Commit Graph

10 Commits

Author SHA1 Message Date
Jim Lin 242ddd5089 [RISCV][NFC] Add a single space after comma for VType
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
2021-06-09 11:18:22 +08:00
Fraser Cormack 8790e85255 [RISCV] Reserve an emergency spill slot for any RVV spills
This patch addresses an issue in which fixed-length (VLS) vector RVV
code could fail to reserve an emergency spill slot for their frame index
elimination. This is because we were previously only reserving a spill
slot when there were `scalable-vector` frame indices being used.
However, fixed-length codegen uses regular-type frame indices if it
needs to spill.

This patch does the fairly brute-force method of checking ahead of time
whether the function contains any RVV spill instructions, in which case
it reserves one slot. Note that the second RVV slot is still only
reserved for `scalable-vector` frame indices.

This unfortunately causes quite a bit of churn in existing tests, where
we chop and change stack offsets for spill slots.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D103269
2021-06-03 10:44:34 +01:00
Craig Topper 527cd01314 [RISCV] Teach vsetvli insertion to use vsetvl x0, x0 form when we can tell that VLMAX and AVL haven't changed.
This can help avoid needing a virtual register for the vsetvl output
when the AVL is X0. For other register AVLs it can shorter the live
range of the AVL register if it isn't needed later.

There's probably no advantage when AVL is a 5 bit immediate that
can use vsetivli. But do it anyway for consistency.

Reviewed By: rogfer01

Differential Revision: https://reviews.llvm.org/D103215
2021-05-27 10:11:38 -07:00
Fraser Cormack 8c73a31c11 [RISCV] Allow passing fixed-length vectors via the stack
The vector calling convention dictates that when the vector argument
registers are exhaused, GPRs are used to pass the address via the stack.
When the GPRs themselves are exhausted, at best we would previously
crash with an assertion, and at worst we'd generate incorrect code.

This patch addresses this issue by passing fixed-length vectors via the
stack with their full fixed-length size and aligned to their element
type size. Since the calling convention lowering can't yet handle
scalable vector types, this patch adds a fatal error to make it clear
that we are lacking in this regard.

Reviewed By: HsiangKai

Differential Revision: https://reviews.llvm.org/D102422
2021-05-27 14:14:07 +01:00
Craig Topper fdf10e6197 [RISCV] Use X0 as destination of inserted vsetvli when possible.
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
2021-05-26 13:08:51 -07:00
Fraser Cormack 797e580db9 [RISCV][NFC] Simplify test run lines
Several tests had -verify-machineinstrs twice, and several tests were
explicitly specifying the default FileCheck prefix of CHECK.
2021-05-13 12:41:00 +01:00
Craig Topper ce6e4f27dd [RISCV] Use fractional LMULs for fixed length types smaller than riscv-v-vector-bits-min.
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
2021-05-11 09:42:48 -07:00
Fraser Cormack 43ad058a01 [RISCV] Fix stack slot for argument types (Bug 49500)
This is an complementary/alternative fix for D99068. It takes a slightly
different approach by explicitly summing up all of the required split
part type sizes and ensuring we allocate enough space for them. It also
takes the maximum alignment of each part.

Compared with D99068 there are fewer changes to the stack objects in
existing tests. However, @luismarques has shown in that patch that there
are opportunities to reduce our stack usage in the future.

Reviewed By: luismarques

Differential Revision: https://reviews.llvm.org/D99087
2021-04-29 09:10:48 +01:00
Craig Topper ce09dd54e6 [RISCV] Select 5 bit immediate for VSETIVLI during isel rather than peepholing in the custom inserter.
This adds a special operand type that is allowed to be either
an immediate or register. By giving it a unique operand type the
machine verifier will ignore it.

This perturbs a lot of tests but mostly it is just slightly different
instruction orders. Something bad did happen to some min/max reduction
tests. We're spilling vector registers when we weren't before.

Reviewed By: khchen

Differential Revision: https://reviews.llvm.org/D101246
2021-04-27 14:38:16 -07:00
Fraser Cormack 0c5b789c73 [RISCV] Support fixed-length vectors in the calling convention
This patch adds fixed-length vector support to the calling convention
when RVV is used to lower fixed-length vectors. The scheme follows the
regular vector calling convention for the argument/return registers, but
uses scalable vector container types as the LocVTs, and converts to/from
the fixed-length vector value types as required.

Fixed-length vector types may be split when the combination of minimum
VLEN and the maximum allowable LMUL is not large enough to fully contain
the vector. In this case the behaviour differs between fixed-length
vectors passed as parameters and as return values:
1. For return values, vectors must be passed entirely via registers or
via the stack.
2. For parameters, unlike scalar values, split vectors continue to be
passed by value, and are split across multiple registers until there are
no remaining registers. Thus vector parameters may be found partly in
registers and partly on the stack.

As with scalable vectors, the first fixed-length mask vector is passed
via v0. Split mask fixed-length vectors are passed first via v0 and then
via the next available vector register: v8,v9,etc.

The handling of vector return values uses all available argument
registers v8-v23 which does not adhere to the calling convention we're
supposedly implementing, but since this issue affects both fixed-length
and scalable-vector values, it was left as-is.

Reviewed By: craig.topper

Differential Revision: https://reviews.llvm.org/D97954
2021-03-15 10:43:51 +00:00