_true.GetFinalGraph();
+
+    GraphComparator(true_graph, graph).Compare();
+}
+
+
 
 TEST(ConstFoldingTest, Sub) {
     // Before