From 4fde66e6094b57201d208b8abd3d7715341cd5db Mon Sep 17 00:00:00 2001
From: Fernando Sahmkow <fsahmkow27@gmail.com>
Date: Thu, 27 Jun 2019 18:57:47 -0400
Subject: [PATCH] shader_ir: Add basic goto elimination

---
 src/video_core/shader/ast.cpp | 348 ++++++++++++++++++++++++++++++++--
 src/video_core/shader/ast.h   | 178 ++++++++++++++---
 2 files changed, 486 insertions(+), 40 deletions(-)

diff --git a/src/video_core/shader/ast.cpp b/src/video_core/shader/ast.cpp
index 5d0e85f427..56a1b29f32 100644
--- a/src/video_core/shader/ast.cpp
+++ b/src/video_core/shader/ast.cpp
@@ -11,6 +11,147 @@
 
 namespace VideoCommon::Shader {
 
+ASTZipper::ASTZipper() = default;
+ASTZipper::ASTZipper(ASTNode new_first) : first{}, last{} {
+    first = new_first;
+    last = new_first;
+    ASTNode current = first;
+    while (current) {
+        current->manager = this;
+        last = current;
+        current = current->next;
+    }
+}
+
+void ASTZipper::PushBack(ASTNode new_node) {
+    new_node->previous = last;
+    if (last) {
+        last->next = new_node;
+    }
+    new_node->next.reset();
+    last = new_node;
+    if (!first) {
+        first = new_node;
+    }
+    new_node->manager = this;
+}
+
+void ASTZipper::PushFront(ASTNode new_node) {
+    new_node->previous.reset();
+    new_node->next = first;
+    if (first) {
+        first->previous = first;
+    }
+    first = new_node;
+    if (!last) {
+        last = new_node;
+    }
+    new_node->manager = this;
+}
+
+void ASTZipper::InsertAfter(ASTNode new_node, ASTNode at_node) {
+    if (!at_node) {
+        PushFront(new_node);
+        return;
+    }
+    new_node->previous = at_node;
+    if (at_node == last) {
+        last = new_node;
+    }
+    new_node->next = at_node->next;
+    at_node->next = new_node;
+    new_node->manager = this;
+}
+
+void ASTZipper::SetParent(ASTNode new_parent) {
+    ASTNode current = first;
+    while (current) {
+        current->parent = new_parent;
+        current = current->next;
+    }
+}
+
+void ASTZipper::DetachTail(ASTNode node) {
+    ASSERT(node->manager == this);
+    if (node == first) {
+        first.reset();
+        last.reset();
+        return;
+    }
+
+    last = node->previous;
+    node->previous.reset();
+}
+
+void ASTZipper::DetachSegment(ASTNode start, ASTNode end) {
+    ASSERT(start->manager == this && end->manager == this);
+    ASTNode prev = start->previous;
+    ASTNode post = end->next;
+    if (!prev) {
+        first = post;
+    } else {
+        prev->next = post;
+    }
+    if (!post) {
+        last = prev;
+    } else {
+        post->previous = prev;
+    }
+    start->previous.reset();
+    end->next.reset();
+    ASTNode current = start;
+    bool found = false;
+    while (current) {
+        current->manager = nullptr;
+        current->parent.reset();
+        found |= current == end;
+        current = current->next;
+    }
+    ASSERT(found);
+}
+
+void ASTZipper::DetachSingle(ASTNode node) {
+    ASSERT(node->manager == this);
+    ASTNode prev = node->previous;
+    ASTNode post = node->next;
+    node->previous.reset();
+    node->next.reset();
+    if (!prev) {
+        first = post;
+    } else {
+        prev->next = post;
+    }
+    if (!post) {
+        last = prev;
+    } else {
+        post->previous = prev;
+    }
+
+    node->manager = nullptr;
+    node->parent.reset();
+}
+
+
+void ASTZipper::Remove(ASTNode node) {
+    ASSERT(node->manager == this);
+    ASTNode next = node->next;
+    ASTNode previous = node->previous;
+    if (previous) {
+        previous->next = next;
+    }
+    if (next) {
+        next->previous = previous;
+    }
+    node->parent.reset();
+    node->manager = nullptr;
+    if (node == last) {
+        last = previous;
+    }
+    if (node == first) {
+        first = next;
+    }
+}
+
 class ExprPrinter final {
 public:
     ExprPrinter() = default;
@@ -72,32 +213,39 @@ public:
     void operator()(ASTProgram& ast) {
         scope++;
         inner += "program {\n";
-        for (ASTNode& node : ast.nodes) {
-            Visit(node);
+        ASTNode current = ast.nodes.GetFirst();
+        while (current) {
+            Visit(current);
+            current = current->GetNext();
         }
         inner += "}\n";
         scope--;
     }
 
-    void operator()(ASTIf& ast) {
+    void operator()(ASTIfThen& ast) {
         ExprPrinter expr_parser{};
         std::visit(expr_parser, *ast.condition);
         inner += Ident() + "if (" + expr_parser.GetResult() + ") {\n";
         scope++;
-        for (auto& node : ast.then_nodes) {
-            Visit(node);
+        ASTNode current = ast.nodes.GetFirst();
+        while (current) {
+            Visit(current);
+            current = current->GetNext();
         }
         scope--;
-        if (ast.else_nodes.size() > 0) {
-            inner += Ident() + "} else {\n";
-            scope++;
-            for (auto& node : ast.else_nodes) {
-                Visit(node);
-            }
-            scope--;
-        } else {
-            inner += Ident() + "}\n";
+        inner += Ident() + "}\n";
+    }
+
+    void operator()(ASTIfElse& ast) {
+        inner += Ident() + "else {\n";
+        scope++;
+        ASTNode current = ast.nodes.GetFirst();
+        while (current) {
+            Visit(current);
+            current = current->GetNext();
         }
+        scope--;
+        inner += Ident() + "}\n";
     }
 
     void operator()(ASTBlockEncoded& ast) {
@@ -128,8 +276,10 @@ public:
         std::visit(expr_parser, *ast.condition);
         inner += Ident() + "do {\n";
         scope++;
-        for (auto& node : ast.loop_nodes) {
-            Visit(node);
+        ASTNode current = ast.nodes.GetFirst();
+        while (current) {
+            Visit(current);
+            current = current->GetNext();
         }
         scope--;
         inner += Ident() + "} while (" + expr_parser.GetResult() + ")\n";
@@ -142,6 +292,12 @@ public:
                  (ast.kills ? "discard" : "exit") + ";\n";
     }
 
+    void operator()(ASTBreak& ast) {
+        ExprPrinter expr_parser{};
+        std::visit(expr_parser, *ast.condition);
+        inner += Ident() + "(" + expr_parser.GetResult() + ") -> break;\n";
+    }
+
     std::string& Ident() {
         if (memo_scope == scope) {
             return tabs_memo;
@@ -177,4 +333,164 @@ std::string ASTManager::Print() {
     return printer.GetResult();
 }
 
+#pragma optimize("", off)
+
+void ASTManager::Decompile() {
+    auto it = gotos.begin();
+    while (it != gotos.end()) {
+        ASTNode goto_node = *it;
+        u32 label_index = goto_node->GetGotoLabel();
+        ASTNode label = labels[label_index];
+        if (IndirectlyRelated(goto_node, label)) {
+            while (!DirectlyRelated(goto_node, label)) {
+                MoveOutward(goto_node);
+            }
+        }
+        if (DirectlyRelated(goto_node, label)) {
+            u32 goto_level = goto_node->GetLevel();
+            u32 label_level = goto_node->GetLevel();
+            while (label_level > goto_level) {
+                MoveOutward(goto_node);
+                goto_level++;
+            }
+        }
+        if (label->GetParent() == goto_node->GetParent()) {
+            bool is_loop = false;
+            ASTNode current = goto_node->GetPrevious();
+            while (current) {
+                if (current == label) {
+                    is_loop = true;
+                    break;
+                }
+                current = current->GetPrevious();
+            }
+
+            if (is_loop) {
+                EncloseDoWhile(goto_node, label);
+            } else {
+                EncloseIfThen(goto_node, label);
+            }
+            it = gotos.erase(it);
+            continue;
+        }
+        it++;
+    }
+    /*
+    for (ASTNode label : labels) {
+        auto& manager = label->GetManager();
+        manager.Remove(label);
+    }
+    labels.clear();
+    */
+}
+
+bool ASTManager::IndirectlyRelated(ASTNode first, ASTNode second) {
+    return !(first->GetParent() == second->GetParent() || DirectlyRelated(first, second));
+}
+
+bool ASTManager::DirectlyRelated(ASTNode first, ASTNode second) {
+    if (first->GetParent() == second->GetParent()) {
+        return false;
+    }
+    u32 first_level = first->GetLevel();
+    u32 second_level = second->GetLevel();
+    u32 min_level;
+    u32 max_level;
+    ASTNode max;
+    ASTNode min;
+    if (first_level > second_level) {
+        min_level = second_level;
+        min = second;
+        max_level = first_level;
+        max = first;
+    } else {
+        min_level = first_level;
+        min = first;
+        max_level = second_level;
+        max = second;
+    }
+
+    while (min_level < max_level) {
+        min_level++;
+        min = min->GetParent();
+    }
+
+    return (min->GetParent() == max->GetParent());
+}
+
+void ASTManager::EncloseDoWhile(ASTNode goto_node, ASTNode label) {
+    ASTZipper& zipper = goto_node->GetManager();
+    ASTNode loop_start = label->GetNext();
+    if (loop_start == goto_node) {
+        zipper.Remove(goto_node);
+        return;
+    }
+    ASTNode parent = label->GetParent();
+    Expr condition = goto_node->GetGotoCondition();
+    zipper.DetachSegment(loop_start, goto_node);
+    ASTNode do_while_node = ASTBase::Make<ASTDoWhile>(parent, condition, ASTZipper(loop_start));
+    zipper.InsertAfter(do_while_node, label);
+    ASTZipper* sub_zipper = do_while_node->GetSubNodes();
+    sub_zipper->SetParent(do_while_node);
+    sub_zipper->Remove(goto_node);
+}
+
+void ASTManager::EncloseIfThen(ASTNode goto_node, ASTNode label) {
+    ASTZipper& zipper = goto_node->GetManager();
+    ASTNode if_end = label->GetPrevious();
+    if (if_end == goto_node) {
+        zipper.Remove(goto_node);
+        return;
+    }
+    ASTNode prev = goto_node->GetPrevious();
+    ASTNode parent = label->GetParent();
+    Expr condition = goto_node->GetGotoCondition();
+    Expr neg_condition = MakeExpr<ExprNot>(condition);
+    zipper.DetachSegment(goto_node, if_end);
+    ASTNode if_node = ASTBase::Make<ASTIfThen>(parent, condition, ASTZipper(goto_node));
+    zipper.InsertAfter(if_node, prev);
+    ASTZipper* sub_zipper = if_node->GetSubNodes();
+    sub_zipper->SetParent(if_node);
+    sub_zipper->Remove(goto_node);
+}
+
+void ASTManager::MoveOutward(ASTNode goto_node) {
+    ASTZipper& zipper = goto_node->GetManager();
+    ASTNode parent = goto_node->GetParent();
+    bool is_loop = parent->IsLoop();
+    bool is_if = parent->IsIfThen() || parent->IsIfElse();
+
+    ASTNode prev = goto_node->GetPrevious();
+
+    Expr condition = goto_node->GetGotoCondition();
+    u32 var_index = NewVariable();
+    Expr var_condition = MakeExpr<ExprVar>(var_index);
+    ASTNode var_node = ASTBase::Make<ASTVarSet>(parent, var_index, condition);
+    zipper.DetachSingle(goto_node);
+    zipper.InsertAfter(var_node, prev);
+    goto_node->SetGotoCondition(var_condition);
+    if (is_loop) {
+        ASTNode break_node = ASTBase::Make<ASTBreak>(parent, var_condition);
+        zipper.InsertAfter(break_node, var_node);
+    } else if (is_if) {
+        ASTNode post = var_node->GetNext();
+        if (post) {
+            zipper.DetachTail(post);
+            ASTNode if_node = ASTBase::Make<ASTIfThen>(parent, var_condition, ASTZipper(post));
+            zipper.InsertAfter(if_node, var_node);
+            ASTZipper* sub_zipper = if_node->GetSubNodes();
+            sub_zipper->SetParent(if_node);
+        }
+    } else {
+        UNREACHABLE();
+    }
+    ASTZipper& zipper2 = parent->GetManager();
+    ASTNode next = parent->GetNext();
+    if (is_if && next && next->IsIfElse()) {
+        zipper2.InsertAfter(goto_node, next);
+        return;
+    }
+    zipper2.InsertAfter(goto_node, parent);
+}
+
 } // namespace VideoCommon::Shader
diff --git a/src/video_core/shader/ast.h b/src/video_core/shader/ast.h
index ca71543fba..22ac8884cc 100644
--- a/src/video_core/shader/ast.h
+++ b/src/video_core/shader/ast.h
@@ -18,32 +18,71 @@ namespace VideoCommon::Shader {
 
 class ASTBase;
 class ASTProgram;
-class ASTIf;
+class ASTIfThen;
+class ASTIfElse;
 class ASTBlockEncoded;
 class ASTVarSet;
 class ASTGoto;
 class ASTLabel;
 class ASTDoWhile;
 class ASTReturn;
+class ASTBreak;
 
-using ASTData = std::variant<ASTProgram, ASTIf, ASTBlockEncoded, ASTVarSet, ASTGoto, ASTLabel,
-                             ASTDoWhile, ASTReturn>;
+using ASTData = std::variant<ASTProgram, ASTIfThen, ASTIfElse, ASTBlockEncoded, ASTVarSet, ASTGoto,
+                             ASTLabel, ASTDoWhile, ASTReturn, ASTBreak>;
 
 using ASTNode = std::shared_ptr<ASTBase>;
 
-class ASTProgram {
-public:
-    ASTProgram() = default;
-    std::list<ASTNode> nodes;
+enum class ASTZipperType : u32 {
+    Program,
+    IfThen,
+    IfElse,
+    Loop,
 };
 
-class ASTIf {
+class ASTZipper final {
 public:
-    ASTIf(Expr condition, std::list<ASTNode> then_nodes, std::list<ASTNode> else_nodes)
-        : condition(condition), then_nodes{then_nodes}, else_nodes{then_nodes} {}
+    ASTZipper();
+    ASTZipper(ASTNode first);
+
+    ASTNode GetFirst() {
+        return first;
+    }
+
+    ASTNode GetLast() {
+        return last;
+    }
+
+    void PushBack(ASTNode new_node);
+    void PushFront(ASTNode new_node);
+    void InsertAfter(ASTNode new_node, ASTNode at_node);
+    void SetParent(ASTNode new_parent);
+    void DetachTail(ASTNode node);
+    void DetachSingle(ASTNode node);
+    void DetachSegment(ASTNode start, ASTNode end);
+    void Remove(ASTNode node);
+
+    ASTNode first{};
+    ASTNode last{};
+};
+
+class ASTProgram {
+public:
+    ASTProgram() : nodes{} {};
+    ASTZipper nodes;
+};
+
+class ASTIfThen {
+public:
+    ASTIfThen(Expr condition, ASTZipper nodes) : condition(condition), nodes{nodes} {}
     Expr condition;
-    std::list<ASTNode> then_nodes;
-    std::list<ASTNode> else_nodes;
+    ASTZipper nodes;
+};
+
+class ASTIfElse {
+public:
+    ASTIfElse(ASTZipper nodes) : nodes{nodes} {}
+    ASTZipper nodes;
 };
 
 class ASTBlockEncoded {
@@ -75,10 +114,9 @@ public:
 
 class ASTDoWhile {
 public:
-    ASTDoWhile(Expr condition, std::list<ASTNode> loop_nodes)
-        : condition(condition), loop_nodes{loop_nodes} {}
+    ASTDoWhile(Expr condition, ASTZipper nodes) : condition(condition), nodes{nodes} {}
     Expr condition;
-    std::list<ASTNode> loop_nodes;
+    ASTZipper nodes;
 };
 
 class ASTReturn {
@@ -88,6 +126,12 @@ public:
     bool kills;
 };
 
+class ASTBreak {
+public:
+    ASTBreak(Expr condition) : condition{condition} {}
+    Expr condition;
+};
+
 class ASTBase {
 public:
     explicit ASTBase(ASTNode parent, ASTData data) : parent{parent}, data{data} {}
@@ -111,9 +155,9 @@ public:
 
     u32 GetLevel() const {
         u32 level = 0;
-        auto next = parent;
-        while (next) {
-            next = next->GetParent();
+        auto next_parent = parent;
+        while (next_parent) {
+            next_parent = next_parent->GetParent();
             level++;
         }
         return level;
@@ -123,15 +167,83 @@ public:
         return &data;
     }
 
+    ASTNode GetNext() {
+        return next;
+    }
+
+    ASTNode GetPrevious() {
+        return previous;
+    }
+
+    ASTZipper& GetManager() {
+        return *manager;
+    }
+
+    u32 GetGotoLabel() const {
+        auto inner = std::get_if<ASTGoto>(&data);
+        if (inner) {
+            return inner->label;
+        }
+        return -1;
+    }
+
+    Expr GetGotoCondition() const {
+        auto inner = std::get_if<ASTGoto>(&data);
+        if (inner) {
+            return inner->condition;
+        }
+        return nullptr;
+    }
+
+    void SetGotoCondition(Expr new_condition) {
+        auto inner = std::get_if<ASTGoto>(&data);
+        if (inner) {
+            inner->condition = new_condition;
+        }
+    }
+
+    bool IsIfThen() const {
+        return std::holds_alternative<ASTIfThen>(data);
+    }
+
+    bool IsIfElse() const {
+        return std::holds_alternative<ASTIfElse>(data);
+    }
+
+    bool IsLoop() const {
+        return std::holds_alternative<ASTDoWhile>(data);
+    }
+
+    ASTZipper* GetSubNodes() {
+        if (std::holds_alternative<ASTProgram>(data)) {
+            return &std::get_if<ASTProgram>(&data)->nodes;
+        }
+        if (std::holds_alternative<ASTIfThen>(data)) {
+            return &std::get_if<ASTIfThen>(&data)->nodes;
+        }
+        if (std::holds_alternative<ASTIfElse>(data)) {
+            return &std::get_if<ASTIfElse>(&data)->nodes;
+        }
+        if (std::holds_alternative<ASTDoWhile>(data)) {
+            return &std::get_if<ASTDoWhile>(&data)->nodes;
+        }
+        return nullptr;
+    }
+
 private:
+    friend class ASTZipper;
+
     ASTData data;
     ASTNode parent;
+    ASTNode next{};
+    ASTNode previous{};
+    ASTZipper* manager{};
 };
 
 class ASTManager final {
 public:
     explicit ASTManager() {
-        main_node = ASTBase::Make<ASTProgram>(nullptr);
+        main_node = ASTBase::Make<ASTProgram>(ASTNode{});
         program = std::get_if<ASTProgram>(main_node->GetInnerData());
     }
 
@@ -147,31 +259,49 @@ public:
         u32 index = labels_map[address];
         ASTNode label = ASTBase::Make<ASTLabel>(main_node, index);
         labels[index] = label;
-        program->nodes.push_back(label);
+        program->nodes.PushBack(label);
     }
 
     void InsertGoto(Expr condition, u32 address) {
         u32 index = labels_map[address];
         ASTNode goto_node = ASTBase::Make<ASTGoto>(main_node, condition, index);
         gotos.push_back(goto_node);
-        program->nodes.push_back(goto_node);
+        program->nodes.PushBack(goto_node);
     }
 
     void InsertBlock(u32 start_address, u32 end_address) {
         ASTNode block = ASTBase::Make<ASTBlockEncoded>(main_node, start_address, end_address);
-        program->nodes.push_back(block);
+        program->nodes.PushBack(block);
     }
 
     void InsertReturn(Expr condition, bool kills) {
         ASTNode node = ASTBase::Make<ASTReturn>(main_node, condition, kills);
-        program->nodes.push_back(node);
+        program->nodes.PushBack(node);
     }
 
     std::string Print();
 
-    void Decompile() {}
+    void Decompile();
+
+
 
 private:
+    bool IndirectlyRelated(ASTNode first, ASTNode second);
+
+    bool DirectlyRelated(ASTNode first, ASTNode second);
+
+    void EncloseDoWhile(ASTNode goto_node, ASTNode label);
+
+    void EncloseIfThen(ASTNode goto_node, ASTNode label);
+
+    void MoveOutward(ASTNode goto_node) ;
+
+    u32 NewVariable() {
+        u32 new_var = variables;
+        variables++;
+        return new_var;
+    }
+
     std::unordered_map<u32, u32> labels_map{};
     u32 labels_count{};
     std::vector<ASTNode> labels{};