On Thu, Oct 20, 2011 at 4:45 PM, Joseph S. Myers
<jos...@codesourcery.com> wrote:
>> The patch was tested on x86_64-pc-linux-gnu, but I would like Joseph
>> to check if I didn't mess something with options handling.
>
> I have no comments on the option handling in this patch.
>
>> +for vectorized single float division and vectorized sqrtf(x) already with
>
> @code{sqrtf (@var{x})}
Thanks - fixed, with a similar fix in the previous paragraph.
I also found a PR that deals with vectorized reciprocal, so I referred
to the PR in the ChangeLog entry:
2011-10-20 Uros Bizjak <ubiz...@gmail.com>
PR target/47989
* config/i386/i386.h (RECIP_MASK_DEFAULT): New define.
* config/i386/i386.op (recip_mask): Initialize with RECIP_MASK_DEFAULT.
* doc/invoke.texi (ix86 Options, -mrecip): Document that GCC
implements vectorized single float division and vectorized sqrtf(x)
with reciprocal sequence with additional Newton-Raphson step with
-ffast-math.
Attached is the patch that was committed to mainline SVN. Encouraged
by Michael's results, let's see what automated benchmark testers will
show.
Uros.
Index: config/i386/i386.h
===================================================================
--- config/i386/i386.h (revision 180255)
+++ config/i386/i386.h (working copy)
@@ -2322,6 +2322,7 @@
#define RECIP_MASK_VEC_SQRT 0x08
#define RECIP_MASK_ALL (RECIP_MASK_DIV | RECIP_MASK_SQRT \
| RECIP_MASK_VEC_DIV | RECIP_MASK_VEC_SQRT)
+#define RECIP_MASK_DEFAULT (RECIP_MASK_VEC_DIV | RECIP_MASK_VEC_SQRT)
#define TARGET_RECIP_DIV ((recip_mask & RECIP_MASK_DIV) != 0)
#define TARGET_RECIP_SQRT ((recip_mask & RECIP_MASK_SQRT) != 0)
Index: config/i386/i386.opt
===================================================================
--- config/i386/i386.opt (revision 180255)
+++ config/i386/i386.opt (working copy)
@@ -32,7 +32,7 @@
HOST_WIDE_INT ix86_isa_flags_explicit
TargetVariable
-int recip_mask
+int recip_mask = RECIP_MASK_DEFAULT
Variable
int recip_mask_explicit
Index: doc/invoke.texi
===================================================================
--- doc/invoke.texi (revision 180255)
+++ doc/invoke.texi (working copy)
@@ -12922,7 +12922,12 @@
of the non-reciprocal instruction, the precision of the sequence can be
decreased by up to 2 ulp (i.e. the inverse of 1.0 equals 0.99999994).
-Note that GCC implements 1.0f/sqrtf(x) in terms of RSQRTSS (or RSQRTPS)
+Note that GCC implements @code{1.0f/sqrtf(@var{x})} in terms of RSQRTSS
+(or RSQRTPS) already with @option{-ffast-math} (or the above option
+combination), and doesn't need @option{-mrecip}.
+
+Also note that GCC emits the above sequence with additional Newton-Raphson step
+for vectorized single float division and vectorized @code{sqrtf(@var{x})}
already with @option{-ffast-math} (or the above option combination), and
doesn't need @option{-mrecip}.
