Some processors benefit more from store clustering than load clustering,
and vice-versa, depending on factors that are exclusive to each one
(e.g. macrofusions implemented).
Likewise, certain optimizations benefits more from misched clustering
than postRA clustering. Macrofusions are again an example: in a
processor with store pair macrofusions, like the veyron-v1, it is
observed that misched clustering increases the amount of macrofusions
more than postRA clustering. This of course isn't necessarily true for
other processors, but it shows that processors can benefit from a more
fine grained control of clustering mutations, and each one is able to do
it differently.
Add 4 new subtarget features that deprecates the existing
riscv-misched-load-store-clustering and
riscv-postmisched-load-store-clustering
options:
- disable-misched-load-clustering and disable-misched-store-clustering:
disable load/store clustering during misched;
- disable-postmisched-load-clustering and
disable-postmisched-store-clustering:
disable load/store clustering during PostRA.
Note that the new subtarget features disables specific stages of the
default
clustering settings. The default per se (load and store clustering for
both
misched and PostRA) is left untouched.
Disable all clustering but misched-store-clustering for the veyron-v1
processor
using the new features.
When vectorizing a loop with a fixed-order recurrence we use a splice,
which gets lowered to a vslidedown and vslideup pair.
However with the way we lower it today we end up with extra vl toggles
in the loop, especially with EVL tail folding, e.g:
.LBB0_5: # %vector.body
# =>This Inner Loop Header: Depth=1
sub a5, a2, a3
sh2add a6, a3, a1
zext.w a7, a4
vsetvli a4, a5, e8, mf2, ta, ma
vle32.v v10, (a6)
addi a7, a7, -1
vsetivli zero, 1, e32, m2, ta, ma
vslidedown.vx v8, v8, a7
sh2add a6, a3, a0
vsetvli zero, a5, e32, m2, ta, ma
vslideup.vi v8, v10, 1
vadd.vv v8, v10, v8
add a3, a3, a4
vse32.v v8, (a6)
vmv2r.v v8, v10
bne a3, a2, .LBB0_5
Because the vslideup overwrites all but UpOffset elements from the
vslidedown, we currently set the vslidedown's AVL to said offset.
But in the vslideup we use either VLMAX or the EVL which causes a
toggle.
This increases the AVL of the vslidedown so it matches vslideup, even if
the extra elements are overridden, to avoid the toggle.
A new tuning feature +vl-dependent-latency has been added which keeps
the old behaviour for microarchitectures that dynamically dispatch uops
based on vl, e.g. sifive-x280.
+vl-dependent-latency can be reused for the recently proposed Ovlt
optimization directive if/when it's ratified:
https://lists.riscv.org/g/tech-privileged/message/2487
If we wanted to aggressively optimise for vl at the expense of
introducing more toggles we could probably look at doing this in
RISCVVLOptimizer.
XAndesVPackFPH can actually be used independently without requiring
Zvfhmin. Therefore, we remove the implicitly required Zvfhmin extension
from XAndesVPackFPH and imply that the f extension is sufficient.
As far as I know binutils does not have a similar option and I don't
know of a reason we shouldn't accept the RVC hint instructions.
The wording in the spec in the past suggested that maybe these
weren't valid instruction names, but that's been modified recently.
As of 20b5728b7b1ccc4509a316efb270d46cc9526d69, C always enables Zca, so
the check `C || Zca` is equivalent to just checking for `Zca`.
This replaces any uses of `HasStdExtCOrZca` with a new `HasStdExtZca`
(with the same assembler description, to avoid changes in error
messages), and simplifies everywhere where C++ needed to check for
either C or Zca.
The Subtarget function is just deprecated for the moment.
- The double trap extension requires `mtval2' register, so add Zicsr as
required extension
Signed-off-by: Jerry Zhang Jian <jerry.zhangjian@sifive.com>
This adds assembler/disassembler support for XSfmmbase 0.6 and related
SiFive matrix multiplication extensions based on the spec here
https://www.sifive.com/document-file/xsfmm-matrix-extensions-specification
Functionality-wise, this is the same as the Zvma extension proposal that
SiFive shared with the Attached Matrix Extension Task Group. The
extension names and instruction mnemonics have been changed to use
vendor prefixes.
Note this is a non-conforming extension as the opcodes used here are in
the standard opcode space in OP-V or OP-VE.
---------
Co-authored-by: Brandon Wu <brandon.wu@sifive.com>
This updates all the extensions to their version in the v0.11.0 spec.
All changes from this version are already implemented or are not
relevant to LLVM.
This change also alphabetises the lists of Xqci extensions, to make
future checks easier, and removes irrelevant info from the usage docs.
This Change adds support for two SiFive vendor attributes in clang:
- "SiFive-CLIC-preemptible"
- "SiFive-CLIC-stack-swap"
These can be given together, and can be combined with "machine", but
cannot be combined with any other interrupt attribute values.
These are handled primarily in RISCVFrameLowering:
- "SiFive-CLIC-stack-swap" entails swapping `sp` with `sf.mscratchcsw`
at function entry and exit, which holds the trap stack pointer.
- "SiFive-CLIC-preemptible" entails saving `mcause` and `mepc` before
re-enabling interrupts using `mstatus`. To save these, `s0` and `s1`
are first spilled to the stack, and then the values are read into
these registers. If these registers are used in the function, their
values will be spilled a second time onto the stack with the generic
callee-saved-register handling. At the end of the function interrupts
are disabled again before `mepc` and `mcause` are restored.
This Change also adds support for the following two experimental
extensions, which only contain CSRs:
- XSfsclic - for SiFive's CLIC Supervisor-Mode CSRs
- XSfmclic - for SiFive's CLIC Machine-Mode CSRs
The latter is needed for interrupt support.
The CFI information for this implementation is not correct, but I'd
prefer to correct this in a follow-up. While it's unlikely anyone wants
to unwind through a handler, the CFI information is also used by
debuggers so it would be good to get it right.
Co-authored-by: Ana Pazos <apazos@quicinc.com>
This extension adds two external input output instructions for
non-memory-mapped device.
The current spec can be found at:
https://github.com/quic/riscv-unified-db/releases/tag/Xqci-0.7.0
This patch adds assembler only support.
Co-authored-by: Sudharsan Veeravalli <quic_svs@quicinc.com>
This implements [the `.option exact` and `.option noexact`
proposal](https://github.com/riscv-non-isa/riscv-asm-manual/pull/122)
for RISC-V.
`.option exact` turns off:
- Compression
- Branch Relaxation
- Linker Relaxation
`.option noexact` turns these back on, and is also the default, matching
the current behaviour.
With a minor fix for the build failures.
Original message:
This extension adds nine instructions, eight for non-memory-mapped devices synchronization and delay instruction.
The current spec can be found at:
https://github.com/quic/riscv-unified-db/releases/tag/Xqci-0.7.0
This patch adds assembler only support.
Co-authored-by: Sudharsan Veeravalli quic_svs@quicinc.com
This extension adds nine instructions, eight for non-memory-mapped
devices synchronization and delay instruction.
The current spec can be found at:
https://github.com/quic/riscv-unified-db/releases/tag/Xqci-0.7.0
This patch adds assembler only support.
Co-authored-by: Sudharsan Veeravalli <quic_svs@quicinc.com>
Currently, we use `csrr` with `vlenb` to obtain the `VLEN`, but this is
not the only option. We can also use `vsetvli` with `e8`/`m1` to get
`VLENMAX`, which is equal to the VLEN. This method is preferable on some
microarchitectures and makes it easier to obtain values like `VLEN * 2`,
`VLEN * 4`, or `VLEN * 8`, reducing the number of instructions needed to
calculate VLEN multiples.
However, this approach is *NOT* always interchangeable, as it changes
the state of `VTYPE` and `VL`, which can alter the behavior of vector
instructions, potentially causing incorrect code generation if applied
after a vsetvli insertion. Therefore, we limit its use to the
prologue/epilogue for now, as there are no vector operations within the
prologue/epilogue sequence.
With further analysis, we may extend this approach beyond the
prologue/epilogue in the future, but starting here should be a good
first step.
This feature is gurded by the `+prefer-vsetvli-over-read-vlenb` feature,
which is disabled by default for now.
