Bitfields: MSB-to-LSB in addition to LSB-to-MSB

git-svn-id: https://yquem.inria.fr/compcert/svn/compcert/trunk@1600 fca1b0fc-160b-0410-b1d3-a4f43f01ea2e

3 files changed, 39 insertions, 11 deletions

diff --git a/cparser/Bitfields.ml b/cparser/Bitfields.ml
index 9452a4f..472b6a4 100644
--- a/cparser/Bitfields.ml
+++ b/cparser/Bitfields.ml
@@ -94,15 +94,22 @@ let rec transf_members env id count = function
         else begin
           (* Create integer field of sufficient size for this bitfield group *)
           let carrier = sprintf "__bf%d" count in
-          let carrier_typ = TInt(unsigned_ikind_for_carrier nbits, []) in
+          let carrier_ikind = unsigned_ikind_for_carrier nbits in
+          let carrier_typ = TInt(carrier_ikind, []) in
+          (* Enter each field with its bit position, size, signedness *)
           List.iter
             (fun (name, pos, sz, signed, signed2) ->
-              if name <> "" then
+              if name <> "" then begin
+                let pos' =
+                  if !config.bitfields_msb_first
+                  then sizeof_ikind carrier_ikind * 8 - pos - sz
+                  else pos in
                 Hashtbl.add bitfield_table
                   (id, name)
                   {bf_carrier = carrier; bf_carrier_typ = carrier_typ;
-                   bf_pos = pos; bf_size = sz;
-                   bf_signed = signed; bf_signed_res = signed2})
+                   bf_pos = pos'; bf_size = sz;
+                   bf_signed = signed; bf_signed_res = signed2}
+              end)
             bitfields;
           { fld_name = carrier; fld_typ = carrier_typ; fld_bitfield = None}
           :: transf_members env id (count + 1) ml'
diff --git a/cparser/Machine.ml b/cparser/Machine.ml
index 21b3daa..ffff5fb 100644
--- a/cparser/Machine.ml
+++ b/cparser/Machine.ml
@@ -39,7 +39,8 @@ type t = {
   alignof_double: int;
   alignof_longdouble: int;
   alignof_void: int option;
-  alignof_fun: int option
+  alignof_fun: int option;
+  bitfields_msb_first: bool
 }
 
 let ilp32ll64 = {
@@ -66,7 +67,8 @@ let ilp32ll64 = {
   alignof_double = 8;
   alignof_longdouble = 16;
   alignof_void = None;
-  alignof_fun = None
+  alignof_fun = None;
+  bitfields_msb_first = false
 }
 
 let i32lpll64 = {
@@ -93,7 +95,8 @@ let i32lpll64 = {
   alignof_double = 8;
   alignof_longdouble = 16;
   alignof_void = None;
-  alignof_fun = None
+  alignof_fun = None;
+  bitfields_msb_first = false
 }
 
 let il32pll64 = {
@@ -120,15 +123,26 @@ let il32pll64 = {
   alignof_double = 8;
   alignof_longdouble = 16;
   alignof_void = None;
-  alignof_fun = None
+  alignof_fun = None;
+  bitfields_msb_first = false
 }
 
-let make_char_signed c = {c with char_signed = true}
+(* Canned configurations for some ABIs *)
+
+let x86_32 = { ilp32ll64 with char_signed = true }
+let x86_64 = { i32lpll64 with char_signed = true }
+let win64 = { il32pll64 with char_signed = true }
+let ppc_32_bigendian = { ilp32ll64 with bitfields_msb_first = true }
+let arm_littleendian = ilp32ll64
+
+(* Add GCC extensions re: sizeof and alignof *)
 
 let gcc_extensions c =
   { c with sizeof_void = Some 1; sizeof_fun = Some 1;
            alignof_void = Some 1; alignof_fun = Some 1 }
 
+(* Default configuration *)
+
 let config =
   ref (match Sys.word_size with
            | 32 -> ilp32ll64
diff --git a/cparser/Machine.mli b/cparser/Machine.mli
index bd3f357..f1d3567 100644
--- a/cparser/Machine.mli
+++ b/cparser/Machine.mli
@@ -39,13 +39,20 @@ type t = {
   alignof_double: int;
   alignof_longdouble: int;
   alignof_void: int option;
-  alignof_fun: int option
+  alignof_fun: int option;
+  bitfields_msb_first: bool
+
 }
 
 val ilp32ll64 : t
 val i32lpll64 : t
 val il32pll64 : t
-val make_char_signed : t -> t
+val x86_32 : t
+val x86_64 : t
+val win64 : t
+val ppc_32_bigendian : t
+val arm_littleendian : t
+
 val gcc_extensions : t -> t
 
 val config : t ref