gas: Implement && and || for if statements

Now if statements are complete! The function
%gas_assembly_generator_compile_condition% is generic and will be used
for any other flow-control statment. The only requirement to it work is
having two labels: One to jump when the condition is true, and another
one when the condition is false.

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

2 files changed, 81 insertions, 30 deletions

diff --git a/src/gas_assembly_generator.c b/src/gas_assembly_generator.c
index f63e35b..c85d7a7 100644
--- a/src/gas_assembly_generator.c
+++ b/src/gas_assembly_generator.c
@@ -109,7 +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;
+  gen->cur_label_index = 0;
 }
 
 void
@@ -344,7 +344,6 @@ gas_assembly_generator_binary_operation(gas_assembly_generator_t *gen, ast_binar
 
   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");
@@ -354,51 +353,103 @@ gas_assembly_generator_binary_operation(gas_assembly_generator_t *gen, ast_binar
   assert(false && "No strategy defined for binary operation");
 }
 
+static char *jump_map[AST_BINOP_N] = {
+  [AST_BINOP_EQUAL] = "je",     [AST_BINOP_NOT_EQUAL] = "jne", [AST_BINOP_LT] = "jl",
+  [AST_BINOP_LT_EQUAL] = "jle", [AST_BINOP_GT] = "jg",         [AST_BINOP_GT_EQUAL] = "jge",
+};
+
+static char *inverse_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",
+};
+
 static void
-gas_assembly_generator_compile_binop_if(gas_assembly_generator_t *gen, ast_node_t *binop_node)
+gas_assembly_generator_compile_condition(gas_assembly_generator_t *gen,
+                                         ast_node_t *condition,
+                                         uint64_t true_label_index,
+                                         bool jump_when_true,
+                                         uint64_t false_label_index,
+                                         bool jump_when_false)
 {
-  assert(binop_node->kind == AST_BINARY_OPERATION);
+  assert(condition->kind == AST_BINARY_OPERATION || condition->kind == AST_LITERAL);
+
+  if (condition->kind == AST_LITERAL) {
+    assert(condition->data.literal.kind == AST_LITERAL_BOOL);
+
+    if (jump_when_false && !condition->data.literal.value.boolean) {
+      fprintf(gen->stream, "  jmp .L_%ld\n", false_label_index);
+      return;
+    }
+
+    if (jump_when_true && condition->data.literal.value.boolean) {
+      fprintf(gen->stream, "  jmp .L_%ld\n", true_label_index);
+    }
+
+    return;
+  }
+
+  if (condition->data.binary_operation.kind == AST_BINOP_OR) {
+    uint64_t or_false_branch_label_index = gen->cur_label_index++;
+
+    gas_assembly_generator_compile_condition(
+      gen, condition->data.binary_operation.left, true_label_index, true, or_false_branch_label_index, false);
+
+    fprintf(gen->stream, ".L_%ld:\n", or_false_branch_label_index);
+
+    gas_assembly_generator_compile_condition(
+      gen, condition->data.binary_operation.right, true_label_index, false, false_label_index, true);
+    return;
+  }
+
+  if (condition->data.binary_operation.kind == AST_BINOP_AND) {
+    uint64_t and_true_branch_label_index = gen->cur_label_index++;
 
-  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",
-  };
+    gas_assembly_generator_compile_condition(
+      gen, condition->data.binary_operation.left, and_true_branch_label_index, false, false_label_index, true);
 
-  char *jumper = jump_map[binop_node->data.binary_operation.kind];
+    fprintf(gen->stream, ".L_%ld:\n", and_true_branch_label_index);
 
-  assert(jumper != NULL);
+    gas_assembly_generator_compile_condition(
+      gen, condition->data.binary_operation.right, true_label_index, false, false_label_index, true);
+    return;
+  }
+
+  gas_assembly_generator_compile(gen, condition);
+
+  if (jump_when_false) {
+    char *jumper = inverse_jump_map[condition->data.binary_operation.kind];
+
+    assert(jumper != NULL);
+
+    fprintf(gen->stream, "  %s .L_%ld\n", jumper, false_label_index);
+    return;
+  }
+
+  if (jump_when_true) {
+    char *jumper = jump_map[condition->data.binary_operation.kind];
 
-  gas_assembly_generator_compile(gen, binop_node);
+    assert(jumper != NULL);
 
-  fprintf(gen->stream, "  %s .IF%ld\n", jumper, gen->label_counter);
+    fprintf(gen->stream, "  %s .L_%ld\n", jumper, true_label_index);
+  }
 }
 
 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_BINARY_OPERATION:
     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);
+      uint64_t true_label_index = gen->cur_label_index++;
+      uint64_t false_label_index = gen->cur_label_index++;
 
-      int if_counter = gen->label_counter++;
+      gas_assembly_generator_compile_condition(
+        gen, if_stmt->condition, true_label_index, false, false_label_index, true);
 
+      fprintf(gen->stream, ".L_%ld:\n", true_label_index);
       gas_assembly_generator_compile(gen, if_stmt->body);
 
-      fprintf(gen->stream, ".IF%d:\n", if_counter);
+      fprintf(gen->stream, ".L_%ld:\n", false_label_index);
       break;
     }
     default:
diff --git a/src/gas_assembly_generator.h b/src/gas_assembly_generator.h
index 3d9a43c..2e195fb 100644
--- a/src/gas_assembly_generator.h
+++ b/src/gas_assembly_generator.h
@@ -46,7 +46,7 @@ typedef struct gas_assembly_generator_t
   FILE *stream;
   vector_t *refs;
   int stack_offset;
-  uint64_t label_counter;
+  uint64_t cur_label_index;
   evaluation_result_t latest_evaluation;
 } gas_assembly_generator_t;