Stop model_init() overriding coverage filename

The addition of a `sail_set_coverage_file()` call into `model_init()`
in commit 28ef9e9 seems to have unintentionally restricted the
ability to use `sail_set_coverage_file()` elsewhere.
Any program that calls Sail's `model_init()` after performing
its own `sail_set_coverage_file()` call will now behave differently.
The coverage filename specified at runtime will be overridden,
even if the sail `-c_coverage_output` argument was not used.

This issue was found when using the c_emulator/cheri_riscv_rvfi_RV32
binary generated by the CTSRD-CHERI/sail-cheri-riscv repository.
It calls `model_init()` as part of resetting between tests
when running in a particular multi-test mode.

The addition of the `sail_set_coverage_file()` call into
`model_init()` seems to have been to allow test/sailcov/run_tests.py
to use a coverage filename other than the default ("sail_coverage")
specified in lib/coverage/libsail_coverage.a (generated from
lib/coverage/src/lib.rs).
This can alternately be achieved by adding a `-c` (coverage)
argument to the argument parser included in the "simple_if.bin" binary
built as part of the test, and removing the changes to `model_init()`.
This solution seems to satisfy the original requirement
without the adverse change in behaviour in other programs.

lib/rts.c

@@ -631,6 +631,7 @@ static struct option options[] = {
  {"elf", required_argument, 0, 'e'},
  {"entry", required_argument, 0, 'n'},
  {"image", required_argument, 0, 'i'},
+ {"coverage", required_argument, 0, 'c'},
  {"verbosity", required_argument, 0, 'v'},
  {"help", no_argument, 0, 'h'},
  {0, 0, 0, 0}
@@ -654,7 +655,7 @@ int process_arguments(int argc, char *argv[])
 
  while (true) {
  int option_index = 0;
- c = getopt_long(argc, argv, "e:n:i:b:l:C:v:h", options, &option_index);
+ c = getopt_long(argc, argv, "e:n:i:b:l:C:c:v:h", options, &option_index);
 
  if (c == -1) break;
 
@@ -721,6 +722,14 @@ int process_arguments(int argc, char *argv[])
  }
  break;
 
+ case 'c':
+#ifdef SAIL_COVERAGE_H
+ sail_set_coverage_file(optarg);
+#else
+ fprintf(stderr, "Ignoring flag -c %s. Requires sail arg: -c_include sail_coverage.h", optarg);
+#endif
+ break;
+
  case 'v':
  if (!sscanf(optarg, "0x%" PRIx64, &g_verbosity)) {
  fprintf(stderr, "Could not parse verbosity flags %s\n", optarg);

src/sail_c_backend/c_backend.ml

@@ -90,7 +90,6 @@ let opt_prefix = ref "z"
 let opt_extra_params = ref None
 let opt_extra_arguments = ref None
 let opt_branch_coverage = ref None
-let opt_branch_coverage_output = ref "sail_coverage"
 
 let extra_params () = match !opt_extra_params with Some str -> str ^ ", " | _ -> ""
 
@@ -2058,10 +2057,6 @@ let compile_ast env effect_info output_chan c_includes ast =
  separate hardline
  (List.map string
  ([Printf.sprintf "%svoid model_init(void)" (static ()); "{"; " setup_rts();"]
- @ ( if Option.is_some !opt_branch_coverage then
- [Printf.sprintf " sail_set_coverage_file(\"%s\");" !opt_branch_coverage_output]
- else []
- )
  @ fst exn_boilerplate @ startup cdefs @ letbind_initializers
  @ List.concat (List.map (fun r -> fst (register_init_clear r)) regs)
  @ (if regs = [] then [] else [Printf.sprintf " %s(UNIT);" (sgen_function_id (mk_id "initialize_registers"))])

src/sail_c_backend/c_backend.mli

@@ -111,8 +111,6 @@ val opt_extra_arguments : string option ref
 
 val opt_branch_coverage : out_channel option ref
 
-val opt_branch_coverage_output : string ref
-
 (** Optimization flags *)
 
 val optimize_primops : bool ref

src/sail_c_backend/sail_plugin_c.ml

@@ -104,10 +104,6 @@ let c_options =
  Arg.String (fun str -> C_backend.opt_branch_coverage := Some (open_out str)),
  "<file> Turn on coverage tracking and output information about all branches and functions to a file"
  );
- ( "-c_coverage_output",
- Arg.String (fun str -> C_backend.opt_branch_coverage_output := str),
- "<file> The generated C will output coverage at runtime to the filename provided (default sail_coverage)"
- );
  ( "-O",
  Arg.Tuple
  [

test/sailcov/run_tests.py

@@ -38,9 +38,9 @@ def test_sailcov():
  basename = os.path.splitext(os.path.basename(filename))[0]
  tests[filename] = os.fork()
  if tests[filename] == 0:
- step('{} -no_warn -no_memo_z3 -c -c_include sail_coverage.h -c_coverage {}.branches -c_coverage_output {}.taken {} -o {}'.format(sail, basename, basename, filename, basename))
+ step('{} -no_warn -no_memo_z3 -c -c_include sail_coverage.h -c_coverage {}.branches {} -o {}'.format(sail, basename, filename, basename))
  step('cc {}.c {}/lib/*.c {}/lib/coverage/libsail_coverage.a -lgmp -lz -lpthread -ldl -I {}/lib -o {}.bin'.format(basename, sail_dir, sail_dir, sail_dir, basename))
- step('./{}.bin'.format(basename))
+ step('./{}.bin -c {}.taken'.format(basename, basename))
  step('{} --all {}.branches --taken {}.taken {}'.format(sailcov, basename, basename, filename))
  step('diff {}.html {}.expect'.format(basename, basename))
  print_ok(filename)