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

[Tom Stellard]

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, 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?

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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