Replace arena_alloc with arena_calloc

Changed all structure allocations to use arena_calloc instead of arena_alloc
to ensure zero-initialization and eliminate undefined behavior from accessing
uninitialized memory. This fixes sanitizer errors related to:
- block_t, var_t, basic_block_t structures in parsing
- insn_t structures in SSA passes
- ph2_ir_t structures in register allocation
- constant_t, alias_t, macro_t structures in symbol management

Author: jserv

src/globals.c

@@ -308,17 +308,17 @@ symbol_t *arena_alloc_symbol(void)
 
 constant_t *arena_alloc_constant(void)
 {
-    return arena_alloc(GENERAL_ARENA, sizeof(constant_t));
+    return arena_calloc(GENERAL_ARENA, 1, sizeof(constant_t));
 }
 
 alias_t *arena_alloc_alias(void)
 {
-    return arena_alloc(GENERAL_ARENA, sizeof(alias_t));
+    return arena_calloc(GENERAL_ARENA, 1, sizeof(alias_t));
 }
 
 macro_t *arena_alloc_macro(void)
 {
-    return arena_alloc(GENERAL_ARENA, sizeof(macro_t));
+    return arena_calloc(GENERAL_ARENA, 1, sizeof(macro_t));
 }
 
 bb_traversal_args_t *arena_alloc_traversal_args(void)
@@ -614,7 +614,7 @@ ph2_ir_t *add_existed_ph2_ir(ph2_ir_t *ph2_ir)
 
 ph2_ir_t *add_ph2_ir(opcode_t op)
 {
-    ph2_ir_t *ph2_ir = arena_alloc(BB_ARENA, sizeof(ph2_ir_t));
+    ph2_ir_t *ph2_ir = arena_calloc(BB_ARENA, 1, sizeof(ph2_ir_t));
     ph2_ir->op = op;
     /* Set safe defaults; arch-lowering may annotate later */
     ph2_ir->next = NULL;
@@ -631,7 +631,7 @@ void set_var_liveout(var_t *var, int end)
 
 block_t *add_block(block_t *parent, func_t *func, macro_t *macro)
 {
-    block_t *blk = arena_alloc(BLOCK_ARENA, sizeof(block_t));
+    block_t *blk = arena_calloc(BLOCK_ARENA, 1, sizeof(block_t));
 
     blk->parent = parent;
     blk->func = func;
@@ -885,7 +885,7 @@ func_t *find_func(char *func_name)
 /* Create a basic block and set the scope of variables to 'parent' block */
 basic_block_t *bb_create(block_t *parent)
 {
-    basic_block_t *bb = arena_alloc(BB_ARENA, sizeof(basic_block_t));
+    basic_block_t *bb = arena_calloc(BB_ARENA, 1, sizeof(basic_block_t));
 
     for (int i = 0; i < MAX_BB_PRED; i++) {
         bb->prev[i].bb = NULL;
@@ -1001,7 +1001,7 @@ void add_insn(block_t *block,
 
     bb->scope = block;
 
-    insn_t *n = arena_alloc(INSN_ARENA, sizeof(insn_t));
+    insn_t *n = arena_calloc(INSN_ARENA, 1, sizeof(insn_t));
     n->opcode = op;
     n->rd = rd;
     n->rs1 = rs1;

src/parser.c

@@ -50,7 +50,7 @@ var_t *require_var(block_t *blk)
         var_list->elements = new_locals;
     }
 
-    var_t *var = arena_alloc(BLOCK_ARENA, sizeof(var_t));
+    var_t *var = arena_calloc(BLOCK_ARENA, 1, sizeof(var_t));
     var_list->elements[var_list->size++] = var;
     var->consumed = -1;
     var->base = var;
@@ -3792,7 +3792,7 @@ void parse_internal(void)
     /* set starting point of global stack manually */
     GLOBAL_FUNC = add_func("", true);
     GLOBAL_FUNC->stack_size = 4;
-    GLOBAL_FUNC->bbs = arena_alloc(BB_ARENA, sizeof(basic_block_t));
+    GLOBAL_FUNC->bbs = arena_calloc(BB_ARENA, 1, sizeof(basic_block_t));
 
     /* built-in types */
     TY_void = add_named_type("void");
@@ -3829,7 +3829,7 @@ void parse_internal(void)
     func->return_def.type = TY_int;
     func->num_params = 0;
     func->va_args = 1;
-    func->bbs = arena_alloc(BB_ARENA, sizeof(basic_block_t));
+    func->bbs = arena_calloc(BB_ARENA, 1, sizeof(basic_block_t));
 
     /* lexer initialization */
     SOURCE->size = 0;

src/reg-alloc.c

@@ -53,7 +53,7 @@ void refresh(basic_block_t *bb, insn_t *insn)
 
 ph2_ir_t *bb_add_ph2_ir(basic_block_t *bb, opcode_t op)
 {
-    ph2_ir_t *n = arena_alloc(BB_ARENA, sizeof(ph2_ir_t));
+    ph2_ir_t *n = arena_calloc(BB_ARENA, 1, sizeof(ph2_ir_t));
     n->op = op;
     /* Ensure deterministic defaults for newly created IR nodes */
     n->next = NULL;            /* well-formed singly linked list */

src/ssa.c

@@ -583,7 +583,7 @@ bool insert_phi_insn(basic_block_t *bb, var_t *var)
         return false;
 
     insn_t *head = bb->insn_list.head;
-    insn_t *n = arena_alloc(INSN_ARENA, sizeof(insn_t));
+    insn_t *n = arena_calloc(INSN_ARENA, 1, sizeof(insn_t));
     n->opcode = OP_phi;
     n->rd = var;
     n->rs1 = var;
@@ -805,7 +805,7 @@ void solve_phi_params(void)
 
 void append_unwound_phi_insn(basic_block_t *bb, var_t *dest, var_t *rs)
 {
-    insn_t *n = arena_alloc(INSN_ARENA, sizeof(insn_t));
+    insn_t *n = arena_calloc(INSN_ARENA, 1, sizeof(insn_t));
     n->opcode = OP_unwound_phi;
     n->rd = dest;
     n->rs1 = rs;