use the correct frequency for the arm tsc timer

src/check_builtin.cpp

@@ -4713,6 +4713,7 @@ gb_internal bool check_builtin_procedure(CheckerContext *c, Operand *operand, As
 		}
 		break;
 
+	case BuiltinProc_arm64_read_cycle_counter_frequency:
 	case BuiltinProc_read_cycle_counter:
 		operand->mode = Addressing_Value;
 		operand->type = t_i64;

src/checker_builtin_procs.hpp

@@ -225,6 +225,8 @@ BuiltinProc__simd_end,
 	BuiltinProc_x86_cpuid,
 	BuiltinProc_x86_xgetbv,
 
+	BuiltinProc_arm64_read_cycle_counter_frequency,
+
 	// Constant type tests
 
 BuiltinProc__type_begin,
@@ -584,6 +586,7 @@ gb_global BuiltinProc builtin_procs[BuiltinProc_COUNT] = {
 	{STR_LIT("syscall_bsd"), 1, true, Expr_Expr, BuiltinProcPkg_intrinsics, false, true},
 	{STR_LIT("x86_cpuid"),  2, false, Expr_Expr, BuiltinProcPkg_intrinsics},
 	{STR_LIT("x86_xgetbv"), 1, false, Expr_Expr, BuiltinProcPkg_intrinsics},
+	{STR_LIT("arm64_read_cycle_counter_frequency"), 0, false, Expr_Expr, BuiltinProcPkg_intrinsics},
 
 
 	{STR_LIT(""), 0, false, Expr_Stmt, BuiltinProcPkg_intrinsics},

src/llvm_backend_proc.cpp

@@ -2809,6 +2809,19 @@ gb_internal lbValue lb_build_builtin_proc(lbProcedure *p, Ast *expr, TypeAndValu
 			}
 			return res;
 		}
+	case BuiltinProc_arm64_read_cycle_counter_frequency:
+		{
+			lbValue res = {};
+			res.type = tv.type;
+
+			LLVMTypeRef func_type = LLVMFunctionType(LLVMInt64TypeInContext(p->module->ctx), nullptr, 0, false);
+			bool has_side_effects = false;
+			LLVMValueRef the_asm = llvm_get_inline_asm(func_type, str_lit("mrs $0, cntfrq_el0"), str_lit("=r"), has_side_effects);
+			GB_ASSERT(the_asm != nullptr);
+			res.value = LLVMBuildCall2(p->builder, func_type, the_asm, nullptr, 0, "");
+
+			return res;
+		}
 
 	case BuiltinProc_count_trailing_zeros:
 		return lb_emit_count_trailing_zeros(p, lb_build_expr(p, ce->args[0]), tv.type);