[Bug other/19815] Documentation change - GCC Internals MODES_TIEABLE_P

[abnikant dot singh at atmel dot com]

------- Comment #1 from abnikant dot singh at atmel dot com  2009-08-19 11:57 -------
"If HARD_REGNO_MODE_OK (r, mode1) and HARD_REGNO_MODE_OK (r, mode2) are always
the same for any r, then MODES_TIEABLE_P (mode1, mode2) should be nonzero. If
they differ for any r, you should define this macro to return zero unless some
other mechanism ensures the accessibility of the value in a narrower mode."

                        In case of avr:
if (mode1 != mode2) then HARD_REGNO_MODE_OK (r, mode1) != HARD_REGNO_MODE_OK
(r, mode2) and hence MODES_TIEABLE_P (mode1, mode2) should be 0. [ But this is
true only if we do not have other mechanism to access the value in narrower
mode ]


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19815