Hi folks,
This patch cuts the compilation time for some programs with large array
constructors in half. It does this by traversing the constructor and
only calling the more complicated expand_constructor for expression
types that are EXPR_ARRAY.
Since gfc_constant_ac can be called recursively, this simplification
indeed has significant benefit.
I do not see a real need for another test case since all it would
accomplish is lengthen the time it takes to run the test suite. One
interesting side effect of this was an ICE in
gfc_conv_array_constructor_expr, at fortran/trans-expr.c:3832. This
occurs with the following test case where the limit of 65535 is exceeded.
integer, parameter :: n=65536
integer, parameter :: i(n)=(/(mod(k,2),k=1,n)/)
integer, parameter :: m(n)=i(n:1:-1)
print *, i(1), m(1), i(n), m(n)
end
This takes several minutes before hitting the error:
integer, parameter :: i(n)=(/(mod(k,2),k=1,n)/)
1
Error: The number of elements in the array constructor at (1) requires
an increase of the allowed 65535 upper limit. See
-fmax-array-constructor option
The ICE occurs after the error message.
I tried several ways to avoid the ICE with no avail. I opted to change
the error to a gfc_fatal_error. If one thinks about it, this really is a
fatal error.
The test case which shows the improvement is:
program sel
implicit none
integer,parameter :: n=1000
integer :: i,j
real,dimension(n*n) :: vect
vect(:) = (/ ((( (i+j+3)),i=1,n),j=1,n) /)
end
$ time gfc44 pr20923.f90
real 0m18.616s
user 0m17.173s
sys 0m0.063s
$ time gfc pr20923.f90
real 0m9.467s
user 0m8.764s
sys 0m0.044s
Regression tested on x86-64=linux-gnu. OK for trunk? Is this sufficient
to close the PR or shall I leave it open?
Regards,
Jerry
2009-12-04 Jerry DeLisle <jvdelisle@gcc.gnu.org>
PR fortran/20923
* trans-array.c (gfc_conv_array_initializer): Change gfc_error_now to
gfc_fatal_error.
* array.c (count_elements): Whitespace. (extract_element): Whitespace.
(is_constant_element): Changed name from constant_element.
(gfc_constant_element): Only use expand_construuctor for expression
types of EXPR_ARRAY. If expression type is EXPR_CONSTANT, no need to
call gfc_is_constant_expr.