These are essentially add/sub 1 with a clamping value.
AMDGPU has instructions for these. CUDA/HIP expose these as
atomicInc/atomicDec. Currently we use target intrinsics for these,
but those do no carry the ordering and syncscope. Add these to
atomicrmw so we can carry these and benefit from the regular
legalization processes.
LLVM currently uses LDAR/STLR and variants for acquire/release
as well as seq_cst operations. This is fine as long as all code uses
this convention.
Normally LDAR/STLR act as one way barriers but when used in
combination they provide a sequentially consistent model. i.e.
when an LDAR appears after an STLR in program order the STLR
acts as a two way fence and the store will be observed before
the load.
The problem is that normal loads (unlike ldar), when they appear
after the STLR can be observed before STLR (if my understanding
is correct). Possibly providing weaker than expected guarantees if
they are used for ordered atomic operations.
Unfortunately in Microsoft Visual Studio STL seq_cst ld/st are
implemented using normal load/stores and explicit fences:
dmb ish + str + dmb ish
ldr + dmb ish
This patch uses fences for MSVC target whenever we write to the
memory in a sequentially consistent way so that we don't rely on
the assumptions that just using LDAR/STLR will give us sequentially
consistent ordering.
Differential Revision: https://reviews.llvm.org/D141748
Change-Id: I48f3500ff8ec89677c9f089ce58181bd139bc68a
Use deduction guides instead of helper functions.
The only non-automatic changes have been:
1. ArrayRef(some_uint8_pointer, 0) needs to be changed into ArrayRef(some_uint8_pointer, (size_t)0) to avoid an ambiguous call with ArrayRef((uint8_t*), (uint8_t*))
2. CVSymbol sym(makeArrayRef(symStorage)); needed to be rewritten as CVSymbol sym{ArrayRef(symStorage)}; otherwise the compiler is confused and thinks we have a (bad) function prototype. There was a few similar situation across the codebase.
3. ADL doesn't seem to work the same for deduction-guides and functions, so at some point the llvm namespace must be explicitly stated.
4. The "reference mode" of makeArrayRef(ArrayRef<T> &) that acts as no-op is not supported (a constructor cannot achieve that).
Per reviewers' comment, some useless makeArrayRef have been removed in the process.
This is a follow-up to https://reviews.llvm.org/D140896 that introduced
the deduction guides.
Differential Revision: https://reviews.llvm.org/D140955
The 32-bit floating-point atomic add instructions on AMDGPUs does not support a
"flat" or "generic" address space. So, if the address space cannot be determined
statically, the AMDGPU backend will fall back to a CAS loop (which does support
"flat" addressing). Instead, this patch emits runtime address-space checks to
allow native FP atomic add instructions for global and LDS memory (and non-atomic
FP add instructions for private/scratch memory).
In order to do that, this patch introduces a new interface function
`emitExpandAtomicRMW`. It is expected to be called when a common atomic expand
doesn't work for a specific target, such as the case we discussed here.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D129690
This removes the ptrtoint from the load's pointer operand, although we
can't entirely eliminate these to get the LSB shift. In a future
patch, this will avoid ptrtoint in the case where the atomic is
overaligned to the word size.
When expanding IR atomics to target-specific atomics, copy all
!pcsections Metadata to expanded atomics automatically.
Reviewed By: vitalybuka
Differential Revision: https://reviews.llvm.org/D130885
IIUC, the conversion part is not part of atomic operations and fences should be put around converted atomic operations.
This also fixes atomic load of floating point values which requires fence on PowerPC.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D127609
This patch adds the support for `fmax` and `fmin` operations in `atomicrmw`
instruction. For now (at least in this patch), the instruction will be expanded
to CAS loop. There are already a couple of targets supporting the feature. I'll
create another patch(es) to enable them accordingly.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D127041
This adds support for pointer types for `atomic xchg` and let us write
instructions such as `atomicrmw xchg i64** %0, i64* %1 seq_cst`. This
is similar to the patch for allowing atomicrmw xchg on floating point
types: https://reviews.llvm.org/D52416.
Differential Revision: https://reviews.llvm.org/D124728
Currently for atomic load, store, and rmw instructions, as long as the
operand is floating-point value, they are casted to integer. Nowadays many
targets can actually support part of atomic operations with floating-point
operands. For example, NVPTX supports atomic load and store of floating-point
values. This patch adds a series interface functions `shouldCastAtomicXXXInIR`,
and the default implementations are same as what we currently do. Later for
targets can have their specialization.
Reviewed By: jdoerfert
Differential Revision: https://reviews.llvm.org/D125652
Currently LowerAtomics exists as a separate pass which blindly
replaces all atomics. Add a new lowering strategy option to eliminate
the atomics which the target can control on a per-instruction level.
Use the same enum as the other atomic instructions for consistency, in
preparation for addition of another strategy.
Introduce a new "Expand" option, since the store expansion does not
use cmpxchg. Alternatively, the existing CmpXChg strategy could be
renamed to Expand.
Fixes llvm-clang-x86_64-expensive-checks-debian failure with 2f497ec3.
expandAtomicStore always modifies the function, so make sure we set
MadeChange unconditionally. Not sure how nobody else has stumbled over
this before.
When generating a all-one mask value whose bitwidth is larger than 64, signed extension should be used rather then zero extension.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D120865
This reverts commit 7f230feeeac8a67b335f52bd2e900a05c6098f20.
Breaks CodeGenCUDA/link-device-bitcode.cu in check-clang,
and many LLVM tests, see comments on https://reviews.llvm.org/D121169
Produce remarks when atomic instructions are expanded into hardware instructions
in SIISelLowering.cpp. Currently, these remarks are only emitted for atomic fadd
instructions.
Differential Revision: https://reviews.llvm.org/D108150
This patch uses AtomicExpandPass to implement quadword lock free atomic operations. It adopts the method introduced in https://reviews.llvm.org/D47882, which expand atomic operations post RA to avoid spilling that might prevent LL/SC progress.
Reviewed By: jsji
Differential Revision: https://reviews.llvm.org/D103614
If we're not emitting separate fences for the success/failure cases, we
need to pass the merged ordering to the target so it can emit the
correct instructions.
For the PowerPC testcase, we end up with extra fences, but that seems
like an improvement over missing fences. If someone wants to improve
that, the PowerPC backed could be taught to emit the fences after isel,
instead of depending on fences emitted by AtomicExpand.
Fixes https://bugs.llvm.org/show_bug.cgi?id=33332 .
Differential Revision: https://reviews.llvm.org/D103342
Follow the same strategy used for atomic loads/stores by converting the operands to equally-sized integer types.
This change prevents the atomic expansion pass from generating illegal LL/SC pairs when targeting AArch64: `expand-atomicrmw-xchg-fp.ll` would previously instantiate intrinsics such as `llvm.aarch64.ldaxr.p0f32` that cannot be lowered.
Reviewed By: efriedma
Differential Revision: https://reviews.llvm.org/D103232
And then push those change throughout LLVM.
Keep the old signature in Clang's CGBuilder for now -- that will be
updated in a follow-on patch (D97224).
The MLIR LLVM-IR dialect is not updated to support the new alignment
attribute, but preserves its existing behavior.
Differential Revision: https://reviews.llvm.org/D97223
I recently modified this pass to better support CHERI-RISC-V and while
doing so I noticed that this pass was calling M->getOrInsertFunction()
with the result of TLI->getLibcallName(RTLibType). However, AMDGPU fills
the libcalls array with nullptr, so this creates an anonymous function
instead. This patch changes expandAtomicOpToLibcall to return false in
case the libcall does not exist and changes the assert() in the callees to
a report_fatal_error() instead.
Reviewed By: arsenm
Differential Revision: https://reviews.llvm.org/D88800
In cases where the alignment of the datatype is smaller than
expected by the instruction, the address is aligned. The aligned
address is used for the load, but wasn't used for the store
conditional, which resulted in a run-time alignment exception.
