http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47092
Summary: [4.6 Regression]
gfortran.fortran-torture/execute/forall_4.f90 is VERY
slow with -fgraphite-identity
Product: gcc
Version: 4.6.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: middle-end
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: zso...@seznam.cz
CC: s...@gcc.gnu.org
Host: x86_64-pc-linux-gnu
Target: x86_64-pc-linux-gnu
$ gfortran-4.4.5 -O -fgraphite-identity forall_4.f90
$ time ./a.out
real 0m0.002s
user 0m0.000s
sys 0m0.000s
$ gfortran-4.5.2 -O -fgraphite-identity forall_4.f90
$ time ./a.out
real 0m0.002s
user 0m0.000s
sys 0m0.000s
$ gfortran -O -fgraphite-identity forall_4.f90
$ time ./a.out
real 0m26.461s
user 0m26.290s
sys 0m0.050s
The problem seems to be this empty loop:
.L24:
mov rax, rdx # D.1888, D.1888
.L7:
lea rdx, [rax+1] # D.1888,
cmp rax, rcx # D.1888, D.1848
jl .L24 #,
which iterates many times (rcx > 1<<32), and maybe the whole loop is executed
more than once
Tested revisions:
r168296 - fail
