[Bug fortran/42189] gfc_is_constant_expr has unacceptable side effects

["jvdelisle at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>]

------- Comment #3 from jvdelisle at gcc dot gnu dot org  2009-12-05 04:17 -------
Studying this with a little instrumentation, I see that gfc_expand_constructor
is called only once with some of the test cases for pr20923.  This is good. 
Also, in the test case for pr41807, the work function constant_element does
nothing but check that the element is constant.  In the patch for pr20923 I
will submit shortly, I have renamed it to is_constant_element which is clearer.

Moving on, the is_constant_element work function and the other constructor work
functions are called by expand_constructor.  expand_constructor calls
gfc_simplify_expr.  It is possible that gfc_simplify_expr is called more than
once on a given constructor expr as the various work functions are exercised. I
have not confirmed this.  I wonder if it would make sense to add a flag to
gfc_expr to mark it as having been simplified already and do an early exit from
it for efficiency.

I will do some testing to see if it is indeed being called more than once and
report back.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42189