[Bug c/68062] [4.9/5/6 Regression] ICE when comparing vectors

[rguenther at suse dot de]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68062

--- Comment #9 from rguenther at suse dot de <rguenther at suse dot de> ---
On Thu, 12 Nov 2015, uweigand at gcc dot gnu.org wrote:

> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68062
> 
> --- Comment #8 from Ulrich Weigand <uweigand at gcc dot gnu.org> ---
> (In reply to Richard Biener from comment #7)
> > I think there was some inconsistencies in C vs. C++ FEs in this area (but as
> > usual I don't remember exactly but I remember Uli complaining about it again
> > at the Caulrdon).
> > 
> > I believe it was sort-of automatic integer promotion rules should apply if
> > they don't change vector sizes (thus, the sign promotion parts should apply).
> > 
> > That's not "ignoring" signs but doing the appropriate (view-)conversions.
> 
> Actually, the C vs. C++ FE inconsistency was about binary operators (+, -,
> ...), not comparisons.
> 
> For both binary and relational operators, the various applicable standards
> (AltiVec + extensions, System z vector extensions, OpenCL) all agree that if
> the two operands differ in signedness, the operation is not valid and should
> result in an error.  However, GCC has never done this, but has always accepted
> these combinations (both C and C++).  (At some point, we might want to change
> this, but then we have to care that we don't break "vector bool" handling for
> those platforms that support it.)
> 
> The difference between C and C++ comes in when determining what to use as the
> *result type* of a binary operator whose operands differ in signedness.  This
> does not apply to comparisons since those have a result type different from the
> input types in any case.

Thanks for the clarification.