1 files changed, 165 insertions, 40 deletions

diff --git a/gdb/m68k-tdep.c b/gdb/m68k-tdep.c
index 66f21fe..d0c4f0e 100644
--- a/gdb/m68k-tdep.c
+++ b/gdb/m68k-tdep.c
@@ -25,6 +25,7 @@
 #include "frame.h"
 #include "frame-base.h"
 #include "frame-unwind.h"
+#include "floatformat.h"
 #include "symtab.h"
 #include "gdbcore.h"
 #include "value.h"
@@ -129,8 +130,36 @@ m68k_register_name (int regnum)
     return register_names[regnum];
 }
 
-/* Extract from an array REGBUF containing the (raw) register state, a
-   function return value of TYPE, and copy that, in virtual format,
+/* There is a fair number of calling conventions that are in somewhat
+   wide use.  The 68000/08/10 don't support an FPU, not even as a
+   coprocessor.  All function return values are stored in %d0/%d1.
+   Structures are returned in a static buffer, a pointer to which is
+   returned in %d0.  This means that functions returning a structure
+   are not re-entrant.  To avoid this problem some systems use a
+   convention where the caller passes a pointer to a buffer in %a1
+   where the return values is to be stored.  This convention is the
+   default, and is implemented in the function m68k_return_value.
+
+   The 68020/030/040/060 do support an FPU, either as a coprocessor
+   (68881/2) or built-in (68040/68060).  That's why System V release 4
+   (SVR4) instroduces a new calling convention specified by the SVR4
+   psABI.  Integer values are returned in %d0/%d1, pointer return
+   values in %a0 and floating values in %fp0.  When calling functions
+   returning a structure the caller should pass a pointer to a buffer
+   for the return value in %a0.  This convention is implemented in the
+   function m68k_svr4_return_value, and by appropriately setting the
+   struct_value_regnum member of `struct gdbarch_tdep'.
+
+   GNU/Linux returns values in the same way as SVR4 does, but uses %a1
+   for passing the structure return value buffer.
+
+   GCC can also generate code where small structures are returned in
+   %d0/%d1 instead of in memory by using -freg-struct-return.  This is
+   the default on NetBSD a.out, OpenBSD and GNU/Linux and several
+   embedded systems.  This convention is implemented by setting the
+   struct_return member of `struct gdbarch_tdep' to reg_struct_return.  */
+
+/* Read a function return value of TYPE from REGCACHE, and copy that
    into VALBUF.  */
 
 static void
@@ -140,13 +169,6 @@ m68k_extract_return_value (struct type *type, struct regcache *regcache,
   int len = TYPE_LENGTH (type);
   char buf[M68K_MAX_REGISTER_SIZE];
 
-  if (TYPE_CODE (type) == TYPE_CODE_STRUCT
-      && TYPE_NFIELDS (type) == 1)
-    {
-      m68k_extract_return_value (TYPE_FIELD_TYPE (type, 0), regcache, valbuf);
-      return;
-    }
-
   if (len <= 4)
     {
       regcache_raw_read (regcache, M68K_D0_REGNUM, buf);
@@ -164,29 +186,39 @@ m68k_extract_return_value (struct type *type, struct regcache *regcache,
 		    "Cannot extract return value of %d bytes long.", len);
 }
 
-/* Write into the appropriate registers a function return value stored
-   in VALBUF of type TYPE, given in virtual format.  */
-
 static void
-m68k_store_return_value (struct type *type, struct regcache *regcache,
-			 const void *valbuf)
+m68k_svr4_extract_return_value (struct type *type, struct regcache *regcache,
+				void *valbuf)
 {
   int len = TYPE_LENGTH (type);
+  char buf[M68K_MAX_REGISTER_SIZE];
 
-  if (TYPE_CODE (type) == TYPE_CODE_STRUCT
-      && TYPE_NFIELDS (type) == 1)
+  if (TYPE_CODE (type) == TYPE_CODE_FLT)
     {
-      m68k_store_return_value (TYPE_FIELD_TYPE (type, 0), regcache, valbuf);
-      return;
+      regcache_raw_read (regcache, M68K_FP0_REGNUM, buf);
+      convert_typed_floating (buf, builtin_type_m68881_ext, valbuf, type);
     }
+  else if (TYPE_CODE (type) == TYPE_CODE_PTR && len == 4)
+    regcache_raw_read (regcache, M68K_A0_REGNUM, valbuf);
+  else
+    m68k_extract_return_value (type, regcache, valbuf);
+}
+
+/* Write a function return value of TYPE from VALBUF into REGCACHE.  */
+
+static void
+m68k_store_return_value (struct type *type, struct regcache *regcache,
+			 const void *valbuf)
+{
+  int len = TYPE_LENGTH (type);
 
   if (len <= 4)
     regcache_raw_write_part (regcache, M68K_D0_REGNUM, 4 - len, len, valbuf);
   else if (len <= 8)
     {
-      regcache_raw_write_part (regcache, M68K_D1_REGNUM, 8 - len,
+      regcache_raw_write_part (regcache, M68K_D0_REGNUM, 8 - len,
 			       len - 4, valbuf);
-      regcache_raw_write (regcache, M68K_D0_REGNUM,
+      regcache_raw_write (regcache, M68K_D1_REGNUM,
 			  (char *) valbuf + (len - 4));
     }
   else
@@ -194,29 +226,108 @@ m68k_store_return_value (struct type *type, struct regcache *regcache,
 		    "Cannot store return value of %d bytes long.", len);
 }
 
-/* Extract from REGCACHE, which contains the (raw) register state, the
-   address in which a function should return its structure value, as a
-   CORE_ADDR.  */
-
-static CORE_ADDR
-m68k_extract_struct_value_address (struct regcache *regcache)
+static void
+m68k_svr4_store_return_value (struct type *type, struct regcache *regcache,
+			      const void *valbuf)
 {
-  char buf[4];
+  int len = TYPE_LENGTH (type);
 
-  regcache_cooked_read (regcache, M68K_D0_REGNUM, buf);
-  return extract_unsigned_integer (buf, 4);
+  if (TYPE_CODE (type) == TYPE_CODE_FLT)
+    {
+      char buf[M68K_MAX_REGISTER_SIZE];
+      convert_typed_floating (valbuf, type, buf, builtin_type_m68881_ext);
+      regcache_raw_write (regcache, M68K_FP0_REGNUM, buf);
+    }
+  else if (TYPE_CODE (type) == TYPE_CODE_PTR && len == 4)
+    {
+      regcache_raw_write (regcache, M68K_A0_REGNUM, valbuf);
+      regcache_raw_write (regcache, M68K_D0_REGNUM, valbuf);
+    }
+  else
+    m68k_store_return_value (type, regcache, valbuf);
 }
 
+/* Return non-zero if TYPE, which is assumed to be a structure or
+   union type, should be returned in registers for architecture
+   GDBARCH.  */
+
 static int
-m68k_use_struct_convention (int gcc_p, struct type *type)
+m68k_reg_struct_return_p (struct gdbarch *gdbarch, struct type *type)
 {
-  enum struct_return struct_return;
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+  enum type_code code = TYPE_CODE (type);
+  int len = TYPE_LENGTH (type);
 
-  struct_return = gdbarch_tdep (current_gdbarch)->struct_return;
-  return generic_use_struct_convention (struct_return == reg_struct_return,
-					type);
+  gdb_assert (code == TYPE_CODE_STRUCT || code == TYPE_CODE_UNION);
+
+  if (tdep->struct_return == pcc_struct_return)
+    return 0;
+
+  return (len == 1 || len == 2 || len == 4 || len == 8);
 }
 
+/* Determine, for architecture GDBARCH, how a return value of TYPE
+   should be returned.  If it is supposed to be returned in registers,
+   and READBUF is non-zero, read the appropriate value from REGCACHE,
+   and copy it into READBUF.  If WRITEBUF is non-zero, write the value
+   from WRITEBUF into REGCACHE.  */
+
+static enum return_value_convention
+m68k_return_value (struct gdbarch *gdbarch, struct type *type,
+		   struct regcache *regcache, void *readbuf,
+		   const void *writebuf)
+{
+  enum type_code code = TYPE_CODE (type);
+
+  if ((code == TYPE_CODE_STRUCT || code == TYPE_CODE_UNION)
+      && !m68k_reg_struct_return_p (gdbarch, type))
+    return RETURN_VALUE_STRUCT_CONVENTION;
+
+  /* GCC returns a `long double' in memory.  */
+  if (code == TYPE_CODE_FLT && TYPE_LENGTH (type) == 12)
+    return RETURN_VALUE_STRUCT_CONVENTION;
+
+  if (readbuf)
+    m68k_extract_return_value (type, regcache, readbuf);
+  if (writebuf)
+    m68k_store_return_value (type, regcache, writebuf);
+
+  return RETURN_VALUE_REGISTER_CONVENTION;
+}
+
+static enum return_value_convention
+m68k_svr4_return_value (struct gdbarch *gdbarch, struct type *type,
+			struct regcache *regcache, void *readbuf,
+			const void *writebuf)
+{
+  enum type_code code = TYPE_CODE (type);
+
+  if ((code == TYPE_CODE_STRUCT || code == TYPE_CODE_UNION)
+      && !m68k_reg_struct_return_p (gdbarch, type))
+    return RETURN_VALUE_STRUCT_CONVENTION;
+
+  /* This special case is for structures consisting of a single
+     `float' or `double' member.  These structures are returned in
+     %fp0.  For these structures, we call ourselves recursively,
+     changing TYPE into the type of the first member of the structure.
+     Since that should work for all structures that have only one
+     member, we don't bother to check the member's type here.  */
+  if (code == TYPE_CODE_STRUCT && TYPE_NFIELDS (type) == 1)
+    {
+      type = check_typedef (TYPE_FIELD_TYPE (type, 0));
+      return m68k_svr4_return_value (gdbarch, type, regcache,
+				     readbuf, writebuf);
+    }
+
+  if (readbuf)
+    m68k_svr4_extract_return_value (type, regcache, readbuf);
+  if (writebuf)
+    m68k_svr4_store_return_value (type, regcache, writebuf);
+
+  return RETURN_VALUE_REGISTER_CONVENTION;
+}
+
+
 /* A function that tells us whether the function invocation represented
    by fi does not have a frame on the stack associated with it.  If it
    does not, FRAMELESS is set to 1, else 0.  */
@@ -293,6 +404,7 @@ m68k_push_dummy_call (struct gdbarch *gdbarch, CORE_ADDR func_addr,
 		      struct value **args, CORE_ADDR sp, int struct_return,
 		      CORE_ADDR struct_addr)
 {
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
   char buf[4];
   int i;
 
@@ -321,7 +433,7 @@ m68k_push_dummy_call (struct gdbarch *gdbarch, CORE_ADDR func_addr,
   if (struct_return)
     {
       store_unsigned_integer (buf, 4, struct_addr);
-      regcache_cooked_write (regcache, M68K_A1_REGNUM, buf);
+      regcache_cooked_write (regcache, tdep->struct_value_regnum, buf);
     }
 
   /* Store return address.  */
@@ -952,6 +1064,22 @@ m68k_get_longjmp_target (CORE_ADDR *pc)
   *pc = extract_unsigned_integer (buf, TARGET_PTR_BIT / TARGET_CHAR_BIT);
   return 1;
 }
+
+
+/* System V Release 4 (SVR4).  */
+
+void
+m68k_svr4_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
+{
+  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
+
+  /* SVR4 uses a different calling convention.  */
+  set_gdbarch_return_value (gdbarch, m68k_svr4_return_value);
+
+  /* SVR4 uses %a0 instead of %a1.  */
+  tdep->struct_value_regnum = M68K_A0_REGNUM;
+}
+
 
 /* Function: m68k_gdbarch_init
    Initializer function for the m68k gdbarch vector.
@@ -984,11 +1112,6 @@ m68k_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_believe_pcc_promotion (gdbarch, 1);
   set_gdbarch_decr_pc_after_break (gdbarch, 2);
 
-  set_gdbarch_extract_return_value (gdbarch, m68k_extract_return_value);
-  set_gdbarch_store_return_value (gdbarch, m68k_store_return_value);
-  set_gdbarch_deprecated_extract_struct_value_address (gdbarch, m68k_extract_struct_value_address);
-  set_gdbarch_use_struct_convention (gdbarch, m68k_use_struct_convention);
-
   set_gdbarch_deprecated_frameless_function_invocation (gdbarch, m68k_frameless_function_invocation);
   set_gdbarch_frame_args_skip (gdbarch, 8);
 
@@ -1002,6 +1125,7 @@ m68k_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
   set_gdbarch_fp0_regnum (gdbarch, M68K_FP0_REGNUM);
 
   set_gdbarch_push_dummy_call (gdbarch, m68k_push_dummy_call);
+  set_gdbarch_return_value (gdbarch, m68k_return_value);
 
   /* Disassembler.  */
   set_gdbarch_print_insn (gdbarch, print_insn_m68k);
@@ -1012,6 +1136,7 @@ m68k_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
 #else
   tdep->jb_pc = -1;
 #endif
+  tdep->struct_value_regnum = M68K_A1_REGNUM;
   tdep->struct_return = pcc_struct_return;
 
   /* Frame unwinder.  */