Implement comparison operators

TODO

@@ -15,6 +15,8 @@
 - It seems instructions are correctly encoded only if the compiler is running
   on a little endian architecture.
 - Merge declaration and definition nodes.
+- Pointer.
+- Static array.
 
 # Shell
 - Persist the history.

backend/riscv.cpp

@@ -235,11 +235,13 @@ namespace elna::riscv
     void visitor::visit(source::call_statement *statement)
     {
         std::size_t argument_offset{ 0 };
+
         for (auto& argument : statement->arguments())
         {
             argument->accept(this);
+            const auto free_register = this->register_in_use ? x_register::a0 : x_register::t0;
             this->instructions.push_back(instruction(base_opcode::store)
-                    .s(argument_offset, funct3_t::sw, x_register::sp, x_register::a0));
+                    .s(argument_offset, funct3_t::sw, x_register::sp, free_register));
             argument_offset += 4;
         }
         relocate(statement->name(), address_t::text);
@@ -321,19 +323,21 @@ namespace elna::riscv
 
         this->register_in_use = true;
         expression->lhs().accept(this);
+        auto lhs_stack_position = this->variable_counter * 4;
+        ++this->variable_counter;
 
-        this->instructions.push_back( // movl %eax, -x(%rbp); where x is a number.
+        this->instructions.push_back(
             instruction(base_opcode::store)
-                .s(static_cast<std::uint32_t>(this->variable_counter * 4), funct3_t::sw, x_register::sp, x_register::a0)
+                .s(static_cast<std::uint32_t>(lhs_stack_position), funct3_t::sw, x_register::sp, x_register::a0)
         );
-        auto lhs_stack_position = ++this->variable_counter;
 
         this->register_in_use = false;
         expression->rhs().accept(this);
+        this->register_in_use = lhs_register == x_register::a0; // Restore.
 
          this->instructions.push_back(instruction(base_opcode::load)
             .i(x_register::a0, funct3_t::lw, x_register::sp,
-                static_cast<std::int8_t>((lhs_stack_position - 1) * 4))
+                static_cast<std::int8_t>(lhs_stack_position))
         );
 
         // Calculate the result and assign it to a variable on the stack.
@@ -355,6 +359,38 @@ namespace elna::riscv
                 this->instructions.push_back(instruction(base_opcode::op)
                     .r(lhs_register, funct3_t::div, x_register::a0, x_register::t0, funct7_t::muldiv));
                 break;
+            case source::binary_operator::equals:
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::sub, x_register::a0, x_register::t0, funct7_t::sub));
+                this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(lhs_register, funct3_t::sltiu, lhs_register, 1));
+                break;
+            case source::binary_operator::not_equals:
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::sub, x_register::a0, x_register::t0, funct7_t::sub));
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::sltu, x_register::zero, lhs_register));
+                break;
+            case source::binary_operator::less:
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::sltu, x_register::a0, x_register::t0));
+                break;
+            case source::binary_operator::greater_equal:
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::sltu, x_register::t0, x_register::a0));
+                break;
+            case source::binary_operator::greater:
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::slt, x_register::a0, x_register::t0));
+                this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(lhs_register, funct3_t::xori, lhs_register, 1));
+                break;
+            case source::binary_operator::less_equal:
+                this->instructions.push_back(instruction(base_opcode::op)
+                    .r(lhs_register, funct3_t::slt, x_register::t0, x_register::a0));
+                this->instructions.push_back(instruction(base_opcode::opImm)
+                    .i(lhs_register, funct3_t::xori, lhs_register, 1));
+                break;
         }
     }
 

include/elna/backend/riscv.hpp

@@ -146,7 +146,8 @@ namespace elna::riscv
         instruction& i(x_register rd, funct3_t funct3, x_register rs1, std::uint32_t immediate);
         instruction& s(std::uint32_t imm, funct3_t funct3, x_register rs1, x_register rs2);
         instruction& b(std::uint32_t imm, funct3_t funct3, x_register rs1, x_register rs2);
-        instruction& r(x_register rd, funct3_t funct3, x_register rs1, x_register rs2, funct7_t funct7 = funct7_t::none);
+        instruction& r(x_register rd, funct3_t funct3, x_register rs1, x_register rs2,
+                funct7_t funct7 = funct7_t::none);
         instruction& u(x_register rd, std::uint32_t imm);
         instruction& j(x_register rd, std::uint32_t imm);
 

include/elna/source/lexer.hpp

@@ -73,9 +73,10 @@ namespace elna::source
             colon,
             when,
             then,
-            _while,
+            loop,
             _do,
-            procedure
+            procedure,
+            comparison_operator
         };
 
         /**

include/elna/source/parser.hpp

@@ -11,7 +11,13 @@ namespace elna::source
         sum,
         subtraction,
         multiplication,
-        division
+        division,
+        equals,
+        not_equals,
+        less,
+        greater,
+        less_equal,
+        greater_equal
     };
 
     class declaration;
@@ -280,6 +286,7 @@ namespace elna::source
         std::unique_ptr<expression> parse_factor();
         std::unique_ptr<expression> parse_term();
         std::unique_ptr<expression> parse_expression();
+        std::unique_ptr<expression> parse_condition();
         std::unique_ptr<constant_definition> parse_constant_definition();
         std::unique_ptr<procedure_definition> parse_procedure_definition();
         std::unique_ptr<declaration> parse_declaration();

source/lexer.cpp

@@ -204,7 +204,8 @@ namespace elna::source
     {
         return of() == type::identifier
             || of() == type::term_operator
-            || of() == type::factor_operator;
+            || of() == type::factor_operator
+            || of() == type::comparison_operator;
     }
 
     bool token::is_numeric() const noexcept
@@ -257,12 +258,14 @@ namespace elna::source
                 return "«if»";
             case type::then:
                 return "«then»";
-            case type::_while:
+            case type::loop:
                 return "«while»";
             case type::_do:
                 return "«do»";
             case type::procedure:
                 return "«proc»";
+            case type::comparison_operator:
+                return "«comparison_operator»";
         };
         assert(false);
     }
@@ -446,7 +449,7 @@ namespace elna::source
                 }
                 else if (word == "while")
                 {
-                    tokens.emplace_back(token::type::_while, iterator.position());
+                    tokens.emplace_back(token::type::loop, iterator.position());
                 }
                 else if (word == "do")
                 {
@@ -477,12 +480,49 @@ namespace elna::source
 
                 tokens.emplace_back(token::type::term_operator, _operator.c_str(), iterator.position());
             }
+            else if (*iterator == '/' && iterator + 1 != text_end && *(iterator + 1) == '=')
+            {
+                tokens.emplace_back(token::type::comparison_operator, "n", iterator.position());
+                ++iterator;
+            }
             else if (*iterator == '*' || *iterator == '/')
             {
                 std::string _operator{ *iterator };
 
                 tokens.emplace_back(token::type::factor_operator, _operator.c_str(), iterator.position());
             }
+            else if (*iterator == '<')
+            {
+                std::string _operator;
+                auto operator_position = iterator.position();
+
+                if (iterator + 1 == text_end || *(iterator + 1) != '=')
+                {
+                    _operator.push_back(*iterator);
+                }
+                else
+                {
+                    ++iterator;
+                    _operator.push_back('l');
+                }
+                tokens.emplace_back(token::type::comparison_operator, _operator.c_str(), operator_position);
+            }
+            else if (*iterator == '>')
+            {
+                std::string _operator;
+                auto operator_position = iterator.position();
+
+                if (iterator + 1 == text_end || *(iterator + 1) != '=')
+                {
+                    _operator.push_back(*iterator);
+                }
+                else
+                {
+                    ++iterator;
+                    _operator.push_back('g');
+                }
+                tokens.emplace_back(token::type::comparison_operator, _operator.c_str(), operator_position);
+            }
             else if (*iterator == ':' && iterator + 1 != text_end && *(iterator + 1) == '=')
             {
                 tokens.emplace_back(token::type::assignment, iterator.position());

source/parser.cpp

@@ -262,6 +262,24 @@ namespace elna::source
             case '/':
                 this->m_operator = binary_operator::division;
                 break;
+            case '=':
+                this->m_operator = binary_operator::equals;
+                break;
+            case 'n':
+                this->m_operator = binary_operator::not_equals;
+                break;
+            case '<':
+                this->m_operator = binary_operator::less;
+                break;
+            case 'l':
+                this->m_operator = binary_operator::less_equal;
+                break;
+            case '>':
+                this->m_operator = binary_operator::greater;
+                break;
+            case 'g':
+                this->m_operator = binary_operator::greater_equal;
+                break;
             default:
                 throw std::logic_error("Invalid binary operator");
         }
@@ -442,7 +460,7 @@ namespace elna::source
         {
             ++iterator;
 
-            auto expression = parse_expression();
+            auto expression = parse_condition();
 
             ++iterator;
 
@@ -489,6 +507,38 @@ namespace elna::source
         return term;
     }
 
+    std::unique_ptr<expression> parser::parse_condition()
+    {
+        std::unique_ptr<expression> lhs;
+
+        if ((lhs = parse_expression()) == nullptr)
+        {
+            return lhs;
+        }
+        unsigned char _operator{ 0 };
+
+        if (iterator.current().of() == source::token::type::equals)
+        {
+            _operator = '=';
+        }
+        else if (iterator.current().of() == source::token::type::comparison_operator)
+        {
+            _operator = iterator->identifier()[0];
+        }
+        else
+        {
+            return lhs;
+        }
+        ++iterator;
+        auto rhs = parse_expression();
+
+        if (rhs == nullptr)
+        {
+            return nullptr;
+        }
+        return std::make_unique<binary_expression>(std::move(lhs), std::move(rhs), _operator);
+    }
+
     std::unique_ptr<constant_definition> parser::parse_constant_definition()
     {
         auto definition_identifier = iterator.advance(token::type::identifier);
@@ -595,7 +645,7 @@ namespace elna::source
         {
             return parse_if_statement();
         }
-        else if (iterator.current(token::type::_while))
+        else if (iterator.current(token::type::loop))
         {
             return parse_while_statement();
         }
@@ -618,7 +668,7 @@ namespace elna::source
             ++iterator;
             return call;
         }
-        while ((argument_expression = parse_expression()) != nullptr)
+        while ((argument_expression = parse_condition()) != nullptr)
         {
             call->arguments().push_back(std::move(argument_expression));
 
@@ -674,7 +724,7 @@ namespace elna::source
         {
             return nullptr;
         }
-        auto rvalue = parse_expression();
+        auto rvalue = parse_condition();
 
         if (rvalue == nullptr)
         {
@@ -689,7 +739,7 @@ namespace elna::source
         {
             return nullptr;
         }
-        auto condition = parse_expression();
+        auto condition = parse_condition();
 
         if (condition == nullptr || !iterator.skip(token::type::then))
         {
@@ -706,11 +756,11 @@ namespace elna::source
 
     std::unique_ptr<while_statement> parser::parse_while_statement()
     {
-        if (!iterator.skip(token::type::_while))
+        if (!iterator.skip(token::type::loop))
         {
             return nullptr;
         }
-        auto condition = parse_expression();
+        auto condition = parse_condition();
 
         if (condition == nullptr || !iterator.skip(token::type::_do))
         {

tests/expectations/print_equals.txt

@@ -0,0 +1,12 @@
+t
+f
+t
+f
+f
+t
+t
+f
+t
+f
+f
+t

tests/print_equals.eln

@@ -0,0 +1,14 @@
+begin
+  writeb(5 = 5);
+  writeb(5 = 4);
+  writeb(5 /= 4);
+  writeb(5 /= 5);
+  writeb(5 < 4);
+  writeb(4 < 5);
+  writeb(5 >= 4);
+  writeb(4 >= 5);
+  writeb(5 > 4);
+  writeb(4 > 5);
+  writeb(5 <= 4);
+  writeb(4 <= 5)
+end.