[Bug target/18631] [4.0 Regression] missing error messages passing vectors with -mno-altivec -mabi=altivec

["janis187 at us dot ibm dot com" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From janis187 at us dot ibm dot com  2004-11-24 16:53 -------
Oops, in the submission I said "There used to be error messages for passing
vectors by value or returning vectors from functions if AltiVec support was on
but the non-AltiVec ABI was used."  That should be: There used to be error
messages ... if AltiVec support was not on and the AltiVec ABI was used.

The AltiVec ABI says that vectors that map to hardware vectors are passed in
vector registers.  That variant of the ABI is the default but can be turned
off with -mabi=no-altivec, which is useful for binary compatibility with
modules that will be used on multiple types of PowerPC-64 hardware.  The ABI
doesn't cover generic vectors that don't map to hardware vectors, but GCC
passes them by reference for either variant of the ABI.  It probably doesn't
specifically cover the case of generic vectors that map to hardware vectors
when AltiVec support isn't enabled, but that seems surprising enough that it
ought to continue to be an error.

I personally think it ought to be an error to pass any synthetic vector by
value unless it is specifically covered by the ABI, but that's another mess
that no one wants to touch.

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18631