These compute the average of two given values, rounding up and down,
respectively, if the result isn't exact. When possible, these are
mapped to target-specific intrinsics (PADD[BW] on IA and VH[R]ADD[US]
on NEON.)
A subsequent commit will add pattern-matching to generate calls to
these intrinsincs when the corresponding patterns are detected in the
IR.)
Like SSE4-8 and SSE4-16, these use 8-bit and 16-bit values for mask
elements, respectively, and thus should generate the best code when used
for computation with datatypes of those sizes.
This change adds a new 'sse4-8' target, where programCount is 16 and
the mask element size is 8-bits. (i.e. the most appropriate sizing of
the mask for SIMD computation with 8-bit datatypes.)
There were a number of places throughout the system that assumed that the
execution mask would only have either 32-bit or 1-bit elements. This
commit makes it possible to have a target with an 8- or 16-bit mask.
We now have two ways of approaching gather/scatters with a common base
pointer and with offset vectors. For targets with native gather/scatter,
we just turn those into base + {1/2/4/8}*offsets. For targets without,
we turn those into base + {1/2/4/8}*varying_offsets + const_offsets,
where const_offsets is a compile-time constant.
Infrastructure for issue #325.
No functional change; just preparation for having a path that doesn't
factor the offsets into constant and varying parts, which will be better
for AVX2 and KNC.
1. For some time now, we provide the version without the 'svn'
2. We should be testing "not LLVM 3.0" in these cases, since they
apply to LLVM 3.2 and beyond as well...
Now that we never ever run with the mask all off, we no longer need
that logic in a built-in function so that we can check the mask. In
the one place where it was used (turning gathers to the same location
into a load and broadcast), we now just emit the code for that
directly.
Previously, we'd bitcast e.g. a vector of floats to a vector of i32s and then
use the i32 variant of masked_load/masked_store/gather/scatter. Now, we have
separate float/double variants of each of those.
Change function suffix to "_i32", etc, from "_32"
Improve load_and_broadcast macro in util.m4 to grab vector width from
WIDTH variable rather than taking it as a parameter.
When we're able to turn a general gather/scatter into the "base + offsets"
form, we now try to extract out any constant components of the offsets and
then pass them as a separate parameter to the gather/scatter function
implementation.
We then in turn carefully emit code for the addressing calculation so that
these constant offsets match LLVM's patterns to detect this case, such that
we get the constant offsets directly encoded in the instruction's addressing
calculation in many cases, saving arithmetic instructions to do these
calculations.
Improves performance of stencil by ~15%. Other workloads unchanged.
