Target FP: Add conversion routines to target-float.{c,h}

This patch adds the following conversion routines:
 - target_float_to_longest
 - target_float_from_longest
 - target_float_from_ulongest
 - target_float_convert
which call the equivalent decimal_ routines to handle decimal FP,
and call helper routines that currently still go via DOUBLEST to
handle binary FP.

The target_float_convert routine not only handles BFP<->BFP and
DFP<->DFP conversions, but also BFP<->DFP, which are implemented
by converting to a string and back.

These helpers are used in particular to implement conversion
from and to FP in value_cast, without going through DOUBLEST there.
In order to implement this for the FP<-integer case, the
pack_long / pack_unsigned_long routines are extended to support
floating-point values as output (thereby allowing use of
value_from_[u]longest with a floating-point target type).

This latter change also allows simplification of value_one.

gdb/ChangeLog:
2017-11-06  Ulrich Weigand  <uweigand@de.ibm.com>

	* target-float.c (floatformat_to_longest): New function.
	(floatformat_from_longest, floatformat_from_ulongest): Likewise.
	(floatformat_convert): Likewise.
	(target_float_to_longest): Likewise.
	(target_float_from_longest, target_float_from_ulongest): Likewise.
	(target_float_convert): Likewise.
	* target-float.h (target_float_to_longest): Add prototype.
	(target_float_from_longest, target_float_from_ulongest): Likewise.
	(target_float_convert): Likewise.

	* value.c (unpack_long): Use target_float_to_longest.
	(pack_long): Allow FP types.  Use target_float_from_longest.
	(pack_unsigned_long): Likewise using target_float_from_ulongest.
	* valops.c: Include "target-float.h".  Do not include "dfp.h".
	(value_cast): Handle conversions to FP using target_float_convert,
	value_from_ulongest, and value_from_longest.
	(value_one): Use value_from_longest for FP types as well.

1 files changed, 169 insertions, 0 deletions

diff --git a/gdb/target-float.c b/gdb/target-float.c
index e90cf037868..117892161f9 100644
--- a/gdb/target-float.c
+++ b/gdb/target-float.c
@@ -25,6 +25,64 @@
 #include "target-float.h"
 
 
+/* Helper routines operating on binary floating-point data.  */
+
+/* Convert the byte-stream ADDR, interpreted as floating-point format FMT,
+   to an integer value (rounding towards zero).  */
+static LONGEST
+floatformat_to_longest (const struct floatformat *fmt, const gdb_byte *addr)
+{
+  DOUBLEST d;
+  floatformat_to_doublest (fmt, addr, &d);
+  return (LONGEST) d;
+}
+
+/* Convert signed integer VAL to a target floating-number of format FMT
+   and store it as byte-stream ADDR.  */
+static void
+floatformat_from_longest (const struct floatformat *fmt, gdb_byte *addr,
+			  LONGEST val)
+{
+  DOUBLEST d = (DOUBLEST) val;
+  floatformat_from_doublest (fmt, &d, addr);
+}
+
+/* Convert unsigned integer VAL to a target floating-number of format FMT
+   and store it as byte-stream ADDR.  */
+static void
+floatformat_from_ulongest (const struct floatformat *fmt, gdb_byte *addr,
+			   ULONGEST val)
+{
+  DOUBLEST d = (DOUBLEST) val;
+  floatformat_from_doublest (fmt, &d, addr);
+}
+
+/* Convert a floating-point number of format FROM_FMT from the target
+   byte-stream FROM to a floating-point number of format TO_FMT, and
+   store it to the target byte-stream TO.  */
+static void
+floatformat_convert (const gdb_byte *from, const struct floatformat *from_fmt,
+		     gdb_byte *to, const struct floatformat *to_fmt)
+{
+  if (from_fmt == to_fmt)
+    {
+      /* The floating-point formats match, so we simply copy the data.  */
+      memcpy (to, from, floatformat_totalsize_bytes (to_fmt));
+    }
+  else
+    {
+      /* The floating-point formats don't match.  The best we can do
+	 (apart from simulating the target FPU) is converting to the
+	 widest floating-point type supported by the host, and then
+	 again to the desired type.  */
+      DOUBLEST d;
+
+      floatformat_to_doublest (from_fmt, from, &d);
+      floatformat_from_doublest (to_fmt, &d, to);
+    }
+}
+
+
 /* Typed floating-point routines.  These routines operate on floating-point
    values in target format, represented by a byte buffer interpreted as a
    "struct type", which may be either a binary or decimal floating-point
@@ -97,3 +155,114 @@ target_float_from_string (gdb_byte *addr, const struct type *type,
 
   gdb_assert_not_reached ("unexpected type code");
 }
+
+/* Convert the byte-stream ADDR, interpreted as floating-point type TYPE,
+   to an integer value (rounding towards zero).  */
+LONGEST
+target_float_to_longest (const gdb_byte *addr, const struct type *type)
+{
+  if (TYPE_CODE (type) == TYPE_CODE_FLT)
+    return floatformat_to_longest (floatformat_from_type (type), addr);
+
+  if (TYPE_CODE (type) == TYPE_CODE_DECFLOAT)
+    return decimal_to_longest (addr, TYPE_LENGTH (type),
+			       gdbarch_byte_order (get_type_arch (type)));
+
+  gdb_assert_not_reached ("unexpected type code");
+}
+
+/* Convert signed integer VAL to a target floating-number of type TYPE
+   and store it as byte-stream ADDR.  */
+void
+target_float_from_longest (gdb_byte *addr, const struct type *type,
+			   LONGEST val)
+{
+  /* Ensure possible padding bytes in the target buffer are zeroed out.  */
+  memset (addr, 0, TYPE_LENGTH (type));
+
+  if (TYPE_CODE (type) == TYPE_CODE_FLT)
+    {
+      floatformat_from_longest (floatformat_from_type (type), addr, val);
+      return;
+    }
+
+  if (TYPE_CODE (type) == TYPE_CODE_DECFLOAT)
+    {
+      decimal_from_longest (val, addr, TYPE_LENGTH (type),
+			    gdbarch_byte_order (get_type_arch (type)));
+      return;
+    }
+
+  gdb_assert_not_reached ("unexpected type code");
+}
+
+/* Convert unsigned integer VAL to a target floating-number of type TYPE
+   and store it as byte-stream ADDR.  */
+void
+target_float_from_ulongest (gdb_byte *addr, const struct type *type,
+			    ULONGEST val)
+{
+  /* Ensure possible padding bytes in the target buffer are zeroed out.  */
+  memset (addr, 0, TYPE_LENGTH (type));
+
+  if (TYPE_CODE (type) == TYPE_CODE_FLT)
+    {
+      floatformat_from_ulongest (floatformat_from_type (type), addr, val);
+      return;
+    }
+
+  if (TYPE_CODE (type) == TYPE_CODE_DECFLOAT)
+    {
+      decimal_from_ulongest (val, addr, TYPE_LENGTH (type),
+			     gdbarch_byte_order (get_type_arch (type)));
+      return;
+    }
+
+  gdb_assert_not_reached ("unexpected type code");
+}
+
+/* Convert a floating-point number of type FROM_TYPE from the target
+   byte-stream FROM to a floating-point number of type TO_TYPE, and
+   store it to the target byte-stream TO.  */
+void
+target_float_convert (const gdb_byte *from, const struct type *from_type,
+		      gdb_byte *to, const struct type *to_type)
+{
+  /* Ensure possible padding bytes in the target buffer are zeroed out.  */
+  memset (to, 0, TYPE_LENGTH (to_type));
+
+  /* Use direct conversion routines if we have them.  */
+
+  if (TYPE_CODE (from_type) == TYPE_CODE_FLT
+      && TYPE_CODE (to_type) == TYPE_CODE_FLT)
+    {
+      floatformat_convert (from, floatformat_from_type (from_type),
+			   to, floatformat_from_type (to_type));
+      return;
+    }
+
+  if (TYPE_CODE (from_type) == TYPE_CODE_DECFLOAT
+      && TYPE_CODE (to_type) == TYPE_CODE_DECFLOAT)
+    {
+      decimal_convert (from, TYPE_LENGTH (from_type),
+		       gdbarch_byte_order (get_type_arch (from_type)),
+		       to, TYPE_LENGTH (to_type),
+		       gdbarch_byte_order (get_type_arch (to_type)));
+      return;
+    }
+
+  /* We cannot directly convert between binary and decimal floating-point
+     types, so go via an intermediary string.  */
+
+  if ((TYPE_CODE (from_type) == TYPE_CODE_FLT
+       && TYPE_CODE (to_type) == TYPE_CODE_DECFLOAT)
+      || (TYPE_CODE (from_type) == TYPE_CODE_DECFLOAT
+	  && TYPE_CODE (to_type) == TYPE_CODE_FLT))
+    {
+      std::string str = target_float_to_string (from, from_type);
+      target_float_from_string (to, to_type, str);
+      return;
+    }
+
+  gdb_assert_not_reached ("unexpected type code");
+}