This relands a6ca88e908 which was originally
reverted due to overflow bugs in e3fa2b1eab.
This patch teaches the compiler to identify a wider variety of
`BUILD_VECTOR`s which form integer arithmetic sequences, and to lower
them to `vid.v` with modifications for non-unit steps and non-zero
addends.
The sequences handled by this optimization must either be monotonically
increasing or decreasing. Consecutive elements holding the same value
indicate a fractional step which, while simple mathematically,
becomes more complex to handle both in the realm of lossy integer
division and in the presence of `undef`s.
For example, a common "interleaving" shuffle index will be lowered by
LLVM to both `<0,u,1,u,2,...>` and `<u,0,u,1,u,...>` `BUILD_VECTOR`
nodes. Either of these would ideally be lowered to `vid.v` shifted right
by 1. Detection of this sequence in presence of general `undef` values
is more complicated, however: `<0,u,u,1,>` could match either
`<0,0,0,1,>` or `<0,0,1,1,>` depending on later values in the sequence.
Both are possible, so backtracking or multiple passes is inevitable.
Sticking to monotonic sequences keeps the logic simpler as it can be
done in one pass. Fractional steps will likely be a separate
optimization in a future patch.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D104921
This patch teaches the compiler to identify a wider variety of
`BUILD_VECTOR`s which form integer arithmetic sequences, and to lower
them to `vid.v` with modifications for non-unit steps and non-zero
addends.
The sequences handled by this optimization must either be monotonically
increasing or decreasing. Consecutive elements holding the same value
indicate a fractional step which, while simple mathematically,
becomes more complex to handle both in the realm of lossy integer
division and in the presence of `undef`s.
For example, a common "interleaving" shuffle index will be lowered by
LLVM to both `<0,u,1,u,2,...>` and `<u,0,u,1,u,...>` `BUILD_VECTOR`
nodes. Either of these would ideally be lowered to `vid.v` shifted right
by 1. Detection of this sequence in presence of general `undef` values
is more complicated, however: `<0,u,u,1,>` could match either
`<0,0,0,1,>` or `<0,0,1,1,>` depending on later values in the sequence.
Both are possible, so backtracking or multiple passes is inevitable.
Sticking to monotonic sequences keeps the logic simpler as it can be
done in one pass. Fractional steps will likely be a separate
optimization in a future patch.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D104921
In most of cases, it has a single space after comma in assembly operands.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D103790
We aren't going to connect the result to anything so we might
as well avoid allocating a register.
Reviewed By: frasercrmck, HsiangKai
Differential Revision: https://reviews.llvm.org/D102031
My thought process is that if v2i64 is an LMUL=1 type then v2i32
should be an LMUL=1/2 type. We limit the fractional LMUL so that
SEW=64 clips to LMUL=1, SEW=32 clips to LMUL=1/2, etc. This
ensures there's always a fractional LMUL available to truncate a type.
This does reduce the number of vsetvlis in some cases.
Some tests increase vsetvlis because the best container type for a
mask type is dependent on the LMUL+SEW that the mask was produced
from, but you can't tell that from the type. I think this is
something we need to solve this in the machine IR when optimizing
vsetvlis.
Reviewed By: frasercrmck
Differential Revision: https://reviews.llvm.org/D101215
This adds almost everything required for supporting the new stepvector
intrinsic on RVV. It is lowered to the existing VID_VL SDNode.
The only exception is a limitation that RV32 cannot yet lower the
intrinsic on i64 vectors. This is because the step operand is
(currently) required to be at least as large as the vector element type.
I will look into patching that out and loosening the requirement to only
an integer pointer type.
Reviewed By: craig.topper
Differential Revision: https://reviews.llvm.org/D99594
Fraser Cormack