[LLVMdev] [REQUEST FOR FEEDBACK] Inline asm multiple alternative constraints

Wed Sep 1 11:03:51 PDT 2010

I'm close to confirming that I get the equivalent results from the
test-suite with my changes, compared to a fresh tree, on a Linux x86 64
bit box.

When that is the case, may I check in my current changes for the LLVM side?

My preference is to develop the mult-alt support incrementally, rather than
one big check-in, as I get nervous sitting on a lot of changes for a long
time.

I feel this is relatively safe because the functional change only kicks in
if the new '|' delimiter is seen in the constraints.  Otherwise there should
be no change in behavior.
-John
On Mon, Aug 30, 2010 at 3:34 PM, Dale Johannesen <dalej at apple.com> wrote:

>
>  On Aug 30, 2010, at 3:11 PMPDT, John Thompson wrote:
>
>  Dale,
>
> I took a closer look at the first llc failure, initp1.  Looking at the
> initp1.llc file in gdb, it appears that the statically constructed objects
> without the init_priority attribute are being constructed before those with
> it, though the test seems to expect the opposite.
>
> The initp1.llc.s file seems to have the .ctors table in the right order,
> but the _init code is reading the table in reverse order.  Since I guess the
> init code is coming from the local startup module, this must be a
> peculiarity of Linux x86, right?
>
>
> I don't know, you'll have to get help from somebody who uses Linux.
>
>  Is it different on other platforms?
> Anyway, it was a good exercise for to see how the tests are run, and and to
> dust off my gdb and Linux brain cells.  Is there a prefered platform to run
> the test-suite on, where they all pass?  Or is there a test output file I
> can compare against?
>
>
> llvm changes very quickly and at any given moment some tests might be
> broken on some platforms.  Regressions are usually fixed quickly, though.
>  Darwin x86-{32/64} gets the most attention.
>
>   Thanks.
>
> -John
>
> On Mon, Aug 30, 2010 at 11:10 AM, Dale Johannesen <dalej at apple.com> wrote:
>
>> CBE is fairly broken everywhere AFAIK, don't worry about it.
>> Most of the JIT failures are in tests that exercise exception handling.
>>  Not sure if that is supposed to work in your environment, it works in some
>> JITs and not others.
>> The LLC failures are cause for concern.
>>
>>    On Aug 30, 2010, at 10:59 AMPDT, John Thompson wrote:
>>
>>   Dale,
>>
>> Thanks for reviewing this.
>>
>> I have some newbie questions regarding the test-suite for you or anyone:
>>
>> I'm trying to run the test-suite as described in the "LLVM Testing
>> Infrastructure Guide" on a Ubuntu x86 64 bit system.  Initially I ran into
>> problems with missing tools like yacc, which I fixed as I went along until
>> the make at the test-suite level completed.  However, I get a number of
>> failed tests:
>>
>> john at john-ubuntu:~/llvm/projects/test-suite$ grep FAILED\! jttestlog.txt
>> ******************** TEST (jit) 'tls' FAILED! ********************
>> ******************** TEST (llc) 'initp1' FAILED! ********************
>> ******************** TEST (cbe) 'initp1' FAILED! ********************
>> ******************** TEST (cbe) 'ctor_dtor_count-2' FAILED!
>> ********************
>> ******************** TEST (cbe) 'ctor_dtor_count' FAILED!
>> ********************
>> ******************** TEST (cbe) 'exception_spec_test' FAILED!
>> ********************
>> ******************** TEST (cbe) 'function_try_block' FAILED!
>> ********************
>> ******************** TEST (cbe) 'simple_rethrow' FAILED!
>> ********************
>> ******************** TEST (cbe) 'simple_throw' FAILED!
>> ********************
>> ******************** TEST (cbe) 'throw_rethrow_test' FAILED!
>> ********************
>> ******************** TEST (jit) 'ctor_dtor_count-2' FAILED!
>> ********************
>> ******************** TEST (jit) 'ctor_dtor_count' FAILED!
>> ********************
>> ******************** TEST (jit) 'exception_spec_test' FAILED!
>> ********************
>> ******************** TEST (jit) 'function_try_block' FAILED!
>> ********************
>> ******************** TEST (jit) 'simple_rethrow' FAILED!
>> ********************
>> ******************** TEST (jit) 'simple_throw' FAILED!
>> ********************
>> ******************** TEST (jit) 'throw_rethrow_test' FAILED!
>> ********************
>> ******************** TEST (cbe) '2004-03-15-IndirectGoto' FAILED!
>> ********************
>> ******************** TEST (cbe) 'except' FAILED! ********************
>> ******************** TEST (jit) 'except' FAILED! ********************
>> ******************** TEST (cbe) 'bigfib' FAILED! ********************
>> ******************** TEST (llc) 'spirit' FAILED! ********************
>> ******************** TEST (cbe) 'spirit' FAILED! ********************
>> ******************** TEST (jit) 'spirit' FAILED! ********************
>> ******************** TEST (cbe) 'burg' FAILED! ********************
>> ******************** TEST (cbe) 'sgefa' FAILED! ********************
>> ******************** TEST (cbe) 'make_dparser' FAILED!
>> ********************
>> ******************** TEST (jit) 'spiff' FAILED! ********************
>> ******************** TEST (cbe) 'oggenc' FAILED! ********************
>> ******************** TEST (cbe) 'lencod' FAILED! ********************
>> ******************** TEST (cbe) 'SIBsim4' FAILED! ********************
>> ******************** TEST (llc) 'clamscan' FAILED! ********************
>> ******************** TEST (cbe) 'clamscan' FAILED! ********************
>> ******************** TEST (jit) 'clamscan' FAILED! ********************
>> ******************** TEST (cbe) 'sqlite3' FAILED! ********************
>> ******************** TEST (jit) 'lemon' FAILED! ********************
>> ******************** TEST (cbe) 'OpenSSL' FAILED! ********************
>> ******************** TEST (jit) 'OpenSSL' FAILED! ********************
>> ******************** TEST (cbe) 'minisat' FAILED! ********************
>> ******************** TEST (jit) 'minisat' FAILED! ********************
>> ******************** TEST (cbe) 'lua' FAILED! ********************
>> ******************** TEST (cbe) 'Obsequi' FAILED! ********************
>> ******************** TEST (cbe) 'kc' FAILED! ********************
>> ******************** TEST (cbe) 'fhourstones3.1' FAILED!
>> ********************
>> ******************** TEST (cbe) 'bh' FAILED! ********************
>> ******************** TEST (cbe) 'health' FAILED! ********************
>> ******************** TEST (cbe) 'cfrac' FAILED! ********************
>> ******************** TEST (cbe) 'espresso' FAILED! ********************
>> ******************** TEST (cbe) 'gs' FAILED! ********************
>> ******************** TEST (cbe) 'agrep' FAILED! ********************
>> ******************** TEST (cbe) 'archie' FAILED! ********************
>> ******************** TEST (cbe) 'unix-smail' FAILED! ********************
>> ******************** TEST (cbe) 'rawcaudio' FAILED! ********************
>> ******************** TEST (cbe) 'rawdaudio' FAILED! ********************
>> ******************** TEST (cbe) 'encode' FAILED! ********************
>> ******************** TEST (cbe) 'mpeg2decode' FAILED! ********************
>> ******************** TEST (cbe) 'consumer-lame' FAILED!
>> ********************
>> ******************** TEST (cbe) 'consumer-typeset' FAILED!
>> ********************
>> ******************** TEST (cbe) 'office-ispell' FAILED!
>> ********************
>> ******************** TEST (cbe) 'telecomm-fft' FAILED!
>> ********************
>> ******************** TEST (cbe) 'enc-3des' FAILED! ********************
>> ******************** TEST (cbe) 'enc-pc1' FAILED! ********************
>> ******************** TEST (cbe) 'enc-rc4' FAILED! ********************
>> ******************** TEST (cbe) 'tramp3d-v4' FAILED! ********************
>> ******************** TEST (cbe) 'bullet' FAILED! ********************
>>
>> At this point I'm not sure if its because I'm still missing tools, these
>> errors are expected on this platform, or there's some problem with my tree.
>> Any suggestions?
>>
>> -John
>>
>> On Thu, Aug 26, 2010 at 7:23 PM, Dale Johannesen <dalej at apple.com> wrote:
>>
>>>
>>> On Aug 25, 2010, at 12:45 PM, John Thompson wrote:
>>>
>>> Hi,
>>>>
>>>> I'm looking for some feedback on the changes represented in the attached
>>>> patches, which I'll describe below.
>>>>
>>>> I'm sending this to both the LLVM and Clang list because it affects
>>>> both, though the main focus here is LLVM.
>>>> Basically, I've partially implemented some changes for choosing multiple
>>>> alternative constraints largely on the LLVM side.
>>>>
>>>> The Clang change is to output the multiple constraints using a '|'
>>>> character in the constraint strings to delimit the alternatives.
>>>>
>>>
>>> This part is simple, and it can't be worse than it is now.
>>>
>>>
>>> The LLVM change is as follows.
>>>>
>>>> In an earlier attempt, I just hacked up
>>>> SelectionDAGBuilder::visitInlineAsm, and pretty much used the same logic in
>>>> TargetLowering::ComputeConstraintToUse/ChooseConstraint.  But then I
>>>> discovered that InlineAsm::ParseConstraints was called in a couple of other
>>>> places, and in one of those places (IsOperandAMemoryOperand in
>>>> AddrModeMatcher.cpp), there wasn't a DAG pointer handy (at least I don't
>>>> think there is, as I'm not too familiar yet with LLVM internals), which
>>>> meant that I needed to handle multiple alternative constraints in other
>>>> places besides just SelectionDAGBuilder::visitInlineAsm.
>>>>
>>>
>>> That's too bad, I didn't know about the AddrModeMatcher reference.  I
>>> don't see a DAG pointer either; it seems to be an argument in some places.
>>>  Regardless,  unifying the three loops that do pretty much the same thing is
>>> surely a good idea.
>>>
>>>
>>>  Basically I see that there are three layers of contraint info classes,
>>>> SDISelAsmOperandInfo -> AsmOperandInfo -> ConstraintInfo.  Therefore, I
>>>> implemented a different scheme, putting a ParseConstraints function in
>>>> TargetLowering that returns a vector of AsmOperandInfo objects, and which
>>>> will do the constraint selection without needing the DAG.  I'm assuming the
>>>> value info in the operands from the callsite object is sufficient to choose
>>>> the constraints.  I also added some other virtual functions to
>>>> TargetLowering to allow the different targets to handle the target-specific
>>>> contraints.  At present, I only overrode the getSingleConstraintMatchWeight
>>>> function in X86TargetLowering, and just for one constraint letter, as an
>>>> example.
>>>>
>>>> In the three places where the original InlineAsm::ParseConstraints was
>>>> called (CodeGenPrepare.cpp, AddrModeMatcher.cpp, and SelectionDAGBuilder), I
>>>> replaced the calls with calls to TargetLowering::ParseConstraints, and
>>>> revised the loops over the constraints accordingly, which were still needed
>>>> to set up SDISelAsmOperandInfo objects or get other information the code was
>>>> looking for.  SelectionDAGBuilder::visitInlineAsm I especially reordered bit
>>>> at the front, to make things work.  I left in a little bit of overlap in the
>>>> setting of the CallOperandVal member in the first for loop, which I could
>>>> factor out, as I really just need the output and input counts.
>>>>
>>>> Bascially, I wanted to get some feedback before I went too much farther
>>>> down this road.
>>>>
>>>
>>> I don't have that good a sense of good class design, but this looks OK to
>>> me.
>>>
>>>
>>> I think the main work left is to add support for all or some subset of
>>>> both the generic and target-specific constraints, and to write tests for
>>>> them all.
>>>>
>>>> Since I had trouble with running tests on a Windows box, I set up a
>>>> Linux box so I could run the regression tests.  The tests still pass with
>>>> these changes.
>>>>
>>>
>>> Those tests don't include any for multiple alternative constraints, since
>>> the expectation is the llvm-gcc FE will have removed them.  You should
>>> really run the gcc testsuite as well; that's a much better test of inline
>>> asm.  If you get this working right there should be some new passes.  I'm
>>> not sure how to run it using clang as the compiler, but I think Daniel got
>>> it to work.
>>>
>>>
>>> So, my main question is, am I on the right track?  And either way,
>>>> specific information on problems would be appreciated too.
>>>>
>>>> Another question concerns the weighting I used for choosing the
>>>> constraints.  Bascially I pretty much used the same prioritization used in
>>>> TargetLowering::ComputeConstraintToUse/ChooseConstraint, which will chose
>>>> memory operands over register.  I would have thought a register operand
>>>> would have been a better choice over memory, but then that raises the
>>>> question of whether you can know what's already in a register when this
>>>> instruction is reached.  I haven't gotten deep enough to know yet.  I assume
>>>> it's like this because it is more likely to be a correct fit, if not
>>>> optimal.
>>>>
>>>
>>> I think it's that it's possible to run out of registers if you pick "r"
>>> for a large number of "rm" constraints.  This mainly affects asm blocks,
>>> where you have hundreds of lines of asm in a single statement.
>>>
>>>
>>> It seems that if the value info in the operands from the callsite object
>>>> is sufficient to choose the constraints, the
>>>> ComputeConstraintToUse/ChooseConstraint function could also use this scheme,
>>>> probably just calling the same get weight functions, to be a bit more
>>>> efficient.  I left it alone for now, because I know it works as it is.
>>>>
>>>
>>> Thanks for working on this.
>>>
>>>
>>>
>>
>>
>> --
>> John Thompson
>> John.Thompson.JTSoftware at gmail.com
>>
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>>
>>
>>
>
>
> --
> John Thompson
> John.Thompson.JTSoftware at gmail.com
>
> _______________________________________________
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> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
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>
>
>

-- 
John Thompson
John.Thompson.JTSoftware at gmail.com
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