The attached fix to the Ada front-end introduces a regression in the ACATS 
testsuite for cb4009a.  The backtrace is:

#0  operation_could_trap_helper_p(tree_code, bool, bool, bool, bool, 
tree_node*, bool*) () at /home/eric/gnat/gnat-head/src/gcc/tree-eh.c:2439
#1  0x00000000012946d7 in stmt_could_throw_1_p (stmt=<optimized out>)
    at /home/eric/gnat/gnat-head/src/gcc/tree-eh.c:2759
#2  stmt_could_throw_p(gimple*) [clone .part.186] ()
    at /home/eric/gnat/gnat-head/src/gcc/tree-eh.c:2809
#3  0x0000000001295f28 in stmt_could_throw_p (stmt=0x7ffff6c5d420)
    at /home/eric/gnat/gnat-head/src/gcc/tree-eh.c:2924
#4  maybe_clean_or_replace_eh_stmt (old_stmt=old_stmt@entry=0x7ffff6c565d8, 
    new_stmt=new_stmt@entry=0x7ffff6c5d420)
    at /home/eric/gnat/gnat-head/src/gcc/tree-eh.c:2908
#5  0x0000000000fd8a0b in gsi_replace(gimple_stmt_iterator*, gimple*, bool) ()
    at /home/eric/gnat/gnat-head/src/gcc/gimple-iterator.c:447
#6  0x0000000000fd14af in 
gimple_assign_set_rhs_with_ops(gimple_stmt_iterator*, tree_code, tree_node*, 
tree_node*, tree_node*) ()
    at /home/eric/gnat/gnat-head/src/gcc/gimple.c:1616
#7  0x0000000000fe7af7 in replace_stmt_with_simplification (inplace=false, 
    seq=0x7fffffffd818, ops=0x7fffffffd820, rcode=..., gsi=0x7fffffffd8e0)
    at /home/eric/gnat/gnat-head/src/gcc/gimple-fold.c:4151
#8  fold_stmt_1(gimple_stmt_iterator*, bool, tree_node* (*)(tree_node*)) ()
    at /home/eric/gnat/gnat-head/src/gcc/gimple-fold.c:4462
#9  0x0000000000fe961a in fold_stmt (gsi=gsi@entry=0x7fffffffd8e0, 
    valueize=valueize@entry=0x1331170 <fwprop_ssa_val(tree)>)
    at /home/eric/gnat/gnat-head/src/gcc/gimple-fold.c:4689

The folding is turning a TRUNC_DIV_EXPR into a COND_EXPR and the code does:

  /* If the new CODE needs more operands, allocate a new statement.  */
  if (gimple_num_ops (stmt) < new_rhs_ops + 1)
    {
      tree lhs = gimple_assign_lhs (stmt);
      gimple *new_stmt = gimple_alloc (gimple_code (stmt), new_rhs_ops + 1);
      memcpy (new_stmt, stmt, gimple_size (gimple_code (stmt)));
      gimple_init_singleton (new_stmt);
      gsi_replace (gsi, new_stmt, true);
      stmt = new_stmt;

      /* The LHS needs to be reset as this also changes the SSA name
	 on the LHS.  */
      gimple_assign_set_lhs (stmt, lhs);
    }

i.e it asks gsi_replace to update EH info, which doesn't work since the new 
statement is dummy at this point.  Fixed by passing false instead of true.

Bootstrapped/regtested on x86_64-suse-linux, applied on mainline as obvious.


2017-07-25  Eric Botcazou  <ebotcazou@adacore.com>

	* gimple.c (gimple_assign_set_rhs_with_ops): Do not ask gsi_replace
	to update EH info here.


2017-07-25  Javier Miranda  <miranda@adacore.com>

ada/
	* checks.adb (Apply_Divide_Checks): Ensure that operands are not
	evaluated twice. 


2017-07-25  Eric Botcazou  <ebotcazou@adacore.com>

testsuite/
	* gnat.dg/opt66.adb: New test.


-- 
Eric Botcazou