Is this fixed now with the fcmp instruction?

nope. The code generator has always known about seto. The ppc backend doesn't do the right thing with
it yet.

If this goes in as a legalize change, could a similar change go in for archs
which need to issue an setu | setxx to get unordored comparisons?

That's an interesting approach. Do you suggest a table of supported fp opcodes?

adding nate so he sees recent comments.

Looking into this, we need to be able to refer to subregs of virtual condition registers in order to have
decent codegen.

Consider the two classes of FP comparison we currently get wrong:

1. Unordered + {LT, GT, EQ}.

This should be codegen'd as:
fcmpu crA, fA, fB
cror crA.un, crA.un, crA.{lt,gt,eq}

2. Ordered + {LE, GE}

This should be codegen'd as:
fcmpu crA, fA, fB
cror crA.eq, crA.eq, crA.{lt,gt}

Today, we can only emit cror of physical CR regs, since we have to know the exact bit of the subreg
when we create the node. This works ok for SETCC today, where we force the comparison into CR7
(which would be unnecessary with subreg support). However, for BR_CC or SELET_CC, it currently
forces us to generate incorrect code.

FWIW, we have vreg subregs now, so this should be implementable.

We also get SETONE wrong. I'm working on a hacky patch.

This is (finally!) implemented, Nate, please review:
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080107/056957.html

There's still tons of fixme's in getPredicateForSetCC referencing this bug.

For example:

case ISD::SETOEQ: // FIXME: This is incorrect see llvm/llvm-bugzilla-archive#642 .
case ISD::SETUEQ:
case ISD::SETEQ: return PPC::PRED_EQ;
case ISD::SETONE: // FIXME: This is incorrect see llvm/llvm-bugzilla-archive#642 .
case ISD::SETUNE:

...

This should be fixable now that we have subregs for CR ops

Legalizer can now expand illegal setcc to two setcc anded / ored together. PPC should switch over by adding some setCondCodeAction in PPCISelLowering.cpp. This should fix the bug and eliminate the FIXME's in getPredicateForSetCC.

Dale has agreed to take this. :-)

Shouldn't that be ORd together, not ANDed together?

Ahhh, my reading comprehension isn't so hot today, you said and / or :)

patch
This attached patch seems to work for me in my limited touch testing, but I haven't run full tests with it and won't have time to in the near future. I'd appreciate it if someone could verify that it works and finally close off this old bug.

Sorry, didn't see that you hadn't applied the patch. The patch breaks building llvm-gcc because it rejects SETUGT with integer operands. I'll see if I can fix it.

Assuming SETUGT/SETULT are integer, llvm-gcc builds but the testsuite is worse than before. This needs more work.

OK, I've fixed up Chris' patch a bit and checked it in.
http://llvm.org/viewvc/llvm-project?view=rev&revision=58871
That makes all tests in the gcc testsuite that are obviously about testing FP comparisons pass, at least (and unordered is definitely exercised). So I think this is fixed.

Thanks Dale!