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Fix for ?Fmode descriptions on non-8-bit-byte machines.



While discussing a previous patch, some people were confused by the
slightly inaccurate documentaton of the floating point modes.

On some machines, it is contradictory to be 4-byte and
single-precision, for instance.

Of course, what we really want is that SFmode is the same size as
SImode; on machines with 16-bit bytes, this means that the
single-precision mode is HFmode.

-- 
Geoff Keating <geoffk@redhat.com>

2001-06-19  Geoffrey Keating  <geoffk@redhat.com>

	* doc/rtl.texi (Machine Modes): Correct description of
	floating-point modes on machines with non-8-bit bytes.

cvs server: Diffing doc
Index: doc/rtl.texi
===================================================================
RCS file: /cvs/gcc/gcc/gcc/doc/rtl.texi,v
retrieving revision 1.5
diff -p -u -p -r1.5 rtl.texi
--- rtl.texi	2001/06/14 22:51:18	1.5
+++ rtl.texi	2001/06/19 18:02:13
@@ -734,25 +734,29 @@ this is the right mode to use for certai
 
 @findex SFmode
 @item SFmode
-``Single Floating'' mode represents a single-precision (four byte) floating
-point number.
+``Single Floating'' mode represents a four byte floating point number.
+In the common case, of a processor with IEEE arithmetic and 8-bit bytes,
+this is a single-precision IEEE floating point number; it can also be
+used for double-precision (on processors with 16-bit bytes) and
+single-precision Vax types.
 
 @findex DFmode
 @item DFmode
-``Double Floating'' mode represents a double-precision (eight byte) floating
-point number.
+``Double Floating'' mode represents an eight byte floating point number.
+In the common case, of a processor with IEEE arithmetic and 8-bit bytes,
+this is a double-precision IEEE floating point number.
 
 @findex XFmode
 @item XFmode
-``Extended Floating'' mode represents a triple-precision (twelve byte)
-floating point number.  This mode is used for IEEE extended floating
-point.  On some systems not all bits within these bytes will actually
-be used.
+``Extended Floating'' mode represents a twelve byte floating point
+number.  This mode is used for IEEE extended floating point.  On some
+systems not all bits within these bytes will actually be used.
 
 @findex TFmode
 @item TFmode
-``Tetra Floating'' mode represents a quadruple-precision (sixteen byte)
-floating point number.
+``Tetra Floating'' mode represents a sixteen byte floating point number.
+This gets used for both the 96-bit extended IEEE floating-point types
+padded to 128 bits, and true 128-bit extended IEEE floating-point types.
 
 @findex CCmode
 @item CCmode


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