------- Comment #2 from rguenth at gcc dot gnu dot org 2009-11-19 16:49 -------
-ftree-vectorizer-verbose=2 tells you:
eval.f90:35: note: not vectorized: relevant stmt not supported: D.1684_73 =
((D.1683_72));
eval.f90:32: note: not vectorized: relevant stmt not supported: D.1684_58 =
((D.1683_57));
PAREN_EXPRs are new in 4.4 and I believe they cannot be turned off
right now.
The loops are
do i=1,nnd
x(i) = 1.d0 + (1.d0*i)/nnd
end do
do i=1,n
foo4(i) = 1.d0 + (1.d0*i)/n
end do
where the vectorizer doesn't know how to ensure evaluation order is
preserved when trying to vectorize (1.d0*i)/n. Writing them as
1.d0*i/n vectorizes the function.
Still the performance is lower by a factor of two compared to 4.3
(even with -ffast-math).
Probably the bug should be split.
--
rguenth at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |irar at il dot ibm dot com,
| |rguenth at gcc dot gnu dot
| |org
Severity|normal |enhancement
Status|UNCONFIRMED |NEW
Component|fortran |tree-optimization
Ever Confirmed|0 |1
Keywords| |missed-optimization
Last reconfirmed|0000-00-00 00:00:00 |2009-11-19 16:49:51
date| |
Summary|Performance drop from 4.3 to|[4.4/4.5 Regression]
|4.4/4.5 |Vectorizer cannot deal with
| |PAREN_EXPR gracefully, 50%
| |performance regression
Target Milestone|--- |4.4.3
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42108
