Summary:
In NEON, the immediate forms of VBIC and VORR are each represented as
a single MC instruction, which takes its immediate operand already
encoded in a NEON-friendly format: 8 data bits, plus some control bits
indicating how to expand them into a full vector.
In MVE, we represented immediate VBIC and VORR as four separate MC
instructions each, for an 8-bit immediate shifted left by 0, 8, 16 or
24 bits. For each one, the value of the immediate operand is in the
'natural' form, i.e. the numerical value that would actually be BICed
or ORRed into each vector lane (and also the same value shown in
assembly). For example, MVE_VBICIZ16v4i32 takes an operand such as
0xab0000, which NEON would represent as 0xab | (control bits << 8).
The MVE approach is superficially nice (it makes assembly input and
output easy, and it's also nice if you're manually constructing
immediate VBICs). But it turns out that it's better for isel if we
make the NEON and MVE instructions work the same, because the
ARMISD::VBICIMM and VORRIMM node types already encode their immediate
into the NEON format, so it's easier if we can just use it.
Also, this commit reduces the total amount of code rather than
increasing it, which is surely an indication that it really is simpler
to do it this way!
Reviewers: dmgreen, ostannard, miyuki, MarkMurrayARM
Reviewed By: dmgreen
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D73205
The hasSideEffect parameter is usually automatically inferred from
instruction patterns. For some of our MVE instructions, we do not have
patterns though, such as for the pre/post inc loads and stores. This
instead specifies the flag manually on the base MVE_VLDRSTR_base
tablegen class, making sure we get this correct.
This can help with scheduling multiple loads more optimally. Here I've
added a unittest as a more direct form of testing.
Differential Revision: https://reviews.llvm.org/D73117
We have a whitelist of instructions that we allow when tail
predicating, since these are trivial ones that we've deemed need no
special handling. Now change ARMLowOverheadLoops to allow the
non-trivial instructions if they're contained within a valid VPT
block. Since a valid block is one that is predicated upon the VCTP so
we know that these non-trivial instructions will still behave as
expected once the implicit predication is used instead.
This also fixes a previous test failure.
Differential Revision: https://reviews.llvm.org/D72509
We've been marking VPT incompatible instructions as invalid for tail
predication too, though this may not strictly be true. VPT are
incompatible and, unless its the first predicate def in a loop,
they shouldn't be compatible for tail predication either.
Differential Revision: https://reviews.llvm.org/D71410
Summary:
The immediate forms of the MVE VQSHL instruction have MC names like
`MVE_VSLIimms8` and `MVE_VSLIimmu32`. Those names are confusing,
because VSLI is a completely different shift instruction with no
semantic relation to VQSHL. But it just happens to be defined
immediately before VQSHL in `ARMInstrMVE.td`, so this looks like a
copy-paste error. Renamed the ids to match the instruction name.
Reviewers: ostannard, dmgreen, MarkMurrayARM, miyuki
Reviewed By: miyuki
Subscribers: kristof.beyls, hiraditya, llvm-commits
Tags: #llvm
Differential Revision: https://reviews.llvm.org/D71114
This patch modifies ARMLowOverheadLoops to convert a predicated
vector low-overhead loop into a tail-predicatd one. This is currently
a very basic conversion, with the following restrictions:
- Operates only on single block loops.
- The loop can only contain a single vctp instruction.
- No other instructions can write to the vpr.
- We only allow a subset of the mve instructions in the loop.
TODO: Pass the number of elements, not the number of iterations to
dlstp/wlstp.
Differential Revision: https://reviews.llvm.org/D69945
Reverse the logic for valid tail predication instructions and create
a whitelist instead. Added other instruction groups that aren't
obviously safe:
- instructions that 'narrow' their result.
- lane moves.
- byte swapping instructions.
- interleaving loads and stores.
- cross-beat carries.
- top/bottom instructions.
- complex operations.
Hopefully we should be able to add more of these instructions to the
whitelist, once we have a more concrete idea of the transform.
Differential Revision: https://reviews.llvm.org/D67904
llvm-svn: 374887
Set this bit for the MVE reduction instructions to prevent a loop from
becoming tail predicated in their presence.
Differential Revision: https://reviews.llvm.org/D67444
llvm-svn: 372076
