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Fix for ?Fmode descriptions on non-8-bit-byte machines.
- To: gcc-patches at gcc dot gnu dot org
- Subject: Fix for ?Fmode descriptions on non-8-bit-byte machines.
- From: Geoffrey Keating <geoffk at thief dot cygnus dot com>
- Date: Tue, 19 Jun 2001 11:10:37 -0700
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