Re: [tree-ssa] bootstrap problem on powerpc-apple-darwin6.6

[law at redhat dot com]

In message <622F711B-D416-11D7-B633-000393A6D2F2@physics.uc.edu>, Andrew Pinski
 writes:
 >Here is more reduced sources:
 >union tree_node;
 >typedef union tree_node *tree;
 >typedef enum fallback_t {
 >   fb_none = 0,
 >   fb_rvalue=1,
 >   fb_lvalue=2,
 >   fb_either=1|2
 >} fallback_t;
 >
 >int
 >gimplify_expr (tree *expr_p, fallback_t fallback)
 >{
 >if ((fallback & fb_rvalue) && *expr_p)
 >     {
 >         f_temp_2();
 >     }
 >   else
 >     {
 >         abort();
 >     }
 >   return 1;
 >}
 >
 >
 >The problem is gimplify_expr (which is weird as this is the function 
 >which is causing this ICE)
 >These lines on 491-494:
 >	  /* Strip away as many useless type conversions as possible
 >	     at the toplevel.  */
 >	  while (tree_ssa_useless_type_conversion (*expr_p))
 >	    *expr_p = TREE_OPERAND (*expr_p, 0);
 >is removing the conversion to boolean_type:
 > From tree_ssa_useless_type_conversion:
 >       /* If both the inner and outer types are integral types, then
 >          we can enter the equivalence if they have the same mode
 >          and signedness.  */
 >       else if (INTEGRAL_TYPE_P (inner_type) && INTEGRAL_TYPE_P 
 >(outer_type)
 >	       && TYPE_MODE (inner_type) == TYPE_MODE (outer_type)
 >	       && TREE_UNSIGNED (inner_type) == TREE_UNSIGNED (outer_type))
 >	return true;
 >which is true in this case which cause it to remove the nop_expr which 
 >converts to boolean_type.
 >
 >Jeff you added tree_ssa_useless_type_conversion can you say what is 
 >going on and why is this happening?
It's pretty self explanatory -- it's trying to remove type conversions which
are unnecessary.  I would ask, why do you think the conversion is necessary
in the first place?  It's possible y'all have summarized this already and
I simply missed it -- in which case just point me to the appropriate point
in the archives.

jeff