[Bug middle-end/57073] __builtin_powif (-1.0, k) should be optimized to "1.0 - 2.0 * (K%2)"

[tkoenig at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57073



--- Comment #4 from Thomas Koenig <tkoenig at gcc dot gnu.org> 2013-04-28 
22:03:35 UTC ---

Created attachment 29968

  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29968

patch that fails



The patch in the attachment fails with the test

case



program main

  integer :: i

  real(8) :: a

  a = -1.0_8

  read (*,*) i

  print *,(-1.0_8)**i,a**i

end program main



gfortran -O foo.f90

foo.f90: In function 'MAIN__':

foo.f90:6:0: internal compiler error: in gimplify_modify_expr, at

gimplify.c:4941

   print *,(-1.0_8)**i,a**i

 ^

0x7fbc17 gimplify_modify_expr

        ../../trunk/gcc/gimplify.c:4941

0x7f0211 gimplify_expr(tree_node**, gimple_statement_d**, gimple_statement_d**,

bool (*)(tree_node*), int)

        ../../trunk/gcc/gimplify.c:7156



I wonder why.