RS6000 emitting sign extention for unsigned type

[Jakub Jelinek]

On Fri, Jan 18, 2019 at 11:03:28PM +1030, Alan Modra wrote:
> On Tue, Jan 15, 2019 at 04:48:27PM +0530, kamlesh kumar wrote:
> > Hi all,
> > 
> > Analysed it further and find out that
> > function ' rs6000_promote_function_mode ' (rs6000.c) needs modifcation.
> > """
> > static machine_mode
> > rs6000_promote_function_mode (const_tree type ATTRIBUTE_UNUSED,
> >                               machine_mode mode,
> >                               int *punsignedp ATTRIBUTE_UNUSED,
> >                               const_tree, int)
> > {
> >   PROMOTE_MODE (mode, *punsignedp, type);
> >   return mode;
> > }
> > """
> > Here, This function is promoting the mode but
> > it is not even touching 'punsignedp' and it is always initialized to zero
> > by default.
> > So in all cases 'punsignedp' remain zero even if it is for unsigned type.
> > which cause the sign extension to happen  even for unsigned type.
> > 
> > is there any way to set 'punsignedp' appropriately here.
> 
> No.  The call to promote_function_mode in emit_library_call_value_1
> does not pass type info (because it isn't available for libcalls).

Yeah, all the callers of emit_library_call* would need to be changed to pass
triplets rtx, machine_mode, int/bool /*unsignedp*/, instead of just
rtx_mode_t pair or add a new set of emit_library_call* APIs that would take
those triplets.

	Jakub