Re: [patch, fortran] Fix PR 82567
On 10/17/2017 03:36 PM, Thomas Koenig wrote: > Hello world, > > this patch fixes a regression with long compile times, > which came about due to our handling of array constructors > at compile time. This, togeteher with a simplification in > front end optimization, led to long compile times and large > code. > > Regression-tested. OK for trunk and the other affected branches? > Well I know 42 is the answer to the ultimate question of the universe so this must be OK. I just don't know what the question is. OK and thanks, Jerry +#define CONSTR_LEN_MAX 42 +
Re: [patch, fortran] Fix PR 82567
On Tue, Oct 17, 2017 at 06:14:16PM -0700, Jerry DeLisle wrote: > On 10/17/2017 03:36 PM, Thomas Koenig wrote: > > Hello world, > > > > this patch fixes a regression with long compile times, > > which came about due to our handling of array constructors > > at compile time. This, togeteher with a simplification in > > front end optimization, led to long compile times and large > > code. > > > > Regression-tested. OK for trunk and the other affected branches? > > > > Well I know 42 is the answer to the ultimate question of the universe so this > must be OK. I just don't know what the question is. > > OK and thanks, > > Jerry > > +#define CONSTR_LEN_MAX 42 Actually, I was wondering about the choice myself. With most common hardware having fairly robust L1 and L2 cache sizes, a double precision array constructor with 42 elements only occupies 336 bytes. Seems small. -- Steve 20170425 https://www.youtube.com/watch?v=VWUpyCsUKR4 20161221 https://www.youtube.com/watch?v=IbCHE-hONow
Re: [patch, fortran] Fix PR 82567
Le 18/10/2017 à 04:05, Steve Kargl a écrit : On Tue, Oct 17, 2017 at 06:14:16PM -0700, Jerry DeLisle wrote: On 10/17/2017 03:36 PM, Thomas Koenig wrote: Hello world, this patch fixes a regression with long compile times, which came about due to our handling of array constructors at compile time. This, togeteher with a simplification in front end optimization, led to long compile times and large code. Regression-tested. OK for trunk and the other affected branches? Well I know 42 is the answer to the ultimate question of the universe so this must be OK. I just don't know what the question is. OK and thanks, Jerry +#define CONSTR_LEN_MAX 42 Actually, I was wondering about the choice myself. With most common hardware having fairly robust L1 and L2 cache sizes, a double precision array constructor with 42 elements only occupies 336 bytes. Seems small. There is a -fmax-array-constructor=n option. Can’t we use it for the limit?
Re: [patch, fortran] Fix PR 82567
Hi Jerry and Steve, Well I know 42 is the answer to the ultimate question of the universe so this must be OK. I just don't know what the question is. OK and thanks, Jerry +#define CONSTR_LEN_MAX 42 Actually, I was wondering about the choice myself. With most common hardware having fairly robust L1 and L2 cache sizes, a double precision array constructor with 42 elements only occupies 336 bytes. Seems small. Well, the answer is that I didn't know how to chose a reasonable constant. I now actually ran some benchmarks using rdtsc, and these seem to indicate that the optimum value for CONST_LEN_MAX is actually quite short, 3 or 4, otherwise I just got a slowdown or a break even. So, I committed (r253872) with a length of 4 as a limit. If anybody comes up with a better number, we can always change this. So, thanks for the review and the comments. Regards Thomas If somebody wants to check, here is the test case: main.f90: module tick interface function rdtsc() integer(kind=8) :: rdtsc end function rdtsc end interface end module tick program main use tick use tst implicit none integer(8) :: t1, t2 t1 = rdtsc() call sub1(2.0) t2 = rdtsc() ! print *,"sub1 : ", t2-t1 t1 = rdtsc() do i=1,1 call sub1(2.0) end do t2 = rdtsc() print *,"sub1 : ", t2-t1 t1 = rdtsc() do i=1,1 call sub2(2.0) end do t2 = rdtsc() print *,"sub2 : ", t2-t1 end program main tst.f90: module tst integer, parameter :: n=4 real, dimension(n) :: x real, dimension(n), parameter :: s = [(i,i=1,n)] contains subroutine sub1(a) real, intent(in) :: a x(1) = a * 1.0 x(2) = a * 2.0 x(3) = a * 3.0 x(4) = a * 3.0 end subroutine sub1 subroutine sub2(a) x(:) = a * s(:) end subroutine sub2 end module tst rdtsc.s: .file "rdtsc.s" .text .globl rdtsc_ .type rdtsc_, @function rdtsc_: .LFB0: .cfi_startproc rdtsc shl $32, %rdx or %rdx, %rax ret .cfi_endproc .LFE0: .size rdtsc_, .-rdtsc_ .section.note.GNU-stack,"",@progbits
