[RFC] Detecting and printing 128-bit long double values for PPC

[Luis Machado <luisgpm@linux.vnet.ibm.com>]

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Hi,

Follows attached the patch for detecting and printing 128-bit long
double values on GDB for PPC. 

This patch was originally written by Pete Carr some time ago. Since its
discussion didn't go much further, i've refreshed it to cleanly apply on
HEAD. The original message with the patch can be found here:
(http://sourceware.org/ml/gdb-patches/2006-07/msg00098.html)

I've modified some bits and pieces suggested by  Mark Kettenis and
Daniel Jacobowitz on these mailing list entries.

http://sourceware.org/ml/gdb-patches/2006-07/msg00103.html
http://sourceware.org/ml/gdb-patches/2006-07/msg00107.html


Comments are welcome.

Best regards,
Luis

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2007-04-26  Pete Carr  <pecarr@us.ibm.com>
						Luis Machado  <luisgpm@br.ibm.com>

	* rs6000-tdep.c (rs6000_gdbarch_init): Set the long double format for
	powerpc64.
	* configure.host : Set the host long double format for powerpc64 to be
	a 128-bit type defined in libiberty/floatformat.c.
	* ppc-linux-tdep.c (ppc_linux_init_abi): Remove code that sets long double 
	size to 8 bytes.
	* floatformat.c : Introduce default floatformat structs to describe the
	128-bit long double found on the powerpc64. Description does not fully
	describe this format which is actually a pair of 64-bit doubles. However
	we are relying on floatformat_to_doublest() recognizing that this is
	also the default host floatformat.
	* floatformat.h : Default floatformat structs for powerpc64 128-bit
	long doubles.
	* gdbtypes.h : Added new type struct floatformats_ppc64_long_double 
	declaration
	* gdbtypes.c : Added new type struct floatformats_ppc64_long_double

Index: gdb/configure.host
===================================================================
--- gdb/configure.host.orig	2007-04-27 21:05:28.000000000 -0700
+++ gdb/configure.host	2007-04-27 21:05:32.000000000 -0700
@@ -198,6 +198,11 @@
 	gdb_host_double_format="&floatformat_ieee_double_big"
 	gdb_host_long_double_format="&floatformat_m68881_ext"
 	;;
+powerpc64-*-*)
+	gdb_host_float_format=0
+	gdb_host_double_format=0
+	gdb_host_long_double_format="&floatformat_ppc64_long_double_big"
+	;;
 *)
 	gdb_host_float_format=0
 	gdb_host_double_format=0
Index: gdb/ppc-linux-tdep.c
===================================================================
--- gdb/ppc-linux-tdep.c.orig	2007-04-27 21:05:28.000000000 -0700
+++ gdb/ppc-linux-tdep.c	2007-04-27 21:12:29.000000000 -0700
@@ -1028,16 +1028,6 @@
 {
   struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);
 
-  /* NOTE: jimb/2004-03-26: The System V ABI PowerPC Processor
-     Supplement says that long doubles are sixteen bytes long.
-     However, as one of the known warts of its ABI, PPC GNU/Linux uses
-     eight-byte long doubles.  GCC only recently got 128-bit long
-     double support on PPC, so it may be changing soon.  The
-     Linux[sic] Standards Base says that programs that use 'long
-     double' on PPC GNU/Linux are non-conformant.  */
-  /* NOTE: cagney/2005-01-25: True for both 32- and 64-bit.  */
-  set_gdbarch_long_double_bit (gdbarch, 8 * TARGET_CHAR_BIT);
-
   if (tdep->wordsize == 4)
     {
       /* Until November 2001, gcc did not comply with the 32 bit SysV
Index: gdb/rs6000-tdep.c
===================================================================
--- gdb/rs6000-tdep.c.orig	2007-04-27 21:05:28.000000000 -0700
+++ gdb/rs6000-tdep.c	2007-04-27 21:05:32.000000000 -0700
@@ -3425,7 +3425,13 @@
   set_gdbarch_float_bit (gdbarch, 4 * TARGET_CHAR_BIT);
   set_gdbarch_double_bit (gdbarch, 8 * TARGET_CHAR_BIT);
   if (sysv_abi)
-    set_gdbarch_long_double_bit (gdbarch, 16 * TARGET_CHAR_BIT);
+    {
+      int byte_order = gdbarch_byte_order (gdbarch);
+
+      set_gdbarch_long_double_format(gdbarch, floatformats_ppc64_long_double);
+      
+      set_gdbarch_long_double_bit (gdbarch, 16 * TARGET_CHAR_BIT);
+    }
   else
     set_gdbarch_long_double_bit (gdbarch, 8 * TARGET_CHAR_BIT);
   set_gdbarch_char_signed (gdbarch, 0);
Index: include/floatformat.h
===================================================================
--- include/floatformat.h.orig	2007-04-27 21:05:28.000000000 -0700
+++ include/floatformat.h	2007-04-27 21:05:32.000000000 -0700
@@ -118,6 +118,9 @@
 extern const struct floatformat floatformat_ia64_spill_little;
 extern const struct floatformat floatformat_ia64_quad_big;
 extern const struct floatformat floatformat_ia64_quad_little;
+/* ppc64 long double implemented as 2 doubles */
+extern const struct floatformat floatformat_ppc64_long_double_big;
+extern const struct floatformat floatformat_ppc64_long_double_little;
 
 /* Convert from FMT to a double.
    FROM is the address of the extended float.
Index: libiberty/floatformat.c
===================================================================
--- libiberty/floatformat.c.orig	2007-04-27 21:05:28.000000000 -0700
+++ libiberty/floatformat.c	2007-04-27 21:05:32.000000000 -0700
@@ -106,6 +106,25 @@
   floatformat_always_valid
 };
 
+/* floatformats for ppc64 long double, big and little endian.
+		The layout is a pair of doubles. Don't use this description to pass
+		information to get_field(). The bit size is the important thing. */
+const struct floatformat floatformat_ppc64_long_double_big =
+{
+  floatformat_big, 128, 0, 1, 11, 1023, 2047, 12, 52, 
+  floatformat_intbit_no,
+  "floatformat_ppc64_long_double_big",
+  floatformat_always_valid
+};
+
+const struct floatformat floatformat_ppc64_long_double_little =
+{
+  floatformat_little, 128, 0, 1, 11, 1023, 2047, 12, 52, 
+  floatformat_intbit_no,
+  "floatformat_ppc64_long_double_little",
+  floatformat_always_valid
+};
+
 /* floatformat for IEEE double, little endian byte order, with big endian word
    ordering, as on the ARM.  */
 
Index: gdb/gdbtypes.c
===================================================================
--- gdb/gdbtypes.c.orig	2007-04-27 21:05:28.000000000 -0700
+++ gdb/gdbtypes.c	2007-04-27 21:06:00.000000000 -0700
@@ -112,6 +112,11 @@
   &floatformat_ieee_double_big,
   &floatformat_ieee_double_littlebyte_bigword
 };
+const struct floatformat *floatformats_ppc64_long_double[BFD_ENDIAN_UNKNOWN] =
+{
+  &floatformat_ppc64_long_double_big,
+  &floatformat_ppc64_long_double_little
+};
 const struct floatformat *floatformats_i387_ext[BFD_ENDIAN_UNKNOWN] = {
   &floatformat_i387_ext,
   &floatformat_i387_ext
Index: gdb/gdbtypes.h
===================================================================
--- gdb/gdbtypes.h.orig	2007-04-27 21:05:28.000000000 -0700
+++ gdb/gdbtypes.h	2007-04-27 21:05:32.000000000 -0700
@@ -1118,6 +1118,7 @@
 extern const struct floatformat *floatformats_ieee_single[BFD_ENDIAN_UNKNOWN];
 extern const struct floatformat *floatformats_ieee_double[BFD_ENDIAN_UNKNOWN];
 extern const struct floatformat *floatformats_ieee_double_littlebyte_bigword[BFD_ENDIAN_UNKNOWN];
+extern const struct floatformat *floatformats_ppc64_long_double[BFD_ENDIAN_UNKNOWN];
 extern const struct floatformat *floatformats_i387_ext[BFD_ENDIAN_UNKNOWN];
 extern const struct floatformat *floatformats_m68881_ext[BFD_ENDIAN_UNKNOWN];
 extern const struct floatformat *floatformats_arm_ext[BFD_ENDIAN_UNKNOWN];