[llvm-commits] PATCH: remove VICmp and VFCmp.

[David Greene]

On Thursday 09 July 2009 13:20, Chris Lattner wrote:
> > Storing an <8 x i1> to memory with the same layout as [8 x i1] -- as
> > 8 bytes -- has the nice property of being friendly to various LLVM
> > assumptions. Unfortunately, it's also highly artificial; existing
> > vector hardware I'm familiar with doesn't work that way, and it
> > seems unlikely that anyone ever would want it to. However, it might
> > be ok for LLVM to define <8 x i1> stores this way for consistency
> > and then tell everyone to avoid using them.

So what's the alternative?  Bitcast to i8 and then store?

> If a specific piece of hardware has support for "vectors of bools" in
> some way, they will probably have intrinsics to load/store them in
> their own specific format.

But what would be the result type of these memory operations?  Intrinsics
for load/store of vector masks is ok.  In a previous message I thought you
had suggested that all masked vector operations be intrinsics.  That's a
non-starter in the long run (it's fine for an initial working implementation).

If <N x i1> is defined to be bitpacked except when storing to memory, that
should be ok.  Then we can use intrinsics to load/store vector masks and
have the resulting type of the load by <N x i1> which is natural.

Either that or we define a new bitvector type.

                                      -Dave