212 Commits

Author SHA1 Message Date
Johannes de Fine Licht
758be971dc [mlir:LLVM] Rudimentary inlining support for LLVM load store.
Conservatively only allow inlining for loads and stores that don't carry
any attributes that require handling while inlining. This can later be
relaxed when proper handling is introduced.

Reviewed By: Dinistro, gysit

Differential Revision: https://reviews.llvm.org/D141115
2023-01-09 10:28:21 +01:00
Slava Zakharin
2f66c89130 [mlir] Support TBAA metadata in LLVMIR dialect.
This change introduces new LLVMIR dialect operations to represent
TBAA root, type descriptor and access tag metadata nodes.

For the purpose of importing TBAA metadata from LLVM IR it only
supports the current version of TBAA format described in
https://llvm.org/docs/LangRef.html#tbaa-metadata (i.e. size-aware
representation introduced in D41501 is not supported).

TBAA attribute support is only added for LLVM::LoadOp and LLVM::StoreOp.
Support for intrinsics operations (e.g. LLVM::MemcpyOp) may be added later.

The TBAA attribute is represented as an array of access tags, though,
LLVM IR supports only single access tag per memory accessing instruction.
I implemented it as an array anticipating similar support in LLVM IR
to combine TBAA graphs with different roots for Flang - one of the options
described in https://docs.google.com/document/d/16kKZVmI585wth01VSaJAqZMZpoX68rcdBmgfj0kNAt0/edit#heading=h.jzzheaz9vqac

It should be easy to restrict MLIR operation to a single access tag,
if we end up using a different approach for Flang.

Differential Revision: https://reviews.llvm.org/D140768
2023-01-06 11:16:31 -08:00
Mehdi Amini
551ec87883 Use --pass-pipeline syntax for mlir/test/Dialect/LLVMIR/canonicalize.mlir (NFC)
This is just a cleanup to make the scheduling of the pass pipeline
explicit.
2023-01-05 10:22:49 +00:00
Matthias Springer
e7790fbed3 [mlir] Add test-convergence option to Canonicalizer tests
This new option is set to `false` by default. It should  be set only in Canonicalizer tests to detect faulty canonicalization patterns. I.e., patterns that prevent the canonicalizer from converging. The canonicalizer should always convergence on such small unit tests that we have in `canonicalize.mlir`.

Two faulty canonicalization patterns were detected and fixed with this change.

Differential Revision: https://reviews.llvm.org/D140873
2023-01-04 12:02:21 +01:00
Ingo Müller
3a43e68ed1 Allow inline of all pure ops from the LLVM dialect.
This allows to inline regions containing pure LLVM ops into their call
sites. (Note that this is not related to inlining of llvm.func but to
any the inlining of any Callable.) For now, we only allow the inlining
of Pure ops to be conservative but other ops may be considered inlinable
in the future.

Testing for purity of ops requires the C++ equivalent of the Pure trait
from SideEffectInterfaces.td, which this patch also provide. Its
implementation calls the C++ equivalents of the two traits that the Pure
trait is based on and, thus, has to be kept with the tablegen trait.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D139187
2022-12-14 15:18:37 +00:00
Tobias Gysi
7b420a1ada [mlir][llvm] Add inbounds attriubte to the gep op.
The revision adds an inbounds attribute to the LLVM dialect
GEP operation. It extends the builders and the import and export
to support the optional inbounds attribute.

As all builders set inbounds to false by default, existing lowerings
from higher-level dialects to LLVM dialect are not affected by the
change. Canonicalization/folding remains untouched since it currently
does not implement any simplifications in case of undefined behavior
(the handling of undefined behavior is deferred to LLVM).

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D139821
2022-12-14 10:46:07 +01:00
Mehdi Amini
88c5b9640a Add LLVMDialect as dependent for "llvm-legalize-for-export" pass
Fixes #59462
2022-12-13 08:49:13 +00:00
Jeff Niu
34535801d6 [mlir] UnsignedWhenEquivalent ignore dead code
The pass was not checking for uninitialized states due to dead code.
This patch also makes LLVMFuncOp correctly return a null body when it is
external.

Fixes #58807

Depends on D139388

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D139389
2022-12-05 20:38:44 -08:00
Tobias Gysi
36fa80b046 [mlir][llvm] Make additional int debug attribute parameters optional.
The revision makes additional integer debug info parameters such as
line or column numbers optional (e.g. the line and column numbers 0 are
elided when printing, which is in line with the LLVM implementation).

Depends on D138405

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D138437
2022-11-29 14:02:58 +02:00
Tobias Gysi
be4b49407e [mlir][llvm] Import debug intrinsics from LLVMIR.
Currently, the import of LLVMIR fails if the program contains debug
intrinsics. The revision adds support to import debug intrinsics that
have no debug expression attached and drops all debug intrinsics with a
non-empty debug expression. It also moves the existing debug intrinsics
into the "intr" namespace by deriving from LLVM_IntrOp.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D138405
2022-11-29 12:31:54 +02:00
Hanhan Wang
0a1569a400 [mlir][NFC] Remove trailing whitespaces from *.td and *.mlir files.
This is generated by running

```
sed --in-place 's/[[:space:]]\+$//' mlir/**/*.td
sed --in-place 's/[[:space:]]\+$//' mlir/**/*.mlir
```

Reviewed By: rriddle, dcaballe

Differential Revision: https://reviews.llvm.org/D138866
2022-11-28 15:26:30 -08:00
Slava Zakharin
29016d2830 [mlir][llvmir] Translate function result attributes to LLVM IR.
Translate align, noalias, noundef, signext and zeroext result
attributes from llvm.func to LLVM IR.

This is needed for https://github.com/llvm/llvm-project/issues/58579

Differential Revision: https://reviews.llvm.org/D137049
2022-11-18 12:03:42 -08:00
Tobias Gysi
63502901ca [mlir][llvm] Make some debug info attribute parameters optional.
The revision makes specific debug information attribute parameters
optional since some of them can be omitted in LLVMIR. The additional
flexibility enables a later revision that will support importing
debug information from LLVMIR. A special case is the types parameter
of the SubroutineTypeAttr. For void functions, its first entry is
null in LLVMIR. This revision splits the type parameter in an optional
resultType parameter and an argumentTypes array to support this corner
case.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D138206
2022-11-18 09:35:44 +01:00
Slava Zakharin
473d001152 [mlir][llvmir] Convert attributes for functions without bodies.
So far the function argument attributes were only translated
for functions with bodies. This change makes sure that this
happens for functions without bodies (declarations) as well.

This is needed for https://github.com/llvm/llvm-project/issues/58579

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D137047
2022-11-03 08:52:19 -07:00
rkayaith
13bd410962 [mlir][Pass] Include anchor op in -pass-pipeline
In D134622 the printed form of a pass manager is changed to include the
name of the op that the pass manager is anchored on. This updates the
`-pass-pipeline` argument format to include the anchor op as well, so
that the printed form of a pipeline can be directly passed to
`-pass-pipeline`. In most cases this requires updating
`-pass-pipeline='pipeline'` to
`-pass-pipeline='builtin.module(pipeline)'`.

This also fixes an outdated assert that prevented running a
`PassManager` anchored on `'any'`.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D134900
2022-11-03 11:36:12 -04:00
electriclilies
0efff7cdcb [mlir] Add call_intrinsic op to LLVMIIR
The call_intrinsic op allows us to call LLVM intrinsics from the LLVMDialect without implementing a new op every time.

Reviewed By: lattner, rriddle

Differential Revision: https://reviews.llvm.org/D137187
2022-11-02 15:56:46 -07:00
Slava Zakharin
35c9085121 [mlir][llvmir] Support FastmathFlags for LLVM intrinsic operations.
This is required for D126305 code to propagate fastmath attributes
for Arith operations that are converted to LLVM IR intrinsics
operations.

LLVM IR intrinsic operations are using custom assembly format now
to avoid printing {fastmathFlags = #llvm.fastmath<none>}, which
is too verbose.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D136225
2022-11-02 12:41:47 -07:00
River Riddle
3bef1e0f4c [mlir:LLVM] Add attribute/op definitions for debug info
This adds a subset of the necessary metadata for defining
debug info in the LLVM dialect. It doesn't import everything,
but just enough to start actually generating LLVM debug info
the expected way. Export/Import to LLVMIR will be added in a
followup.

Differential Revision: https://reviews.llvm.org/D136542
2022-10-23 23:59:55 -07:00
River Riddle
29bb0b5e1d [mlir] Generate parser/printers for enums
This greatly simplifies composing enums in attribute/type printers,
which currently reimplement these functions as needed.

Differential Revision: https://reviews.llvm.org/D136407
2022-10-21 15:32:36 -07:00
Jeff Niu
a9bde16ba5 [mlir][llvm] Move LLVMPointerType to TypeDef
Depends on D136485

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D136498
2022-10-21 15:13:08 -07:00
Jeff Niu
8c8775e938 [mlir][llvm] Move LLVMArrayType to a TypeDef
This moves the `LLVMArrayType` to a `TypeDef`. The main side-effect of
this change is that the syntax `array<4xi32>` is no longer allowed. It
was previously parsed and then printed as `array<4 x i32>`. Now the
syntax must be the latter.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D136473
2022-10-21 12:57:16 -07:00
Jeremy Furtek
dd38f89980 [mlir][LLVMIR] Update LLVMIR fastmath to use EnumAttr tblgen classes
This diff updates the `fastmath` attribute in the LLVMIR dialect to use `tblgen`
classes that were developed after the initial LLVMIR `fastmath` implementation.
Using the `EnumAttr` `tblgen` classes brings the LLVMIR `fastmath` attribute in
line with other dialects, and eliminates some of the custom printing and parsing
code in the LLVMIR dialect.

Subsequent commits will further reduce the custom processing code for the LLVMIR
`fastmath` attribute by unifying printing/parsing functionality between the
LLVMIR and `arith` `fastmath` attributes. (The actual attributes will remain
separate, but the printing and parsing will be made generic, and will be usable
by other dialects/attributes.)

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D135289
2022-10-17 15:03:47 -07:00
Guray Ozen
040805dc47 [mlir] Add bar.warp.sync to NVVM
It adds the missing `bar.warp.sync` to the nvvm dialect. It is a barrier to synchronize for threads in a warp.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D135253
2022-10-06 12:27:53 +02:00
Min-Yih Hsu
b4869f2fa7 [mlir][LLVMIR] Fix incorrect result type from llvm.fcmp
If any of the operands for FCmpOp is a vector, returns a vector<Nxi1>,
rather than an i1 type result.

Differential Revision: https://reviews.llvm.org/D134449
2022-09-27 09:56:54 -07:00
Jeff Niu
e63b574ff6 [mlir][LLVMIR] Add lifetime start and end marker instrinsics
This patch adds the `llvm.intr.lifetime.start` and `llvm.intr.lifetime.end`
intrinsics which are used to indicate to LLVM the lifetimes of allocated
memory.

These ops have the requirement that the first argument (the size) be an
"immediate argument". I added an OpTrait to check this, but it is
possible that an approach like GEPArg would work too.

Reviewed By: rriddle, dcaballe

Differential Revision: https://reviews.llvm.org/D133867
2022-09-14 13:15:14 -07:00
Alexander Batashev
79c2094881 [mlir][LLVMIR] Parse some type attributes for LLVM function parameters
With the transition to opaque pointers, type information has been
transferred to function parameter attributes. This patch adds correct
parsing for some of those arguments and fixes some tests, that
previously used UnitAttr for those.

Differential Revision: https://reviews.llvm.org/D132366
2022-08-25 11:06:51 +03:00
Slava Zakharin
13cb085ca1 [mlir] Support llvm.readnone attribute for all FunctionOpInterface ops.
The attribute is translated into LLVM's function attribute 'readnone'.
There is no explicit verification regarding conflicting 'readnone'
and function attributes from 'passthrough', though, LLVM would assert
if they are incompatible during LLVM IR creation.

Differential Revision: https://reviews.llvm.org/D131457
2022-08-24 10:12:37 -07:00
Jacques Pienaar
7d273fde11 [mlir] Populate default attributes on op creation
Default attributes were only handled by ODS accessors generated with the
intention that these behave as if set attributes. This addresses the
long standing TODO to address this inconsistency. Moving the
initialization to construction vs every access. Removing need for
duplicated default attribute population in python bindings.

Switch some of the OpenMP ones to optional attribute with default as the
currently set default values are not legal. May need to dig more there.

Switched LinAlg generated ones to optional attribute with default as its
quite widely used and unclear where it falls on two different
interpretations.

Differential Revision: https://reviews.llvm.org/D130916
2022-08-22 16:49:46 -07:00
Jeff Niu
a48ff68888 [mlir][LLVMIR] "Modernize" LLVM insert/extract element operations
This patch "modernizes" the implementation of these operations by
switching them to assembly formats and type inference traits.

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D131971
2022-08-18 14:43:06 -04:00
Jeff Niu
b2ccfb4d95 [mlir][LLVMIR] Change ShuffleVectorOp to use assembly format
This patch moves `LLVM::ShuffleVectorOp` to assembly format and in the
process drops the extra type that can be inferred (both operand types
are required to be the same) and switches to a dense integer array.

The syntax change:

```
// Before
%0 = llvm.shufflevector %0, %1 [0 : i32, 0 : i32, 0 : i32, 0 : i32] : vector<4xf32>, vector<4xf32>
// After
%0 = llvm.shufflevector %0, %1 [0, 0, 0, 0] : vector<4xf32>
```

Reviewed By: dcaballe

Differential Revision: https://reviews.llvm.org/D132038
2022-08-18 12:46:04 -04:00
Jeff Niu
2092d1438c [mlir] Change the syntax of dense arrays
Follow-up to D123774, where the syntax of dense arrays was discussed. It
was included that the syntax should be changed to `array<i32: 1, 2>`.
This patch changes the syntax but importantly preserves the `[1, 2]`
syntax when embedding these attributes in assembly formats through ODS.

Reviewed By: mehdi_amini, jpienaar

Differential Revision: https://reviews.llvm.org/D131738
2022-08-11 20:56:42 -04:00
Jeff Niu
5c5af910fe [mlir][LLVMIR] "Modernize" Insert/ExtractValueOp
This patch "modernizes" the LLVM `insertvalue` and `extractvalue`
operations to use DenseI64ArrayAttr, since they only require an array of
indices and previously there was confusion about whether to use i32 or
i64 arrays, and to use assembly format.

Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D131537
2022-08-10 12:51:11 -04:00
Eugene Zhulenev
51bc82d147 [mlir] Implement SymbolUserOpInterface in LLVM::CallOp
Avoid expensive calls to `SymbolTable::lookupNearestSymbolFrom` in verifier

Reviewed By: Mogball

Differential Revision: https://reviews.llvm.org/D131285
2022-08-05 13:50:31 -07:00
Eugene Zhulenev
292e8ed49a [mlir] Use SymbolUserOpInterface in LLVM::AddressOfOp verifier
Reviewed By: Mogball

Differential Revision: https://reviews.llvm.org/D131271
2022-08-05 10:51:30 -07:00
Jeff Niu
e179532284 [mlir] Remove types from attributes
This patch removes the `type` field from `Attribute` along with the
`Attribute::getType` accessor.

Going forward, this means that attributes in MLIR will no longer have
types as a first-class concept. This patch lays the groundwork to
incrementally remove or refactor code that relies on generic attributes
being typed. The immediate impact will be on attributes that rely on
`Attribute` containing a type, such as `IntegerAttr`,
`DenseElementsAttr`, and `ml_program::ExternAttr`, which will now need
to define a type parameter on their storage classes. This will save
memory as all other attribute kinds will no longer contain a type.

Moreover, it will not be possible to generically query the type of an
attribute directly. This patch provides an attribute interface
`TypedAttr` that implements only one method, `getType`, which can be
used to generically query the types of attributes that implement the
interface. This interface can be used to retain the concept of a "typed
attribute". The ODS-generated accessor for a `type` parameter
automatically implements this method.

Next steps will be to refactor the assembly formats of certain operations
that rely on `parseAttribute(type)` and `printAttributeWithoutType` to
remove special handling of type elision until `type` can be removed from
the dialect parsing hook entirely; and incrementally remove uses of
`TypedAttr`.

Reviewed By: lattner, rriddle, jpienaar

Differential Revision: https://reviews.llvm.org/D130092
2022-07-31 20:01:31 -04:00
Markus Böck
37da2a141c [mlir][LLVM] Rework the API of GEPOp
The implementation and API of GEP Op has gotten a bit convoluted over the time. Issues with it are:
* Misleading naming: `indices` actually only contains the dynamic indices, not all of them. To get the amount of indices you need to query the size of `structIndices`
* Very difficult to iterate over all indices properly: One had to iterate over `structIndices`, check whether it contains the magic constant `kDynamicIndex`, if it does, access the next value in `index` etc.
* Inconvenient to build: One either has create lots of constant ops for every index or have an odd split of passing both a `ValueRange` as well as a `ArrayRef<int32_t>` filled with `kDynamicIndex` at the correct places.
* Implementation doing verification in the build method
and more.

This patch attempts to address all these issues via convenience classes and reworking the way GEP Op works:
* Adds `GEPArg` class which is a sum type of a `int32_t` and `Value` and is used to have a single convenient easy to use `ArrayRef<GEPArg>` in the builders instead of the previous `ValueRange` + `ArrayRef<int32_t>` builders.
* Adds `GEPIndicesAdapter` which is a class used for easy random access and iteration over the indices of a GEP. It is generic and flexible enough to also instead return eg. a corresponding `Attribute` for an operand inside of `fold`.
*  Rename `structIndices` to `rawConstantIndices` and `indices` to `dynamicIndices`: `rawConstantIndices` signifies one shouldn't access it directly as it is encoded, and `dynamicIndices` is more accurate and also frees up the `indices` name.
* Add `getIndices` returning a `GEPIndicesAdapter` to easily iterate over the GEP Ops indices.
* Move the verification/asserts out of the build method and into the `verify` method emitting op error messages.
* Add convenient builder methods making use of `GEPArg`.
* Add canonicalizer turning dynamic indices with constant values into constant indices to have a canonical representation.

The only breaking change is for any users building GEPOps that have so far used the old `ValueRange` + `ArrayRef<int32_t>` builder as well as those using the generic syntax.

Another follow up patch then goes through upstream and makes use of the new `ArrayRef<GEPArg>` builder to remove a lot of code building constants for GEP indices.

Differential Revision: https://reviews.llvm.org/D130730
2022-07-29 18:22:54 +02:00
Markus Böck
7a67e41be2 [mlir][LLVM] Fix incorrect GEP fold with struct constants
The fold in it's current state only checks whether the amount of dynamic indices is 1. This does however not check for the presence of any struct indices, leading to an incorrect fold.

This patch fixes that issue by checking that struct indices are 1, which in addition to the pre-existing check that dynamic indices are 1, guarantees that the single index is a dynamic one.

Differential Revision: https://reviews.llvm.org/D129374
2022-07-27 14:42:35 +02:00
Min-Yih Hsu
a2158374ba [mlir][LLVMIR] Apply CallOp/CallableInterface on suitable operations
- Applying CallOpInterface on CallOp and InvokeOp.
  - Applying CallableInterface on LLVMFuncOp.

We're testing the changes using CallGraph, which uses both interfaces.

Differential Revision: https://reviews.llvm.org/D129026
2022-07-05 09:27:00 -07:00
Min-Yih Hsu
856056d1b0 [mlir][LLVMIR] Add support for va_start/copy/end intrinsics
This patch adds three new LLVM intrinsic operations: llvm.intr.vastart/copy/end.
And its translation from LLVM IR.

This effectively removes a restriction, imposed by 0126dcf1f0a1, where
non-external functions in LLVM dialect cannot be variadic. At that time
it was not clear how LLVM intrinsics are going to be modeled, which
indirectly affects va_start/copy/end, the core intrinsics used in
variadic functions. But since we have LLVM intrinsics as normal
MLIR operations, it's not a problem anymore.

Differential Revision: https://reviews.llvm.org/D127540
2022-06-27 09:46:40 -07:00
Javier Setoain
f39c2a1142 [mlir][llvm] Add vector insert/extract intrinsics
These intrinsics will be needed to convert between fixed-length vectors
and scalable vectors.

This operation will be needed for VLS (vector-length specific)
vectorization, when interfacing with vector functions or intrinsics that
take scalable vectors as operands in a context where the length of our
vectors is known or assumed at compile time, but we still want to
generate scalable vector instructions.

Differential Revision: https://reviews.llvm.org/D127100
2022-06-27 14:12:18 +01:00
Krzysztof Drewniak
8e61fdc727 [mlir][ROCDL] Define MLIR wrappers around new MFMA intrinsics
In order to support newer hardware, define wrappers around MFMA
intrinsics that have not previously been exposed in the ROCDL dialect.

A `amdgpu.mfma` wrapper around these instructions is in development
and will provide a more user-friendly interface to them.

Reviewed By: ThomasRaoux

Differential Revision: https://reviews.llvm.org/D128079
2022-06-20 15:03:45 +00:00
Alex Zinenko
610139d2d9 [mlir] replace 'emit_c_wrappers' func->llvm conversion option with a pass
The 'emit_c_wrappers' option in the FuncToLLVM conversion requests C interface
wrappers to be emitted for every builtin function in the module. While this has
been useful to bootstrap the interface, it is problematic in the longer term as
it may unintentionally affect the functions that should retain their existing
interface, e.g., libm functions obtained by lowering math operations (see
D126964 for an example). Since D77314, we have a finer-grain control over
interface generation via an attribute that avoids the problem entirely. Remove
the 'emit_c_wrappers' option. Introduce the '-llvm-request-c-wrappers' pass
that can be run in any pipeline that needs blanket emission of functions to
annotate all builtin functions with the attribute before performing the usual
lowering that accounts for the attribute.

Reviewed By: chelini

Differential Revision: https://reviews.llvm.org/D127952
2022-06-17 11:10:31 +02:00
Min-Yih Hsu
cd8978e19e [mlir][LLVMIR] Ask ICmpOp to return vector<Nxi1> when needed
If any of the operands for ICmpOp is a vector, returns a vector<Nxi1>
, rather than an i1 type result.

Differential Revision: https://reviews.llvm.org/D127536
2022-06-15 14:33:48 -07:00
Min-Yih Hsu
719e24d39f [mlir][LLVMIR] Use isScalableVectorType in ShuffleVectorOp::parse
Instead of casting the incoming operand into VectorType to check if it's
scalable or not.
This is the place I missed to fix in f088b99eac74.

Differential Revision: https://reviews.llvm.org/D127535
2022-06-15 14:33:48 -07:00
Mogball
ba79bb4973 [mlir][nvvm] Change MMAShapeAttr to AttrDef
MMAShapeAttr was a StructAttr

Reviewed By: rriddle

Differential Revision: https://reviews.llvm.org/D127348
2022-06-09 22:14:45 +00:00
lorenzo chelini
9b3712e0bf [MLIR][LLVMIR] Add round intrinsic
Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D126879
2022-06-07 10:27:55 +02:00
Christian Sigg
400fef081a Recommit: "[MLIR][NVVM] Replace fdiv on fp16 with promoted (fp32) multiplication with reciprocal plus one (conditional) Newton iteration."
This change rolls bcfc0a9051014437b55ab932d9aca5ecdca6776b forward (i.e., reverting 369ce54bb302f209239b8ebc77ad824add9df089) with fixed CMakeLists.txt.
2022-06-05 09:11:43 +02:00
Mehdi Amini
369ce54bb3 Revert "[MLIR][GPU] Replace fdiv on fp16 with promoted (fp32) multiplication with reciprocal plus one (conditional) Newton iteration."
This reverts commit bcfc0a9051014437b55ab932d9aca5ecdca6776b.

The build is broken with shared library enabled.
2022-06-04 08:35:45 +00:00
Christian Sigg
bcfc0a9051 [MLIR][GPU] Replace fdiv on fp16 with promoted (fp32) multiplication with reciprocal plus one (conditional) Newton iteration.
This is correct for all values, i.e. the same as promoting the division to fp32 in the NVPTX backend. But it is faster (~10% in average, sometimes more) because:

- it performs less Newton iterations
- it avoids the slow path for e.g. denormals
- it allows reuse of the reciprocal for multiple divisions by the same divisor

Test program:
```
#include <stdio.h>
#include "cuda_fp16.h"

// This is a variant of CUDA's own __hdiv which is fast than hdiv_promote below
// and doesn't suffer from the perf cliff of div.rn.fp32 with 'special' values.
__device__ half hdiv_newton(half a, half b) {
  float fa = __half2float(a);
  float fb = __half2float(b);

  float rcp;
  asm("{rcp.approx.ftz.f32 %0, %1;\n}" : "=f"(rcp) : "f"(fb));

  float result = fa * rcp;
  auto exponent = reinterpret_cast<const unsigned&>(result) & 0x7f800000;
  if (exponent != 0 && exponent != 0x7f800000) {
    float err = __fmaf_rn(-fb, result, fa);
    result = __fmaf_rn(rcp, err, result);
  }

  return __float2half(result);
}

// Surprisingly, this is faster than CUDA's own __hdiv.
__device__ half hdiv_promote(half a, half b) {
  return __float2half(__half2float(a) / __half2float(b));
}

// This is an approximation that is accurate up to 1 ulp.
__device__ half hdiv_approx(half a, half b) {
  float fa = __half2float(a);
  float fb = __half2float(b);

  float result;
  asm("{div.approx.ftz.f32 %0, %1, %2;\n}" : "=f"(result) : "f"(fa), "f"(fb));
  return __float2half(result);
}

__global__ void CheckCorrectness() {
  int i = threadIdx.x + blockIdx.x * blockDim.x;
  half x = reinterpret_cast<const half&>(i);
  for (int j = 0; j < 65536; ++j) {
    half y = reinterpret_cast<const half&>(j);
    half d1 = hdiv_newton(x, y);
    half d2 = hdiv_promote(x, y);
    auto s1 = reinterpret_cast<const short&>(d1);
    auto s2 = reinterpret_cast<const short&>(d2);
    if (s1 != s2) {
      printf("%f (%u) / %f (%u), got %f (%hu), expected: %f (%hu)\n",
             __half2float(x), i, __half2float(y), j, __half2float(d1), s1,
             __half2float(d2), s2);
      //__trap();
    }
  }
}

__device__ half dst;

__global__ void ProfileBuiltin(half x) {
  #pragma unroll 1
  for (int i = 0; i < 10000000; ++i) {
    x = x / x;
  }
  dst = x;
}

__global__ void ProfilePromote(half x) {
  #pragma unroll 1
  for (int i = 0; i < 10000000; ++i) {
    x = hdiv_promote(x, x);
  }
  dst = x;
}

__global__ void ProfileNewton(half x) {
  #pragma unroll 1
  for (int i = 0; i < 10000000; ++i) {
    x = hdiv_newton(x, x);
  }
  dst = x;
}

__global__ void ProfileApprox(half x) {
  #pragma unroll 1
  for (int i = 0; i < 10000000; ++i) {
    x = hdiv_approx(x, x);
  }
  dst = x;
}

int main() {
  CheckCorrectness<<<256, 256>>>();
  half one = __float2half(1.0f);
  ProfileBuiltin<<<1, 1>>>(one);  // 1.001s
  ProfilePromote<<<1, 1>>>(one);  // 0.560s
  ProfileNewton<<<1, 1>>>(one);   // 0.508s
  ProfileApprox<<<1, 1>>>(one);   // 0.304s
  auto status = cudaDeviceSynchronize();
  printf("%s\n", cudaGetErrorString(status));
}
```

Reviewed By: herhut

Differential Revision: https://reviews.llvm.org/D126158
2022-06-04 08:03:29 +02:00
Christian Sigg
544d6507ba [MLIR][NVVM] NFC: add labels to test functions.
Reviewed By: ftynse

Differential Revision: https://reviews.llvm.org/D126631
2022-05-30 10:39:44 +02:00