gas: Generate code for if statement

If statements are now working, the only exception is for the comparators
|| and && that will be addressed in a further commit. Checks tested:

  fn main(): i32 {
    let n: i32 = 11;

    if (n == 11) {
      if n != 12 {
        if n < 12 {
          if n <= 11 {
            if n > 10 {
              if n >= 11 {
                return 42;
              }
            }
          }
        }
      }
    }

    return n;
  }

To compile the && and || a precedence issue must be addressed: they must
have the highest precedence, witch is not working now:

  1 == 2 || 3 != 2

The or should be the higher level of the tree in the example above.

Signed-off-by: Carlos Maniero <carlos@maniero.me>

1 files changed, 67 insertions, 0 deletions

diff --git a/src/gas_assembly_generator.c b/src/gas_assembly_generator.c
index 4b898ed..f63e35b 100644
--- a/src/gas_assembly_generator.c
+++ b/src/gas_assembly_generator.c
@@ -45,6 +45,9 @@ static void
 gas_assembly_generator_compile_block(gas_assembly_generator_t *gen, ast_block_t *block);
 
 static void
+gas_assembly_generator_compile_if_stmt(gas_assembly_generator_t *gen, ast_if_stmt_t *if_stmt);
+
+static void
 gas_assembly_generator_compile_variable(gas_assembly_generator_t *gen, ast_variable_t *variable);
 
 static void
@@ -106,6 +109,7 @@ gas_assembly_generator_init(gas_assembly_generator_t *gen, FILE *stream)
   gen->stream = stream;
   gen->refs = vector_new();
   gen->stack_offset = 0;
+  gen->label_counter = 0;
 }
 
 void
@@ -139,6 +143,8 @@ gas_assembly_generator_compile(gas_assembly_generator_t *gen, ast_node_t *ast)
       gas_assembly_generator_compile_block(gen, &ast->data.block);
       break;
     case AST_IF_STMT:
+      gas_assembly_generator_compile_if_stmt(gen, &ast->data.if_stmt);
+      break;
     case AST_UNKOWN_NODE:
       assert(false && "unreachable");
   }
@@ -336,5 +342,66 @@ gas_assembly_generator_binary_operation(gas_assembly_generator_t *gen, ast_binar
     return;
   }
 
+  if (binary_operation->kind == AST_BINOP_LT || binary_operation->kind == AST_BINOP_GT ||
+      binary_operation->kind == AST_BINOP_EQUAL || binary_operation->kind == AST_BINOP_NOT_EQUAL ||
+      binary_operation->kind == AST_BINOP_AND || binary_operation->kind == AST_BINOP_OR ||
+      binary_operation->kind == AST_BINOP_GT || binary_operation->kind == AST_BINOP_LT ||
+      binary_operation->kind == AST_BINOP_LT_EQUAL || binary_operation->kind == AST_BINOP_GT_EQUAL) {
+    fprintf(gen->stream, "  cmp %%rcx, %%rax\n");
+    return;
+  }
+
   assert(false && "No strategy defined for binary operation");
 }
+
+static void
+gas_assembly_generator_compile_binop_if(gas_assembly_generator_t *gen, ast_node_t *binop_node)
+{
+  assert(binop_node->kind == AST_BINARY_OPERATION);
+
+  char *jump_map[AST_BINOP_N] = {
+    [AST_BINOP_EQUAL] = "jne",   [AST_BINOP_NOT_EQUAL] = "je", [AST_BINOP_LT] = "jge",
+    [AST_BINOP_LT_EQUAL] = "jg", [AST_BINOP_GT] = "jle",       [AST_BINOP_GT_EQUAL] = "jl",
+  };
+
+  char *jumper = jump_map[binop_node->data.binary_operation.kind];
+
+  assert(jumper != NULL);
+
+  gas_assembly_generator_compile(gen, binop_node);
+
+  fprintf(gen->stream, "  %s .IF%ld\n", jumper, gen->label_counter);
+}
+
+static void
+gas_assembly_generator_compile_if_stmt(gas_assembly_generator_t *gen, ast_if_stmt_t *if_stmt)
+{
+  switch (if_stmt->condition->kind) {
+    case AST_LITERAL: {
+      int if_counter = gen->label_counter++;
+
+      assert(if_stmt->condition->data.literal.kind == AST_LITERAL_BOOL);
+
+      if (!if_stmt->condition->data.literal.value.boolean) {
+        fprintf(gen->stream, "  jmp .IF%d\n", if_counter);
+      }
+
+      gas_assembly_generator_compile(gen, if_stmt->body);
+
+      fprintf(gen->stream, ".IF%d:\n", if_counter);
+      break;
+    }
+    case AST_BINARY_OPERATION: {
+      gas_assembly_generator_compile_binop_if(gen, if_stmt->condition);
+
+      int if_counter = gen->label_counter++;
+
+      gas_assembly_generator_compile(gen, if_stmt->body);
+
+      fprintf(gen->stream, ".IF%d:\n", if_counter);
+      break;
+    }
+    default:
+      assert(false);
+  }
+}