[Patch,fortran] PR28914 Code inside loop hangs

[Jerry DeLisle <jvdelisle at verizon dot net>]

The following patch was contributed by Paul Thomas.  I am assisting getting this 
out for 4.2 release.

The attached patch fixes this problem by creating a temporary copy of the loop 
variable used by the constructor so that it does not corrupt that variable if 
used in a surrounding DO LOOP.  The loop variable is restored after the 
constructor is done.

Regression tested on i686-linux-pc-gnu.

OK to commit to 4.2?

Regards,

Jerry

2006-09-09  Paul Thomas <pault@gcc.gnu.org>

	PR fortran/28914
	* trans-array.c (gfc_trans_array_constructor_value): Create a temporary
	loop variable to hold the current loop variable in case it is modified
	by the array constructor.

Index: trans-array.c
===================================================================
*** trans-array.c	(revision 116710)
--- trans-array.c	(working copy)
*************** gfc_trans_array_constructor_value (stmtb
*** 1252,1257 ****
--- 1252,1258 ----
  	  tree exit_label;
  	  tree loopbody;
  	  tree tmp2;
+ 	  tree tmp_loopvar;
  
  	  loopbody = gfc_finish_block (&body);
  
*************** gfc_trans_array_constructor_value (stmtb
*** 1260,1265 ****
--- 1261,1272 ----
  	  gfc_add_block_to_block (pblock, &se.pre);
  	  loopvar = se.expr;
  
+ 	  /* In case this is a variable in the function scope,
+ 	     make a temporary, store the current value in that
+ 	     and return it, once the loop is done.  */
+ 	  tmp_loopvar = gfc_create_var (TREE_TYPE (loopvar), "loopvar");
+ 	  gfc_add_modify_expr (pblock, tmp_loopvar, loopvar);
+ 
  	  /* Initialize the loop.  */
  	  gfc_init_se (&se, NULL);
  	  gfc_conv_expr_val (&se, c->iterator->start);
*************** gfc_trans_array_constructor_value (stmtb
*** 1327,1332 ****
--- 1334,1342 ----
  	  /* Add the exit label.  */
  	  tmp = build1_v (LABEL_EXPR, exit_label);
  	  gfc_add_expr_to_block (pblock, tmp);
+ 
+ 	  /* Restore the original value of the loop counter.  */
+ 	  gfc_add_modify_expr (pblock, loopvar, tmp_loopvar);
  	}
      }
    mpz_clear (size);

! { dg-do run }
! Tests the fix for pr28914, in which array constructors using the loop
! variable within a do loop for the implied do loop of the constructor
! would result in a corrupted do loop counter.
!
! Based on the testscase by Ed Korkven <kornkven@arsc.edu>
!
program pr28914
  implicit none
  integer n, i
  parameter (n = 66000) ! Problem manifests for n > 65535
  double precision a(n), summation

  summation = 0.0
  do i = 1, 1
    a = (/ (i, i = 1, n) /) ! This is legal and was broken
    a = sqrt(a)
    summation = SUM(a)
  enddo
  summation = abs(summation - 11303932.9138271_8)
  
  if (summation.gt.0.00001)   call abort()
end program pr28914