[llvm-commits] [llvm] r160273 - /llvm/trunk/test/CodeGen/R600/

[Duncan Sands]

Hi Tom,

On 16/07/12 17:54, Tom Stellard wrote:
> On Mon, Jul 16, 2012 at 04:39:37PM +0200, Duncan Sands wrote:
>> Hi Tom, adding a bunch of testcases that diff against binary blobs seems like a
>> really bad idea to me.  Suppose I make a change to codegen and one of these
>> tests breaks.  How am I to understand if the change I made just resulted in an
>> unimportant difference, such as slightly different register allocation, or if
>> I really broke something?
>>
>
> Hi Duncan,
>
> I can see how that would be a problem.  I think the main difficulty here
> is that the R600 backend doesn't have an AsmPrinter,

can it get one?

  so there isn't really
> another way to test the output (unless it's possible to parse the output
> of MF.dump()).
>
> The other issue is that I wasn't quite sure exactly what should be
> tested with these test cases.  I tried to make all test cases I wrote
> compile down to a single instruction, so that they should never change,
> but ideally I would like to add more complex tests cases as well.
> However, my concern with the more complex tests, is that they might be
> "broken" by correct optimizations that changed the output slightly,
> which would confuse the developer implementing the optimization.  How is
> this situation handled with other backends?

They output a textual representation and use FileCheck to check the output,
c.f. the tests for all the other backends in tests/CodeGen.  Since FileCheck
does string matching (possibly with patterns) it is possible, but not always
easy, to check that the aspects you are looking for occurred while ignoring
insignificant details.

Ciao, Duncan.

>
> Up to this point I've been regression testing the backend using Mesa's
> Open Source test suite piglit[1], which provides really good coverage.
> I would like to make better use of the LLVM testing infrastructure, but
> as I mentioned I'm not quite sure the kinds of tests I should be
> writing.
>
> -Tom
>
> [1] http://cgit.freedesktop.org/piglit
>
>> Ciao, Duncan.
>
>>> --- llvm/trunk/test/CodeGen/R600/fadd.ll (added)
>>> +++ llvm/trunk/test/CodeGen/R600/fadd.ll Mon Jul 16 09:17:19 2012
>>> @@ -0,0 +1,15 @@
>>> +;RUN: llc < %s -march=r600 -mcpu=redwood | diff %s.check -
>>> +
>>> +
>>> +define void @test() {
>>> +   %r0 = call float @llvm.R600.load.input(i32 0)
>>> +   %r1 = call float @llvm.R600.load.input(i32 1)
>>> +   %r2 = fadd float %r0, %r1
>>> +   call void @llvm.AMDGPU.store.output(float %r2, i32 0)
>>> +   ret void
>>> +}
>>> +
>>> +declare float @llvm.R600.load.input(i32) readnone
>>> +
>>> +declare void @llvm.AMDGPU.store.output(float, i32)
>>> +
>>>
>>> Added: llvm/trunk/test/CodeGen/R600/fadd.ll.check
>>> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/R600/fadd.ll.check?rev=160273&view=auto
>>> ==============================================================================
>>> Binary files llvm/trunk/test/CodeGen/R600/fadd.ll.check (added) and llvm/trunk/test/CodeGen/R600/fadd.ll.check Mon Jul 16 09:17:19 2012 differ
>> ...
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>