[tree-ssa] FIX_.*_EXPR

[Paul Brook]

Unlike C, Fortran allows the user to specify which rounding mode should be 
used when converyting floating point values to integers.

in tree.def there are declarations for FIX_CEIL_EXPR, FIX_FLOOR_EXPR and 
FIX_ROUND_EXPR. However these don't seem to be implemented by the current 
RTL expander. It aborts in expr.c when these are used.

Is there any chance of getting these implemented? Unfortunately I have 
approximately zero knowledge of RTL, so wouldn't know where to start.

Failing that I think it would be a good idea to handle these during 
gimplification. If it's decided that they aren't going to be part of 
GIMPLE, I'd be willing to create a patch which converted them to 
BUILTIN_FLOOR_EXPR or similar.

It does seem a bit strange having expression nodes and builtin functions 
that do the smae thing.

Paul Brook