gas: Generate arithmetics expressions

We decided for using push and pop to simplify the implementation, we
want to revisit the approach latter.

Signed-off-by: Carlos Maniero <carlosmaniero@gmail.com>
Co-authored-by: Johnny Richard <johnny@johnnyrichard.com>

1 files changed, 45 insertions, 5 deletions

diff --git a/src/gas_assembly_generator.c b/src/gas_assembly_generator.c
index ae4d762..10a67f3 100644
--- a/src/gas_assembly_generator.c
+++ b/src/gas_assembly_generator.c
@@ -22,7 +22,8 @@
 
 static void gas_assembly_generator_visit_function(ast_visitor_t *visitor, ast_function_declaration_t *func);
 static void gas_assembly_generator_visit_return_stmt(ast_visitor_t *visitor, ast_return_stmt_t *return_stmt);
-static void gas_assembly_generator_visit_literal(ast_visitor_t *visitor, ast_literal_t *return_stmt);
+static void gas_assembly_generator_visit_literal(ast_visitor_t *visitor, ast_literal_t *literal);
+static void gas_assembly_generator_binary_operation(ast_visitor_t *visitor, ast_binary_operation_t *binary_operation);
 
 void
 gas_assembly_generator_init(gas_assembly_generator_t *gen, FILE *out)
@@ -31,7 +32,8 @@ gas_assembly_generator_init(gas_assembly_generator_t *gen, FILE *out)
   gen->super = (ast_visitor_t) {
     .visit_function = &gas_assembly_generator_visit_function,
     .visit_literal = &gas_assembly_generator_visit_literal,
-    .visit_return_stmt = &gas_assembly_generator_visit_return_stmt
+    .visit_return_stmt = &gas_assembly_generator_visit_return_stmt,
+    .visit_binary_operation = &gas_assembly_generator_binary_operation
   };
   gen->out = out;
 }
@@ -63,7 +65,7 @@ gas_assembly_generator_visit_return_stmt(ast_visitor_t *visitor, ast_return_stmt
 
   ast_visitor_visit(visitor, return_stmt->argument);
 
-  fprintf(gen->out, "  mov %%eax, %%ebx\n");
+  fprintf(gen->out, "  mov %%rax, %%rbx\n");
   fprintf(gen->out, "  mov $1, %%al\n");
   fprintf(gen->out, "  int $0x80\n");
 }
@@ -74,9 +76,47 @@ gas_assembly_generator_visit_literal(ast_visitor_t *visitor, ast_literal_t *lite
   gas_assembly_generator_t *gen = (gas_assembly_generator_t *) visitor;
   switch (literal->kind) {
     case AST_LITERAL_INTEGER:
-      fprintf(gen->out, "  mov $%d, %%eax\n", literal->value.integer);
+      fprintf(gen->out, "  mov $%d, %%rax\n", literal->value.integer);
       return;
     default:
-      assert(false && "No code generation strategy.");
+      assert(false && "no code generation strategy.");
   }
 }
+
+static void
+gas_assembly_generator_binary_operation(ast_visitor_t *visitor, ast_binary_operation_t *binary_operation)
+{
+  gas_assembly_generator_t *gen = (gas_assembly_generator_t *) visitor;
+
+  ast_visitor_visit(visitor, binary_operation->right);
+
+  fprintf(gen->out, "  push %%rax\n");
+
+  ast_visitor_visit(visitor, binary_operation->left);
+
+  fprintf(gen->out, "  pop %%rcx\n");
+
+  if (string_view_eq(binary_operation->op, string_view_from_str("+"))) {
+    fprintf(gen->out, "  add %%rcx, %%rax\n");
+    return;
+  }
+
+  if (string_view_eq(binary_operation->op, string_view_from_str("-"))) {
+    fprintf(gen->out, "  sub %%rcx, %%rax\n");
+    return;
+  }
+
+  if (string_view_eq(binary_operation->op, string_view_from_str("*"))) {
+    fprintf(gen->out, "  mul %%rcx\n");
+    return;
+  }
+
+  if (string_view_eq(binary_operation->op, string_view_from_str("/"))) {
+    fprintf(gen->out, "  xor %%rdx, %%rdx\n");
+    fprintf(gen->out, "  div %%rcx\n");
+    return;
+  }
+
+  fprintf(stderr, "no strategy defined for: "SVFMT"\n", SVARG(&binary_operation->op));
+  assert(false);
+}