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[rfc] Tighten meaning of gdbarch_convert_register_p


This patch tightens the definition of gdbarch_convert_register_p so
that a non-zero result means that a conversion is necessary for the
supplied TYPE, not just that one might be necessary for some type.
This let me add an assertion that gdbarch_register_convert_p was
zero for any unwound register values in the new value-based unwinding
that I wrote yesterday.

It doesn't affect anything besides the assertion, since all
definitions do no-op conversions to the register's own type anyway.
We could document that requirement on gdbarch_register_to_value and
gdbarch_value_to_register instead and drop the assertion if you
don't think this patch is appropriate.  It seems abstractly right,
though - if we do not need a conversion, don't call the conversion
functions.

What do you think?

Tested on x86_64-linux.

-- 
Daniel Jacobowitz
CodeSourcery

2007-10-17  Daniel Jacobowitz  <dan@codesourcery.com>

	* amd64-tdep.c (amd64_convert_register_p): Delete.
	(amd64_init_abi): Use i387_convert_register_p.
	* alpha-tdep.c (alpha_convert_register_p): Return zero for
	eight byte types.
	(alpha_register_to_value, alpha_value_to_register): Do not handle
	eight byte types.
	* i386-tdep.c (i386_convert_register_p): Use i387_convert_register_p.
	* i387-tdep.c (i387_convert_register_p): New.
	(i387_register_to_value, i387_value_to_register): Update comments.
	* i387-tdep.h (i387_convert_register_p): Declare.
	* ia64-tdep.c (ia64_convert_register_p): Return zero for
	builtin_type_ia64_ext.
	(ia64_gdbarch_init): Do not initialize builtin_type_ia64_ext here.
	(_initialize_ia64_tdep): Initialize builtin_type_ia64_ext here.
	* m68k-tdep.c (m68k_convert_register_p): Return zero for
	builtin_type_m68881_ext.
	(m68k_register_to_value, m68k_value_to_register): Update comments.

	* gdbint.texinfo (Register and Memory Data, Target Conditionals):
	Document that gdbarch_convert_register_p should return zero for no-op
	conversions.

---
 gdb/alpha-tdep.c       |    9 ++-------
 gdb/amd64-tdep.c       |   10 +---------
 gdb/doc/gdbint.texinfo |    7 +++++--
 gdb/i386-tdep.c        |    2 +-
 gdb/i387-tdep.c        |   25 +++++++++++++++++++++----
 gdb/i387-tdep.h        |    5 +++++
 gdb/ia64-tdep.c        |   15 ++++++++-------
 gdb/m68k-tdep.c        |    9 ++++-----
 8 files changed, 47 insertions(+), 35 deletions(-)

Index: src/gdb/amd64-tdep.c
===================================================================
--- src.orig/gdb/amd64-tdep.c	2007-10-17 09:24:11.000000000 -0400
+++ src/gdb/amd64-tdep.c	2007-10-17 09:43:53.000000000 -0400
@@ -200,14 +200,6 @@ amd64_dwarf_reg_to_regnum (int reg)
   return regnum;
 }
 
-/* Return nonzero if a value of type TYPE stored in register REGNUM
-   needs any special handling.  */
-
-static int
-amd64_convert_register_p (int regnum, struct type *type)
-{
-  return i386_fp_regnum_p (regnum);
-}
 
 
 /* Register classes as defined in the psABI.  */
@@ -1155,7 +1147,7 @@ amd64_init_abi (struct gdbarch_info info
   set_gdbarch_frame_align (gdbarch, amd64_frame_align);
   set_gdbarch_frame_red_zone_size (gdbarch, 128);
 
-  set_gdbarch_convert_register_p (gdbarch, amd64_convert_register_p);
+  set_gdbarch_convert_register_p (gdbarch, i387_convert_register_p);
   set_gdbarch_register_to_value (gdbarch, i387_register_to_value);
   set_gdbarch_value_to_register (gdbarch, i387_value_to_register);
 
Index: src/gdb/alpha-tdep.c
===================================================================
--- src.orig/gdb/alpha-tdep.c	2007-10-17 09:44:48.000000000 -0400
+++ src/gdb/alpha-tdep.c	2007-10-17 09:45:39.000000000 -0400
@@ -200,7 +200,8 @@ alpha_sts (void *out, const void *in)
 static int
 alpha_convert_register_p (int regno, struct type *type)
 {
-  return (regno >= ALPHA_FP0_REGNUM && regno < ALPHA_FP0_REGNUM + 31);
+  return (regno >= ALPHA_FP0_REGNUM && regno < ALPHA_FP0_REGNUM + 31
+	  && TYPE_LENGTH (type) != 8);
 }
 
 static void
@@ -215,9 +216,6 @@ alpha_register_to_value (struct frame_in
     case 4:
       alpha_sts (out, in);
       break;
-    case 8:
-      memcpy (out, in, 8);
-      break;
     default:
       error (_("Cannot retrieve value from floating point register"));
     }
@@ -234,9 +232,6 @@ alpha_value_to_register (struct frame_in
     case 4:
       alpha_lds (out, in);
       break;
-    case 8:
-      memcpy (out, in, 8);
-      break;
     default:
       error (_("Cannot store value in floating point register"));
     }
Index: src/gdb/i386-tdep.c
===================================================================
--- src.orig/gdb/i386-tdep.c	2007-10-17 09:42:50.000000000 -0400
+++ src/gdb/i386-tdep.c	2007-10-17 09:43:23.000000000 -0400
@@ -1880,7 +1880,7 @@ i386_convert_register_p (int regnum, str
 	return 1;
     }
 
-  return i386_fp_regnum_p (regnum);
+  return i387_convert_register_p (regnum, type);
 }
 
 /* Read a value of type TYPE from register REGNUM in frame FRAME, and
Index: src/gdb/i387-tdep.c
===================================================================
--- src.orig/gdb/i387-tdep.c	2007-10-17 09:39:14.000000000 -0400
+++ src/gdb/i387-tdep.c	2007-10-17 09:42:16.000000000 -0400
@@ -285,6 +285,25 @@ i387_print_float_info (struct gdbarch *g
 }
 
 
+/* Return nonzero if a value of type TYPE stored in register REGNUM
+   needs any special handling.  */
+
+int
+i387_convert_register_p (int regnum, struct type *type)
+{
+  if (i386_fp_regnum_p (regnum))
+    {
+      /* Floating point registers must be converted unless we are
+	 accessing them in their hardware type.  */
+      if (type == builtin_type_i387_ext)
+	return 0;
+      else
+	return 1;
+    }
+
+  return 0;
+}
+
 /* Read a value of type TYPE from register REGNUM in frame FRAME, and
    return its contents in TO.  */
 
@@ -304,8 +323,7 @@ i387_register_to_value (struct frame_inf
       return;
     }
 
-  /* Convert to TYPE.  This should be a no-op if TYPE is equivalent to
-     the extended floating-point format used by the FPU.  */
+  /* Convert to TYPE.  */
   get_frame_register (frame, regnum, from);
   convert_typed_floating (from, builtin_type_i387_ext, to, type);
 }
@@ -329,8 +347,7 @@ i387_value_to_register (struct frame_inf
       return;
     }
 
-  /* Convert from TYPE.  This should be a no-op if TYPE is equivalent
-     to the extended floating-point format used by the FPU.  */
+  /* Convert from TYPE.  */
   convert_typed_floating (from, type, to, builtin_type_i387_ext);
   put_frame_register (frame, regnum, to);
 }
Index: src/gdb/i387-tdep.h
===================================================================
--- src.orig/gdb/i387-tdep.h	2007-10-17 09:41:49.000000000 -0400
+++ src/gdb/i387-tdep.h	2007-10-17 09:41:55.000000000 -0400
@@ -55,6 +55,11 @@ extern void i387_print_float_info (struc
 				   struct frame_info *frame,
 				   const char *args);
 
+/* Return nonzero if a value of type TYPE stored in register REGNUM
+   needs any special handling.  */
+
+extern int i387_convert_register_p (int regnum, struct type *type);
+
 /* Read a value of type TYPE from register REGNUM in frame FRAME, and
    return its contents in TO.  */
 
Index: src/gdb/ia64-tdep.c
===================================================================
--- src.orig/gdb/ia64-tdep.c	2007-10-17 09:46:44.000000000 -0400
+++ src/gdb/ia64-tdep.c	2007-10-17 09:48:16.000000000 -0400
@@ -920,7 +920,8 @@ ia64_pseudo_register_write (struct gdbar
 static int
 ia64_convert_register_p (int regno, struct type *type)
 {
-  return (regno >= IA64_FR0_REGNUM && regno <= IA64_FR127_REGNUM);
+  return (regno >= IA64_FR0_REGNUM && regno <= IA64_FR127_REGNUM
+	  && type != builtin_type_ia64_ext);
 }
 
 static void
@@ -3564,12 +3565,6 @@ ia64_gdbarch_init (struct gdbarch_info i
   tdep->sigcontext_register_address = 0;
   tdep->pc_in_sigtramp = 0;
 
-  /* Define the ia64 floating-point format to gdb.  */
-  builtin_type_ia64_ext =
-    init_type (TYPE_CODE_FLT, 128 / 8,
-               0, "builtin_type_ia64_ext", NULL);
-  TYPE_FLOATFORMAT (builtin_type_ia64_ext) = floatformats_ia64_ext;
-
   /* According to the ia64 specs, instructions that store long double
      floats in memory use a long-double format different than that
      used in the floating registers.  The memory format matches the
@@ -3652,5 +3647,11 @@ extern initialize_file_ftype _initialize
 void
 _initialize_ia64_tdep (void)
 {
+  /* Define the ia64 floating-point format to gdb.  */
+  builtin_type_ia64_ext =
+    init_type (TYPE_CODE_FLT, 128 / 8,
+               0, "builtin_type_ia64_ext", NULL);
+  TYPE_FLOATFORMAT (builtin_type_ia64_ext) = floatformats_ia64_ext;
+
   gdbarch_register (bfd_arch_ia64, ia64_gdbarch_init, NULL);
 }
Index: src/gdb/m68k-tdep.c
===================================================================
--- src.orig/gdb/m68k-tdep.c	2007-10-17 09:49:27.000000000 -0400
+++ src/gdb/m68k-tdep.c	2007-10-17 09:50:04.000000000 -0400
@@ -171,7 +171,8 @@ m68k_convert_register_p (int regnum, str
 {
   if (!gdbarch_tdep (current_gdbarch)->fpregs_present)
     return 0;
-  return (regnum >= M68K_FP0_REGNUM && regnum <= M68K_FP0_REGNUM + 7);
+  return (regnum >= M68K_FP0_REGNUM && regnum <= M68K_FP0_REGNUM + 7
+	  && type != builtin_type_m68881_ext);
 }
 
 /* Read a value of type TYPE from register REGNUM in frame FRAME, and
@@ -193,8 +194,7 @@ m68k_register_to_value (struct frame_inf
       return;
     }
 
-  /* Convert to TYPE.  This should be a no-op if TYPE is equivalent to
-     the extended floating-point format used by the FPU.  */
+  /* Convert to TYPE.  */
   get_frame_register (frame, regnum, from);
   convert_typed_floating (from, fpreg_type, to, type);
 }
@@ -218,8 +218,7 @@ m68k_value_to_register (struct frame_inf
       return;
     }
 
-  /* Convert from TYPE.  This should be a no-op if TYPE is equivalent
-     to the extended floating-point format used by the FPU.  */
+  /* Convert from TYPE.  */
   convert_typed_floating (from, type, to, fpreg_type);
   put_frame_register (frame, regnum, to);
 }
Index: src/gdb/doc/gdbint.texinfo
===================================================================
--- src.orig/gdb/doc/gdbint.texinfo	2007-10-17 09:51:43.000000000 -0400
+++ src/gdb/doc/gdbint.texinfo	2007-10-17 09:53:30.000000000 -0400
@@ -3226,6 +3226,9 @@ when stored in memory.
 
 When non-zero, the macros @code{gdbarch_register_to_value} and
 @code{value_to_register} are used to perform any necessary conversion.
+
+This function should return zero for the register's native type, when
+no conversion is necessary.
 @end deftypefun
 
 @deftypefun void gdbarch_register_to_value (struct gdbarch *@var{gdbarch}, int @var{reg}, struct type *@var{type}, char *@var{from}, char *@var{to})
@@ -3462,8 +3465,8 @@ default so that @value{GDBN} will assume
 
 @item int gdbarch_convert_register_p (@var{gdbarch}, @var{regnum}, struct type *@var{type})
 @findex gdbarch_convert_register_p
-Return non-zero if register @var{regnum} can represent data values in a
-non-standard form.
+Return non-zero if register @var{regnum} represents data values of type
+@var{type} in a non-standard form.
 @xref{Target Architecture Definition, , Using Different Register and Memory Data Representations}.
 
 @item CORE_ADDR gdbarch_decr_pc_after_break (@var{gdbarch})


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