One of my patches for PR48866 mysteriously regressed fma3-fma.c. It
turned out that a rearrangement in the order of emitting insns during
expansion caused combine to attempt combinations in a different order,
and this ended up exposing a latent error in the cost computation of FMA
insns, that caused a desirable combination to be regarded as not
profitable. The problem was that, when stripping out NEGs from
operands, that would be costless in FMA variants, we took the
sub-operand from the wrong variable. Oops.
I took the opportunity to fix the names of the fma_fnm* patterns, that
were missing the “n”.
Regstrapped on x86_64-linux-gnu and i686-linux-gnu. Ok to install?
for gcc/ChangeLog
from Alexandre Oliva <aol...@redhat.com>
* config/i386/i386.c (ix86_rtx_costs): Drop NEG from sub for FMA.
* config/i386/sse.md: Add n to negated FMA pattern names.
Index: gcc/config/i386/i386.c
===================================================================
--- gcc/config/i386/i386.c.orig 2011-05-26 05:03:11.755995482 -0300
+++ gcc/config/i386/i386.c 2011-05-26 05:03:20.639013123 -0300
@@ -29231,12 +29231,12 @@ ix86_rtx_costs (rtx x, int code, int out
/* Negate in op0 or op2 is free: FMS, FNMA, FNMS. */
sub = XEXP (x, 0);
if (GET_CODE (sub) == NEG)
- sub = XEXP (x, 0);
+ sub = XEXP (sub, 0);
*total += rtx_cost (sub, FMA, speed);
sub = XEXP (x, 2);
if (GET_CODE (sub) == NEG)
- sub = XEXP (x, 0);
+ sub = XEXP (sub, 0);
*total += rtx_cost (sub, FMA, speed);
return true;
}
Index: gcc/config/i386/sse.md
===================================================================
--- gcc/config/i386/sse.md.orig 2011-05-26 05:03:11.755995482 -0300
+++ gcc/config/i386/sse.md 2011-05-26 05:03:20.642013129 -0300
@@ -1731,7 +1731,7 @@
[(set_attr "type" "ssemuladd")
(set_attr "mode" "<MODE>")])
-(define_insn "*fma_fmadd_<mode>"
+(define_insn "*fma_fnmadd_<mode>"
[(set (match_operand:FMAMODE 0 "register_operand" "=x,x,x")
(fma:FMAMODE
(neg:FMAMODE
@@ -1746,7 +1746,7 @@
[(set_attr "type" "ssemuladd")
(set_attr "mode" "<MODE>")])
-(define_insn "*fma_fmsub_<mode>"
+(define_insn "*fma_fnmsub_<mode>"
[(set (match_operand:FMAMODE 0 "register_operand" "=x,x,x")
(fma:FMAMODE
(neg:FMAMODE
--
Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/ FSF Latin America board member
Free Software Evangelist Red Hat Brazil Compiler Engineer
