From 39315de738e86e1f1beb52ae14101b5caf7486a2 Mon Sep 17 00:00:00 2001
From: Carlos Maniero <carlosmaniero@gmail.com>
Date: Fri, 21 Apr 2023 14:36:28 -0300
Subject: 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>
---
 examples/arithmetics.pipa    |  3 +++
 src/gas_assembly_generator.c | 50 +++++++++++++++++++++++++++++++++++++++-----
 test/integration_test.c      |  1 +
 3 files changed, 49 insertions(+), 5 deletions(-)
 create mode 100644 examples/arithmetics.pipa

diff --git a/examples/arithmetics.pipa b/examples/arithmetics.pipa
new file mode 100644
index 0000000..e2b7645
--- /dev/null
+++ b/examples/arithmetics.pipa
@@ -0,0 +1,3 @@
+main(): i32 {
+  return ((2 + 1) * (5 - 3) + 7) * 2 / 2;
+}
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);
+}
diff --git a/test/integration_test.c b/test/integration_test.c
index a624f8c..0ef3f5d 100644
--- a/test/integration_test.c
+++ b/test/integration_test.c
@@ -46,6 +46,7 @@ test_examples(const  MunitParameter params[],
                  void  *user_data_or_fixture)
 {
   assert_exit_status("../examples/main.pipa", 69);
+  assert_exit_status("../examples/arithmetics.pipa", 13);
 
   return MUNIT_OK;
 }
-- 
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