Revise and simplify the -fstruct-return and -fstruct-passing options.

- Rename '-fstruct-return' into '-fstruct-passing', because this emulation affects both function result passing and function argument passing.  Keep '-fstruct-return' as a deprecated synonymous for '-fstruct-passing'
- Remove the ability to change the ABI for struct passing via the '-fstruct-passing=<abi>' and '-fstruct-return=<abi>' command-line flags.  This was more confusing than useful.
- Produce an error if a struct/union is passed as function argument and '-fstruct-passing' is not set.  This used to be supported, using CompCert's default ABI for passing struct arguments.  However, this default ABI does not match any of the standard ABIs of our target platforms, so it is better to reject than to silently produce ABI-incompatible code.

2 files changed, 9 insertions, 33 deletions

diff --git a/driver/Clflags.ml b/driver/Clflags.ml
index 6c2cc661..b67fd638 100644
--- a/driver/Clflags.ml
+++ b/driver/Clflags.ml
@@ -16,9 +16,7 @@ let prepro_options = ref ([]: string list)
 let linker_options = ref ([]: string list)
 let assembler_options = ref ([]: string list)
 let option_flongdouble = ref false
-let option_fstruct_return = ref false
-let option_fstruct_return_style = ref Configuration.struct_return_style
-let option_fstruct_passing_style = ref Configuration.struct_passing_style
+let option_fstruct_passing = ref false
 let option_fbitfields = ref false
 let option_fvararg_calls = ref true
 let option_funprototyped = ref true
diff --git a/driver/Driver.ml b/driver/Driver.ml
index 8d144ad5..9b0e8f13 100644
--- a/driver/Driver.ml
+++ b/driver/Driver.ml
@@ -120,7 +120,7 @@ let parse_c_file sourcename ifile =
   (* Simplification options *)
   let simplifs =
     "b" (* blocks: mandatory *)
-  ^ (if !option_fstruct_return then "s" else "")
+  ^ (if !option_fstruct_passing then "s" else "")
   ^ (if !option_fbitfields then "f" else "")
   ^ (if !option_fpacked_structs then "p" else "")
   in
@@ -425,11 +425,9 @@ Preprocessing options:
 Language support options (use -fno-<opt> to turn off -f<opt>) :
   -fbitfields    Emulate bit fields in structs [off]
   -flongdouble   Treat 'long double' as 'double' [off]
-  -fstruct-return  Emulate returning structs and unions by value [off]
-  -fstruct-return=<convention>
-                 Set the calling conventions used to return structs by value
-  -fstruct-passing=<convention>
-                 Set the calling conventions used to pass structs by value
+  -fstruct-passing  Support passing structs and unions by value as function
+                    results or function arguments [off]
+  -fstruct-return   Like -fstruct-passing (deprecated)
   -fvararg-calls Support calls to variable-argument functions [on]
   -funprototyped Support calls to old-style functions without prototypes [on]
   -fpacked-structs  Emulate packed structs [off]
@@ -502,7 +500,7 @@ let print_version_and_exit _ =
 
 let language_support_options = [
   option_fbitfields; option_flongdouble;
-  option_fstruct_return; option_fvararg_calls; option_funprototyped;
+  option_fstruct_passing; option_fvararg_calls; option_funprototyped;
   option_fpacked_structs; option_finline_asm
 ]
 
@@ -611,33 +609,13 @@ let cmdline_actions =
   Exact "-quiet", Self (fun _ -> Interp.trace := 0);
   Exact "-trace", Self (fun _ -> Interp.trace := 2);
   Exact "-random", Self (fun _ -> Interp.mode := Interp.Random);
-  Exact "-all", Self (fun _ -> Interp.mode := Interp.All);
-(* Special -f options *)
-  Exact "-fstruct-passing=ref-callee",
-    Self (fun _ -> option_fstruct_passing_style := Configuration.SP_ref_callee);
-  Exact "-fstruct-passing=ref-caller",
-    Self (fun _ -> option_fstruct_return := true;
-                   option_fstruct_passing_style := Configuration.SP_ref_caller);
-  Exact "-fstruct-passing=ints",
-    Self (fun _ -> option_fstruct_return := true;
-                   option_fstruct_passing_style := Configuration.SP_split_args);
-  Exact "-fstruct-return=ref",
-    Self (fun _ -> option_fstruct_return := true;
-                   option_fstruct_return_style := Configuration.SR_ref);
-  Exact "-fstruct-return=int1248",
-    Self (fun _ -> option_fstruct_return := true;
-                   option_fstruct_return_style := Configuration.SR_int1248);
-  Exact "-fstruct-return=int1-4",
-    Self (fun _ -> option_fstruct_return := true;
-                   option_fstruct_return_style := Configuration.SR_int1to4);
-  Exact "-fstruct-return=int1-8",
-    Self (fun _ -> option_fstruct_return := true;
-                   option_fstruct_return_style := Configuration.SR_int1to8)
+  Exact "-all", Self (fun _ -> Interp.mode := Interp.All)
   ]
 (* -f options: come in -f and -fno- variants *)
 (* Language support options *)
   @ f_opt "longdouble" option_flongdouble
-  @ f_opt "struct-return" option_fstruct_return
+  @ f_opt "struct-return" option_fstruct_passing
+  @ f_opt "struct-passing" option_fstruct_passing
   @ f_opt "bitfields" option_fbitfields
   @ f_opt "vararg-calls" option_fvararg_calls
   @ f_opt "unprototyped" option_funprototyped