Hello!
This patch builds on recent patch by Michael (that implemented
fine-grained control on -mrecip option) and with -ffast-math emits
reciprocal sequences with additional NR step for vectorized SFmode
division and vectorized sqrtf(x).
2011-10-20 Uros Bizjak <ubiz...@gmail.com>
* config/i386/i386.h (RECIP_MASK_DEFAULT): New define.
* config/i386/i386.op (recip_mask): Initialize with RECIP_MASK_DEFAULT.
* doc/invoke.texi (mrecip): Document that GCC implements vectorized
single float division and vectorized sqrtf(x) with reciprocal sequence
with additional Newton-Raphson step with -ffast-math.
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.
The effect of the patch is 7% faster gas_dyn from polyhedron testsuite
on corei7-avx.
Uros.
Index: config/i386/i386.h
===================================================================
--- config/i386/i386.h (revision 180176)
+++ 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 180176)
+++ 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 180176)
+++ doc/invoke.texi (working copy)
@@ -12927,6 +12927,11 @@
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 sqrtf(x) already with
+@option{-ffast-math} (or the above option combination), and doesn't need
+@option{-mrecip}.
+
@item -mrecip=@var{opt}
@opindex mrecip=opt
This option allows to control which reciprocal estimate instructions
