Add const qualifiers to immutable local variables

This applies const qualifier to local variables that are initialized
once and never modified throughout their scope, improving code clarity
by explicitly marking immutable values.

Author: jserv

src/arm-codegen.c

@@ -188,9 +188,9 @@ void emit(int code)
 void emit_ph2_ir(ph2_ir_t *ph2_ir)
 {
     func_t *func;
-    int rd = ph2_ir->dest;
-    int rn = ph2_ir->src0;
-    int rm = ph2_ir->src1;
+    const int rd = ph2_ir->dest;
+    const int rn = ph2_ir->src0;
+    const int rm = ph2_ir->src1;
     int ofs;
 
     /* Prepare this variable to reuse code for:

src/globals.c

@@ -173,16 +173,16 @@ void *arena_alloc(arena_t *arena, int size)
     }
 
     /* Align to sizeof(void*) bytes for host compatibility */
-    int alignment = sizeof(void *);
+    const int alignment = sizeof(void *);
     size = (size + alignment - 1) & ~(alignment - 1);
 
     if (!arena->head || arena->head->offset + size > arena->head->capacity) {
         /* Need a new block: choose capacity = max(DEFAULT_ARENA_SIZE,
          * arena->block_size, size) */
-        int base =
+        const int base =
             (arena->block_size > DEFAULT_ARENA_SIZE ? arena->block_size
                                                     : DEFAULT_ARENA_SIZE);
-        int new_capacity = (size > base ? size : base);
+        const int new_capacity = (size > base ? size : base);
         arena_block_t *new_block = arena_block_create(new_capacity);
         new_block->next = arena->head;
         arena->head = new_block;
@@ -282,7 +282,7 @@ void *arena_realloc(arena_t *arena, char *oldptr, int oldsz, int newsz)
  */
 char *arena_strdup(arena_t *arena, char *str)
 {
-    int n = strlen(str);
+    const int n = strlen(str);
     char *dup = arena_alloc(arena, n + 1);
     memcpy(dup, str, n);
     dup[n] = '\0';
@@ -368,14 +368,14 @@ void arena_free(arena_t *arena)
  */
 int hashmap_hash_index(int size, char *key)
 {
-    int hash = 0x811c9dc5, mask;
+    int hash = 0x811c9dc5;
 
     for (; *key; key++) {
         hash ^= *key;
         hash *= 0x01000193;
     }
 
-    mask = hash >> 31;
+    const int mask = hash >> 31;
     return ((hash ^ mask) - mask) & (size - 1);
 }
 
@@ -431,7 +431,7 @@ hashmap_node_t *hashmap_node_new(char *key, void *val)
     if (!key)
         return NULL;
 
-    int len = strlen(key);
+    const int len = strlen(key);
     hashmap_node_t *node = arena_alloc(HASHMAP_ARENA, sizeof(hashmap_node_t));
 
 

src/opt-sccp.c

@@ -122,7 +122,7 @@ bool simple_sccp(func_t *func)
                 if (insn->rs1 && insn->rs1->is_const && insn->rs2 &&
                     insn->rs2->is_const && !insn->rd->is_global) {
                     int result = 0;
-                    int l = insn->rs1->init_val, r = insn->rs2->init_val;
+                    const int l = insn->rs1->init_val, r = insn->rs2->init_val;
 
                     /* Compute result based on operation type */
                     switch (insn->opcode) {

src/parser.c

@@ -132,7 +132,7 @@ void read_expr(block_t *parent, basic_block_t **bb);
 
 int write_symbol(const char *data)
 {
-    int start_len = elf_data->size;
+    const int start_len = elf_data->size;
     elf_write_str(elf_data, data);
     elf_write_byte(elf_data, 0);
     return start_len;
@@ -1367,7 +1367,7 @@ void read_literal_param(block_t *parent, basic_block_t *bb)
         combined_len += literal_len;
     }
 
-    int index = write_symbol(combined);
+    const int index = write_symbol(combined);
 
     var_t *vd = require_typed_ptr_var(parent, TY_char, true);
     gen_name_to(vd->var_name);

src/reg-alloc.c

@@ -887,9 +887,9 @@ void dump_ph2_ir(void)
     for (int i = 0; i < ph2_ir_idx; i++) {
         ph2_ir_t *ph2_ir = PH2_IR_FLATTEN[i];
 
-        int rd = ph2_ir->dest + 48;
-        int rs1 = ph2_ir->src0 + 48;
-        int rs2 = ph2_ir->src1 + 48;
+        const int rd = ph2_ir->dest + 48;
+        const int rs1 = ph2_ir->src0 + 48;
+        const int rs2 = ph2_ir->src1 + 48;
 
         switch (ph2_ir->op) {
         case OP_define: