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Commit Graph

193275 Commits

Author SHA1 Message Date
Matt Arsenault
997e59690c AMDGPU: Directly annotate functions if they have calls
Currently we infer whether the flat-scratch-init kernel input should
be enabled based on calls. Move this handling, so we can decide if the
full set of ABI inputs is needed in kernels. Ideally we would have an
analysis of some sort, rather than the function attributes.
2020-03-12 19:10:59 -04:00
Matt Arsenault
d824eb8a0e CodeGen: Add constexpr to Register constructors 2020-03-12 19:10:59 -04:00
Lang Hames
2e64fe9bf7 [ORC] Enable exception handling in JIT'd code when using LLJIT on Darwin.
This patch enables exception handling in code added to LLJIT on Darwin by
adding an orc::EHFrameRegistrationPlugin instance to the ObjectLinkingLayer
(which is currently used on Darwin only).
2020-03-12 15:33:56 -07:00
Lang Hames
a043ecbcf2 [ORC] Add a mutex to guard EHFrameRegistrationPlugin data structures.
These may be accessed from multiple threads if concurrent materialization is
enabled in ORC.

Testcase coming in a follow-up patch that enables eh-frame registration for
LLJIT.
2020-03-12 15:33:56 -07:00
Stanislav Mekhanoshin
10ac6dbf1b [AMDGPU] Simplify exec copies
The patch removes late endcf handling and only leaves the
related portion with redundant exec mask copy elimination.

Differential Revision: https://reviews.llvm.org/D76095
2020-03-12 14:54:19 -07:00
Huihui Zhang
58a931b286 [SVE] Update API ConstantVector::getSplat() to use ElementCount.
Summary:
Support ConstantInt::get() and Constant::getAllOnesValue() for scalable
vector type, this requires ConstantVector::getSplat() to take in 'ElementCount',
instead of 'unsigned' number of element count.

This change is needed for D73753.

Reviewers: sdesmalen, efriedma, apazos, spatel, huntergr, willlovett

Reviewed By: efriedma

Subscribers: tschuett, hiraditya, rkruppe, psnobl, cfe-commits, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74386
2020-03-12 13:22:41 -07:00
Simon Pilgrim
1210ccd8d7 [AMDGPU] Add ISD::FSHR -> ALIGNBIT support
This patch allows ISD::FSHR(i32) patterns to lower to ALIGNBIT instructions.

This improves test coverage of ISD::FSHR matching - x86 has both FSHL/FSHR instructions and we prefer FSHL by default.

Differential Revision: https://reviews.llvm.org/D76070
2020-03-12 20:16:57 +00:00
Simon Pilgrim
ae51b83e4a [DAGCombine] foldVSelectOfConstants - ensure constants are same type
Fix bug identified by https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=21167, foldVSelectOfConstants must ensure that the 2 build vectors have scalars of the same type before trying to compare APInt values.
2020-03-12 20:02:05 +00:00
Thomas Lively
267661cd96 [WebAssembly] Fix SIMD shift unrolling to avoid assertion failure
Summary:
Using the default DAG.UnrollVectorOp on v16i8 and v8i16 vectors
results in i8 or i16 nodes being inserted into the SelectionDAG. Since
those are illegal types, this causes a legalization assertion failure
for some code patterns, as uncovered by PR45178. This change unrolls
shifts manually to avoid this issue by adding and using a new optional
EVT argument to DAG.ExtractVectorElements to control the type of the
extract_element nodes.

Reviewers: aheejin, dschuff

Subscribers: sbc100, jgravelle-google, hiraditya, sunfish, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76043
2020-03-12 12:20:14 -07:00
David Green
29af250985 [ARM] Long shift tests. NFC 2020-03-12 19:01:49 +00:00
Simon Pilgrim
8136e699ee ExecutionDomainFix - fix static analyzer out of range shift warnings.
Repeat the assertion that we already have in hasDomain for addDomain and setSingleDomain.
2020-03-12 18:52:56 +00:00
Florian Hahn
f18b2707d7 Revert "[SCCP] Use ValueLatticeElement instead of LatticeVal (NFCI)"
This commit is likely causing clang-with-lto-ubuntu to fail
http://lab.llvm.org:8011/builders/clang-with-lto-ubuntu/builds/16052

Also causes PR45185.

This reverts commit f1ac5d2263f8419b865cc78ba1f5c8694970fb6b.
2020-03-12 18:49:11 +00:00
Stanislav Mekhanoshin
8e802d9c40 [AMDGPU] Simplify nested SI_END_CF
This is to replace the optimization from the SIOptimizeExecMaskingPreRA.
We have less opportunities in the control flow lowering because many
VGPR copies are still in place and will be removed later, but we know
for sure an instruction is SI_END_CF and not just an arbitrary S_OR_B64
with EXEC.

The subsequent change needs to convert s_and_saveexec into s_and and
address new TODO lines in tests, then code block guarded by the
-amdgpu-remove-redundant-endcf option in the pre-RA exec mask optimizer
will be removed.

Differential Revision: https://reviews.llvm.org/D76033
2020-03-12 11:25:07 -07:00
David Blaikie
4560a0277a CFGDiff: Simplify and generalize over all graph types
Use GraphTraits in the implementation of the GraphDiff's own GraphTraits
so GraphDiff can be used across all graph types that provide
GraphTraits.

Also use partial template specializations to make the traits a bit more
compact.

Reviewers: asbirlea

Differential Revision: https://reviews.llvm.org/D76034
2020-03-12 10:45:45 -07:00
LLVM GN Syncbot
4ec020163d [gn build] Port fa8080376e7 2020-03-12 16:33:39 +00:00
LLVM GN Syncbot
60938ca48c [gn build] Port 2c9cf9f4ddd 2020-03-12 16:01:56 +00:00
Zarko Todorovski
cce8e6c4f2 [PowerPC][AIX] Implement formal arguments passed in stack memory.
This patch is the callee side counterpart for https://reviews.llvm.org/D73209.
It removes the fatal error when we pass more formal arguments than available
registers.

Differential Revision: https://reviews.llvm.org/D74225
2020-03-12 11:48:00 -04:00
Hideto Ueno
ff4b2bbc49 [Attributor][FIX] Add a missing dependence track in noalias deduction 2020-03-12 15:27:35 +00:00
Marcello Maggioni
b601dcbed2 [RAGreedy] Fix minor typo in comment. NFC 2020-03-12 08:15:04 -07:00
Xiangling Liao
108e0aed3c [PowerPC32] Fix the setcc inconsistent result type problem
Summary:
On 32-bit PPC target[AIX and BE], when we convert an `i64` to `f32`, a `setcc` operand expansion is needed. The expansion will set the result type of expanded `setcc` operation based on if the subtarget use CRBits or not. If the subtarget does use the CRBits, like AIX and BE, then it will set the result type to `i1`, leading to an inconsistency with original `setcc` result type[i32].
And the reason why it crashed underneath is because we don't set result type of setcc consistent in those two places.

This patch fixes this problem by setting original setcc opnode result type also with `getSetCCResultType`  interface.

Reviewers: sfertile, cebowleratibm, hubert.reinterpretcast, Xiangling_L

Reviewed By: sfertile

Subscribers: wuzish, nemanjai, hiraditya, kbarton, jsji, shchenz, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75702
2020-03-12 10:50:37 -04:00
Simon Moll
48bf9cf2dc [VE][nfc] Use RRIm for RRINDm, remove the latter
Summary:
De-duplicate isel instruction classes by using RRIm for RRINDm. The latter
becomes obsolete.

Reviewed By: arsenm

Differential Revision: https://reviews.llvm.org/D76063
2020-03-12 15:38:07 +01:00
Sean Fertile
5c20469fda [PowerPC][AIX] Fix printing of program counter for AIX assembly.
Program counter on AIX is the dollar-sign.

Differential Revision:https://reviews.llvm.org/D75627
2020-03-12 10:37:18 -04:00
Andrzej Warzynski
df7173628b [AArch64][SVE] Add intrinsics for non-temporal scatters/gathers
Summary:
This patch adds the following intrinsics for non-temporal gather loads
and scatter stores:
  * aarch64_sve_ldnt1_gather_index
  * aarch64_sve_stnt1_scatter_index
These intrinsics implement the "scalar + vector of indices" addressing
mode.

As opposed to regular and first-faulting gathers/scatters, there's no
instruction that would take indices and then scale them. Instead, the
indices for non-temporal gathers/scatters are scaled before the
intrinsics are lowered to `ldnt1` instructions.

The new ISD nodes, GLDNT1_INDEX and SSTNT1_INDEX, are only used as
placeholders so that we can easily identify the cases implemented in
this patch in performGatherLoadCombine and performScatterStoreCombined.
Once encountered, they are replaced with:
  * GLDNT1_INDEX -> SPLAT_VECTOR + SHL + GLDNT1
  * SSTNT1_INDEX -> SPLAT_VECTOR + SHL + SSTNT1

The patterns for lowering ISD::SHL for scalable vectors (required by
this patch) were missing, so these are added too.

Reviewed By: sdesmalen

Differential Revision: https://reviews.llvm.org/D75601
2020-03-12 13:55:56 +00:00
Sanjay Patel
e208d8fad2 [InstSimplify] simplify FP ops harder with FMF (part 2)
This is part of the IR sibling for:
D75576

Related transform committed with:
rG8ec71585719d
2020-03-12 09:53:20 -04:00
Sanjay Patel
49fae1d6d3 [InstSimplify] simplify FP ops harder with FMF
This is part of the IR sibling for:
D75576

(I'm splitting part of the transform as a separate commit
to reduce risk. I don't know of any bugs that might be
exposed by this improved folding, but it's hard to see
those in advance...)
2020-03-12 09:13:28 -04:00
Simon Pilgrim
9c844506db [X86] Add FeatureFast7ByteNOP flag
Lets us remove another SLM proc family flag usage.

This is NFC, but we should probably check whether atom/glm/knl? should be using this flag as well...
2020-03-12 13:06:43 +00:00
Simon Pilgrim
cff27005be [AMDGPU] Add some funnel shift intrinsic test coverage 2020-03-12 12:53:57 +00:00
Sanjay Patel
6f2eb1ac3c [InstSimplify] reduce code for FP undef/nan folding; NFC 2020-03-12 08:46:15 -04:00
Nico Weber
72bedfa080 Use grep -F instead of deprecated fgrep.
(In addition to the deprecation bit, this is useful on Windows
where people might have grep but not fgrep.)
2020-03-12 08:34:38 -04:00
Sanjay Patel
630a1a6c67 [InstSimplify] add tests for FP poison; NFC
Adapted from codegen tests seen in D75576.
2020-03-12 08:32:04 -04:00
Florian Hahn
b4dc084389 [SCCP] Use ValueLatticeElement instead of LatticeVal (NFCI)
This patch switches SCCP to use ValueLatticeElement for lattice values,
instead of the local LatticeVal, as first step to enable integer range support.

This patch does not make use of constant ranges for additional operations
and the only difference for now is that integer constants are represented by
single element ranges. To preserve the existing behavior, the following helpers
are used

* isConstant(LV): returns true when LV is either a constant or a constant range with a single element. This should return true in the same cases where LV.isConstant() returned true previously.
* getConstant(LV): returns a constant if LV is either a constant or a constant range with a single element. This should return a constant in the same cases as LV.getConstant() previously.
* getConstantInt(LV): same as getConstant, but additionally casted to ConstantInt.

Reviewers: davide, efriedma, mssimpso

Reviewed By: efriedma

Differential Revision: https://reviews.llvm.org/D60582
2020-03-12 12:03:06 +00:00
LLVM GN Syncbot
b4cde323ef [gn build] Port d5edcb90643 2020-03-12 11:58:14 +00:00
Dylan McKay
895b12059d [AVR] Fix reads of uninitialized variables from constructor of AVRSubtarget
The initialization order was not correct. These bugs were discovered by
valgrind. They appear to work fine in practice but this patch should
unblock switching the AVR backend on by default as now a standard AVR
llc invocation runs without memory errors.

The AVRISelLowering constructor would run before the subtarget boolean
fields were initialized to false. Now, the initialization order is
correct.
2020-03-13 00:57:19 +13:00
Simon Pilgrim
89f4b30257 [X86] combineOrShiftToFunnelShift - remove shift by immediate handling.
Now that D75114 has landed, DAGCombiner handles this case so the code is redundant.
2020-03-12 11:46:51 +00:00
Simon Tatham
92a8f6251f [ARM,MVE] Add intrinsics and isel for MVE fused multiply-add.
Summary:
This adds the ACLE intrinsic family for the VFMA and VFMS
instructions, which perform fused multiply-add on vectors of floats.

I've represented the unpredicated versions in IR using the cross-
platform `@llvm.fma` IR intrinsic. We already had isel rules to
convert one of those into a vector VFMA in the simplest possible way;
but we didn't have rules to detect a negated argument and turn it into
VFMS, or rules to detect a splat argument and turn it into one of the
two vector/scalar forms of the instruction. Now we have all of those.

The predicated form uses a target-specific intrinsic as usual, but
I've stuck to just one, for a predicated FMA. The subtraction and
splat versions are code-generated by passing an fneg or a splat as one
of its operands, the same way as the unpredicated version.

In arm_mve_defs.h, I've had to introduce a tiny extra piece of
infrastructure: a record `id` for use in codegen dags which implements
the identity function. (Just because you can't declare a Tablegen
value of type dag which is //only// a `$varname`: you have to wrap it
in something. Now I can write `(id $varname)` to get the same effect.)

Reviewers: dmgreen, MarkMurrayARM, miyuki, ostannard

Reviewed By: dmgreen

Subscribers: kristof.beyls, hiraditya, danielkiss, cfe-commits, llvm-commits

Tags: #clang, #llvm

Differential Revision: https://reviews.llvm.org/D75998
2020-03-12 11:13:50 +00:00
Dylan McKay
c8fcf75f50 [AVR] Fix read of uninitialized variable AVRSubtarget:::ELFArch
Found by the LLVM MemorySanitizer tests when switching AVR to a default
backend.

ELFArch must be initialized before the call to
initializeSubtargetDependencies().

The uninitialized read would occur deep within TableGen'd code.
2020-03-13 00:09:13 +13:00
Max Kazantsev
b1318e4cc2 [LoopPeel] Turn incorrect assert into a check
Summary:
This patch replaces incorrectt assert with a check. Previously it asserts that
if SCEV cannot prove `isKnownPredicate(A != B)`, then it should be able to prove
`isKnownPredicate(A == B)`.

Both these fact may be not provable. It is shown in the provided test:

Could not prove: `{-294,+,-2}<%bb1> !=  0`
Asserting: `{-294,+,-2}<%bb1> == 0`

Obviously, this SCEV is not equal to zero, but 0 is in its range so we cannot
also prove that it is not zero.

Instead of assert, we should be checking the required conditions explicitly.

Reviewers: lebedev.ri, fhahn, sanjoy, fedor.sergeev
Reviewed By: lebedev.ri
Subscribers: hiraditya, zzheng, javed.absar, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D76050
2020-03-12 17:23:07 +07:00
Tyker
43346d7e59 Basis of dropping uses in llvm.assume.
Summary: This patch adds the basic utilities to deal with dropable uses. dropable uses are uses that we rather drop than prevent transformations, for now they are limited to uses in llvm.assume.

Reviewers: jdoerfert, sstefan1

Reviewed By: jdoerfert

Subscribers: uenoku, lebedev.ri, mgorny, hiraditya, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D73404
2020-03-12 10:10:22 +01:00
Tyker
eda3bf5428 [NFC] Add filters to hasNItems and hasNItemsOrMore
Reviewers: lebedev.ri, jdoerfert

Reviewed By: jdoerfert

Subscribers: jdoerfert, dexonsmith, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D74967
2020-03-12 10:10:21 +01:00
Qiu Chaofan
4a773960a6 [PowerPC] Add strict-fp intrinsic to FP arithmetic
This patch adds basic strict-fp intrinsics support to PowerPC backend,
including basic arithmetic operations (add/sub/mul/div).

Reviewed By: steven.zhang, andrew.w.kaylor

Differential Revision: https://reviews.llvm.org/D63916
2020-03-12 17:02:54 +08:00
Roman Lebedev
f6c10d3f93 [SCEV] isHighCostExpansionHelper(): use correct TTI hooks
Summary:
Cost modelling strikes again.
In PR44668 <https://bugs.llvm.org/show_bug.cgi?id=44668> patch series,
i've made the same mistake of always using generic `getOperationCost()`
that i missed in reviewing D73480/D74495 which was later fixed
in 62dd44d76da9aa596fb199bda8b1e8768bb41033.

We should be using more specific hooks instead - `getCastInstrCost()`,
`getArithmeticInstrCost()`, `getCmpSelInstrCost()`.

Evidently, this does not have an effect on the existing testcases,
with unchanged default cost budget. But if it *does* have an effect
on some target, we'll have to segregate tests that use this function
per-target, much like we already do with other TTI-aware transform tests.

There's also an issue that @samparker has brought up in post-commit-review:
>>! In D73501#1905171, @samparker wrote:
> Hi,
> Did you get performance numbers for these patches? We track the performance
> of our (Arm) open source DSP library and the cost model fixes were generally
> a notable improvement, so many thanks for that! But the final patch
> for rewriting exit values has generally been bad, especially considering
> the gains from the modelling improvements. I need to look into it further,
> but on my current test case I'm seeing +30% increase in stack accesses
> with a similar decrease in performance.
> I'm just wondering if you observed any negative effects yourself?

I don't know if this addresses that, or we need D66450 for that.

Reviewers: samparker, spatel, mkazantsev, reames, wmi

Reviewed By: reames

Subscribers: kristof.beyls, hiraditya, danielkiss, llvm-commits, samparker

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75908
2020-03-12 11:33:38 +03:00
Dominik Montada
a43ec896ff [GlobalISel] fix crash in narrowScalarExtract if DstRegs only has one register
Summary: When narrowing a scalar G_EXTRACT where the destination lines up perfectly with a single result of the emitted G_UNMERGE_VALUES a COPY should be emitted instead of unconditionally trying to emit a G_MERGE_VALUES.

Reviewers: arsenm, dsanders

Reviewed By: arsenm

Subscribers: wdng, rovka, hiraditya, volkan, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75743
2020-03-12 09:14:35 +01:00
Sebastian Neubauer
99d5e9179e [AMDGPU] Use progbits type for .AMDGPU.disasm section
The note section type implies a specific format that this section does
not have thus tools like readelf fail here. Progbits has no format and
another pipeline compiler already sets the type to progbits.

Differential Revision: https://reviews.llvm.org/D75913
2020-03-12 09:08:11 +01:00
Clement Courbet
295a588a31 [ExpandMemCmp][NFC] Add more tests. 2020-03-12 08:49:51 +01:00
Tres Popp
d71aadd4c9 Remove unused variable.
Delete dead code from 8fffa40400e8719222e7f67152c12738521fa9fb.
2020-03-12 08:42:57 +01:00
Shengchen Kan
bd3955496d [X86] Reduce the number of emitted fragments due to branch align
Summary:
Currently, a BoundaryAlign fragment may be inserted after the branch
that needs to be aligned to truncate the current fragment, this fragment is
unused at most of time. To avoid that, we can insert a new empty Data
fragment instead. Non-relaxable instruction is usually emitted into Data
fragment, so the inserted empty Data fragment will be reused at a high
possibility.

Reviewers: annita.zhang, reames, MaskRay, craig.topper, LuoYuanke, jyknight

Reviewed By: reames, LuoYuanke

Subscribers: llvm-commits, dexonsmith, hiraditya

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75438
2020-03-12 15:37:35 +08:00
Juneyoung Lee
0e2e85de2b Apply update_test_check.py to CodeGenPrepare/X86/freeze-icmp.ll test 2020-03-12 16:37:16 +09:00
Djordje Todorovic
21053795f1 [DebugInfo] Fix build failure on the mingw
Add the workaround for the X86::MOV16ri when describing call site
parameters.
2020-03-12 08:18:01 +01:00
Dylan McKay
661d0f01ba Revert "[AVR] Include AVR by default in LLVM builds"
This reverts commit dfecec65e6796c075aebe50e88260a33aa2efd06.

Merging the change revealed that there is a failure on the memory
sanitizer bots.

    Command Output (stderr):
    --
    ==3569==WARNING: MemorySanitizer: use-of-uninitialized-value
        #0 0x1d71bff in
           llvm::AVRSubtarget::ParseSubtargetFeatures(llvm::StringRef,
    llvm::StringRef)
    /b/sanitizer-x86_64-linux-fast/build/llvm_build_msan/lib/Target/AVR/AVRGenSubtargetInfo.inc:471:7
        #1 0x1d721f8 in initializeSubtargetDependencies
           /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/lib/Target/AVR/AVRSubtarget.cpp:50:3
        #2 0x1d721f8 in llvm::AVRSubtarget::AVRSubtarget(llvm::Triple
           const&, std::__1::basic_string<char, std::__1::char_traits<char>,
    std::__1::allocator<char> > const&, std::__1::basic_string<char,
    std::__1::char_traits<char>, std::__1::allocator<char> > const&,
    llvm::AVRTargetMachine const&)
    /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/lib/Target/AVR/AVRSubtarget.cpp:33:18
        #3 0x1d3077f in
           llvm::AVRTargetMachine::AVRTargetMachine(llvm::Target const&,
    llvm::Triple const&, llvm::StringRef, llvm::StringRef,
    llvm::TargetOptions const&, llvm::Optional<llvm::Reloc::Model>,
    llvm::Optional<llvm::CodeModel::Model>, llvm::CodeGenOpt::Level, bool)
    /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/lib/Target/AVR/AVRTargetMachine.cpp:52:7
        #4 0x1d3169d in
           llvm::RegisterTargetMachine<llvm::AVRTargetMachine>::Allocator(llvm::Target
    const&, llvm::Triple const&, llvm::StringRef, llvm::StringRef,
    llvm::TargetOptions const&, llvm::Optional<llvm::Reloc::Model>,
    llvm::Optional<llvm::CodeModel::Model>, llvm::CodeGenOpt::Level, bool)
    /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/include/llvm/Support/TargetRegistry.h:1121:16
        #5 0x86662f in createTargetMachine
           /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/include/llvm/Support/TargetRegistry.h:402:12
        #6 0x86662f in compileModule(char**, llvm::LLVMContext&)
           /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/tools/llc/llc.cpp:473:52
        #7 0x861f42 in main
           /b/sanitizer-x86_64-linux-fast/build/llvm-project/llvm/tools/llc/llc.cpp:356:22
        #8 0x7f76f7b072e0 in __libc_start_main
           (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
        #9 0x7ebbc9 in _start
           (/b/sanitizer-x86_64-linux-fast/build/llvm_build_msan/bin/llc+0x7ebbc9)

    SUMMARY: MemorySanitizer: use-of-uninitialized-value
    /b/sanitizer-x86_64-linux-fast/build/llvm_build_msan/lib/Target/AVR/AVRGenSubtargetInfo.inc:471:7
    in llvm::AVRSubtarget::ParseSubtargetFeatures(llvm::StringRef,
    llvm::StringRef)
    Exiting
    FileCheck error: '<stdin>' is empty.
    --

The patch wiill be re-committed once fixed.
2020-03-12 19:53:46 +13:00
Dylan McKay
1719c58d99 [AVR] Include AVR by default in LLVM builds
Summary:
This patch makes the AVR backend an official target of LLVM, serving
as a request for comments for moving the AVR backend out of
experimental.

A future patch will move the LLVM AVR buildbot (llvm-avr-linux) from the
staging buildmaster to the production buildmaster, so error emails will
start to go out.

Summary of the backend
----------------------

  - 16-bit little endian
  - AsmParser based assembly parser
  - uses the MC library for generating AVR ELFs
  - most logic driven from standard TableGen-erated tables like other
    backends
  - passes all of the test suite under `check-all`, including generic
    CodeGen and DebugInfo tests
  - Used in two frontends
  - Limited, but functional support for DebugInfo and LLVM DWARF dumping
  - Binary compatible with AVR-GCC and avr-{libc,libgcc} for the most part
  - Cannot lower 32-bit shifts due to a bug, can lower shifts larger or
    smaller
  - Supports assembly/MC for all the entire AVR ISA, generally generates poorly
    optimized machine instructions, with most focus thus far on correctness

I've added reviewers and subscribers from previous patches where backends were made official,
and those who participated in the recent thread on llvm-dev, please add anybody I've missed.

The most recent discussion on this topic can be found in the llvm-dev thread [Moving the AVR backend out of experimental](https://lists.llvm.org/pipermail/llvm-dev/2020-February/139158.html)

Reviewers: chandlerc, lattner, rengolin, tstellar, arsenm, thakis, simoll, asb

Reviewed By: rengolin, thakis

Subscribers: CryZe, wdng, mgorny, aprantl, Jim, hans, aykevl, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D75099
2020-03-12 19:07:42 +13:00