markused: reduce unused code by removing unused safe_int fns (#25402)

Author: felipensp

vlib/v/ast/table.v

@@ -26,6 +26,7 @@ pub mut:
 	arr_map        bool            // []map[key]value
 	type_name      bool            // var.type_name()
 	print_options  bool            // print option type
+	safe_int       bool            // needs safe int comparison
 	print_types    map[int]bool    // print() idx types
 	used_fns       map[string]bool // filled in by markused
 	used_consts    map[string]bool // filled in by markused

vlib/v/gen/c/cgen.v

@@ -1003,6 +1003,9 @@ pub fn (mut g Gen) init() {
 		} else {
 			g.cheaders.writeln(c_headers)
 		}
+		if !g.pref.skip_unused || g.table.used_features.safe_int {
+			g.cheaders.writeln(c_unsigned_comparison_functions)
+		}
 		if !g.pref.skip_unused || g.table.used_features.used_attr_weak {
 			g.cheaders.writeln(c_common_weak_attr)
 		}

vlib/v/gen/c/cheaders.v

@@ -309,7 +309,7 @@ const c_helper_macros = '//============================== HELPER C MACROS ======
 #define _PUSH_MANY_noscan(arr, val, tmp, tmp_typ) {tmp_typ tmp = (val); builtin__array_push_many_noscan(arr, tmp.data, tmp.len);}
 '
 
-const c_headers = c_helper_macros + c_unsigned_comparison_functions + c_common_macros +
+const c_headers = c_helper_macros + c_common_macros +
 	r'
 // c_headers
 typedef int (*qsort_callback_func)(const void*, const void*);
@@ -491,7 +491,7 @@ typedef void (*MapCloneFn)(voidptr, voidptr);
 typedef void (*MapFreeFn)(voidptr);
 '
 
-const c_bare_headers = c_helper_macros + c_unsigned_comparison_functions + c_common_macros +
+const c_bare_headers = c_helper_macros + c_common_macros +
 	'
 #define _VFREESTANDING
 typedef long unsigned int size_t;

vlib/v/markused/walker.v

@@ -666,8 +666,15 @@ fn (mut w Walker) expr(node_ ast.Expr) {
 					w.mark_by_sym(right_sym)
 				}
 			}
-			if !w.uses_eq && node.op in [.eq, .ne] {
-				w.uses_eq = true
+			if node.op in [.eq, .ne, .gt, .ge, .lt, .le] {
+				if !w.table.used_features.safe_int && node.left_type != 0 && node.right_type != 0 {
+					left := w.table.unaliased_type(node.left_type)
+					right := w.table.unaliased_type(node.right_type)
+					w.table.used_features.safe_int = (
+						(left.idx() in [ast.u32_type_idx, ast.u64_type_idx] && right.is_signed())
+						|| (right.idx() in [ast.u32_type_idx, ast.u64_type_idx] && left.is_signed()))
+				}
+				w.uses_eq = w.uses_eq || node.op in [.eq, .ne]
 			}
 		}
 		ast.IfGuardExpr {