Move the CFG generator driver to builder_context.cpp

Author: VedantParanjape

include/blocks/basic_blocks.h

@@ -14,6 +14,7 @@ class basic_block {
         std::vector<std::shared_ptr<basic_block>> successor;
         block::expr::Ptr branch_expr;
         block::stmt::Ptr parent;
+        unsigned int index;
         std::string name;
 };
 

include/blocks/loop_finder.h

@@ -2,7 +2,6 @@
 #define LOOP_FINDER_H
 #include "blocks/block_visitor.h"
 #include "blocks/stmt.h"
-#include "blocks/basic_blocks.h"
 
 namespace block {
 class loop_finder : public block_visitor {

include/builder/builder_context.h

@@ -1,5 +1,6 @@
 #ifndef BUILDER_CONTEXT
 #define BUILDER_CONTEXT
+#include "blocks/basic_blocks.h"
 #include "blocks/expr.h"
 #include "blocks/stmt.h"
 #include "builder/forward_declarations.h"

src/blocks/basic_blocks.cpp

@@ -12,6 +12,7 @@ std::vector<std::shared_ptr<basic_block>> generate_basic_blocks(block::stmt_bloc
     for (auto st: ast->stmts) {
         auto bb = std::make_shared<basic_block>(std::to_string(basic_block_count));
         bb->parent = st;
+        // bb->index = ;
         work_list.push_back(bb);
         basic_block_count++;
     }
@@ -21,7 +22,7 @@ std::vector<std::shared_ptr<basic_block>> generate_basic_blocks(block::stmt_bloc
         work_list[i]->successor.push_back(work_list[i+1]);
     }
 
-    // step 3: process blocks
+    // step 3: process blocks: every xx_stmt type statement is made out into a basic block
     while (work_list.size()) {
         auto bb = work_list.front();
 
@@ -31,22 +32,30 @@ std::vector<std::shared_ptr<basic_block>> generate_basic_blocks(block::stmt_bloc
 
             if (stmt_block_->stmts.size() > 0) {
                 std::vector<std::shared_ptr<basic_block>> stmt_block_list;
-
+                
+                // convert all statements of this stmt_block into a basic block
                 for (auto st: stmt_block_->stmts) {
                     stmt_block_list.push_back(std::make_shared<basic_block>(std::to_string(basic_block_count++)));
                     stmt_block_list.back()->parent = st;
                 }
-
+                
+                // set the basic block successors
                 for (unsigned i = 0; stmt_block_list.size() != 0 && i < stmt_block_list.size() - 1; i++) {
                     stmt_block_list[i]->successor.push_back(stmt_block_list[i+1]);
                 }
 
+                // since we insert these stmts between bb1 ---> bb2 ==> bb1 ---> (bb-a1...bb-an) ---> bb2
+                // point the successor of the stmt_block_list to the basic block that bb1's successor 
+                // pointed to. After this, clear the bb1's successor and push the front of stmt_block_list
+                // to bb1's successor list.
                 stmt_block_list.back()->successor.push_back(bb->successor.front());
                 bb->successor.clear();
                 bb->successor.push_back(stmt_block_list.front());
 
+                // push a rather empty-ish basic block, which will branch to the next basic block, or the next statement.
                 return_list.push_back(bb);
                 work_list.pop_front();
+                // now insert the pending blocks to be processed at the front of the work_list
                 work_list.insert(work_list.begin(), stmt_block_list.begin(), stmt_block_list.end());
             }
             else {
@@ -67,7 +76,7 @@ std::vector<std::shared_ptr<basic_block>> generate_basic_blocks(block::stmt_bloc
             exit_bb->parent = std::make_shared<stmt_block>();
             // check if this is the last block, if yes the successor will be empty
             if (bb->successor.size()) {
-                // set the successor to the block that if_stmt pointer to earlier
+                // set the successor to the block that if_stmt successor pointer to earlier
                 exit_bb->successor.push_back(bb->successor.front());
                 // clear the successor block from the if_stmt
                 bb->successor.clear();

src/blocks/loop_finder.cpp

@@ -129,43 +129,21 @@ static void trim_from_parents(std::vector<stmt_block::Ptr> &parents, std::vector
 }
 
 void loop_finder::visit(stmt_block::Ptr a) {
-	std::vector<std::shared_ptr<basic_block>> BBs = generate_basic_blocks(a);
-
-	std::cout << "++++++ basic blocks ++++++ \n";
-	for (auto bb: BBs) {
-		std::cout << bb->name << ":" << "  ; ";
-		for (auto pred: bb->predecessor) {
-			std::cout << pred->name << ", ";
-		}
-		std::cout << "\n";
-		if (bb->branch_expr) {
-			std::cout << "  ";
-			bb->branch_expr->dump(std::cout, 0);
-		}
-		std::cout << "  ";
-		std::cout << "br ";
-		for (auto branches: bb->successor) {
-			std::cout << branches->name << ", ";
+	while (1) {
+		label_stmt::Ptr found_label = nullptr;
+		for (auto stmt : a->stmts) {
+			if (isa<label_stmt>(stmt)) {
+				found_label = to<label_stmt>(stmt);
+			}
 		}
-		std::cout << "\n";
+		if (found_label == nullptr)
+			break;
+		visit_label(found_label, a);
+	}
+	// Once all labels are done, visit the instructions normally
+	for (auto stmt : a->stmts) {
+		stmt->accept(this);
 	}
-	std::cout << "++++++ basic blocks ++++++ \n";
-
-	// while (1) {
-	// 	label_stmt::Ptr found_label = nullptr;
-	// 	for (auto stmt : a->stmts) {
-	// 		if (isa<label_stmt>(stmt)) {
-	// 			found_label = to<label_stmt>(stmt);
-	// 		}
-	// 	}
-	// 	if (found_label == nullptr)
-	// 		break;
-	// 	visit_label(found_label, a);
-	// }
-	// // Once all labels are done, visit the instructions normally
-	// for (auto stmt : a->stmts) {
-	// 	stmt->accept(this);
-	// }
 }
 void loop_finder::visit_label(label_stmt::Ptr a, stmt_block::Ptr parent) {
 

src/builder/builder_context.cpp

@@ -292,6 +292,28 @@ block::stmt::Ptr builder_context::extract_ast_from_function_impl(void) {
 		block::eliminate_redundant_vars(ast);
 	}
 
+	std::vector<std::shared_ptr<basic_block>> BBs = generate_basic_blocks(block::to<block::stmt_block>(ast));
+
+	std::cerr << "++++++ basic blocks ++++++ \n";
+	for (auto bb: BBs) {
+		std::cerr << bb->name << ":" << "  ; ";
+		for (auto pred: bb->predecessor) {
+			std::cerr << pred->name << ", ";
+		}
+		std::cerr << "\n";
+		if (bb->branch_expr) {
+			std::cerr << "  ";
+			bb->branch_expr->dump(std::cerr, 0);
+		}
+		std::cerr << "  ";
+		std::cerr << "br ";
+		for (auto branches: bb->successor) {
+			std::cerr << branches->name << ", ";
+		}
+		std::cerr << "\n";
+	}
+	std::cerr << "++++++ basic blocks ++++++ \n";
+
 	if (feature_unstructured)
 		return ast;