[LLVMdev] Fwd: Debugging/Fixing 'Interval not live at use' errors

Tim Northover t.p.northover at gmail.com
Wed Oct 24 05:44:54 PDT 2012

Hi Stephen,

> I'm not entirely sure what is wrong here - I assume it has something to do
> with my 'special' instruction LDri_ab. This instruction is a load with an
> 'address writeback' - ld.ab r0, [r1, 5] is equivalent to ld r0, [r1]; add
> r1, r1, 5. As it was very difficult to match such behaviour automatically, I
> actually only generate them manually for prologue/epilogue emission, so the
> tablegen def is like:

That fits. This line

LDri_ab %FP, %SP, 4

should almost certainly be printed as:

%FP = LDri_ab %SP, 4

The most likely cause is a slightly malformed BuildMI that's adding
%FP without a define flag. Usually you put the destination register
inside the call to BuildMI, and inputs with "addReg(...)" and so on.
All this actually does is fiddle the flags in an appropriate manner;
you can emulate it with addReg, but why bother? So what you should be
looking for is something like:


and changing it to:

BuildMI(LDri_ab, Dest).addReg(Src).addImm(Offset)

Hope this helps.


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