[LLVMdev] Problems expanding fcmp to a libcall

[Richard Osborne]

I'm trying to write a backend for a target with no hardware floating
point support. I've added a single i32 register class. I'm wanting all
floating point operations to be lowered to library function calls. For
the most part LLVM seems to get this right. For example

define double @div(double %a, double %b) {
 %result = fdiv double %a, %b
 ret double %result
}

is expanded to a ISD::CALL of __divdf3 which is then lowered via the
LowerOperation hook of my backend.

However I run into problems with fcmp. With the following code:

define i1 @fmp(double %a) {
 %result = fcmp uno double %a, 0.000000e+00
 ret i1 %result
}

the fcmp is expanded to the a call to __unorddf2 which is then
lowered via the LowerOperation hook of my backend. However for some reason
there remains a ISD::CALL node with __unorddf2 in the DAG after
legalization. This
then causes selection to fail with

Cannot yet select: 0x13b7cc0: i32,i32,ch = call 0x13b76e0, 0x13b7800,
0x13b7800, 0x13b7800, 0x13b77a0, 0x13b78f0, 0x13b79a0, 0x13b80d0,
0x13b7a00, 0x13b78f0, 0x13b79a0, 0x13b80d0, 0x13b7a00

Are there any additional steps I need to take in my target, or could
this be a bug in the Legalization phase?

Regards,

Richard Osborne