[LLVMdev] indirectbr and phi instructions

[Joshua Warner]

Hi,

How does the requirement that phi instructions have one value per
predecessor basic block interact with indirectbr instructions?  For
instance, take the following code:

L1:
   br i1 %somevalue, label %L2, label %L3
L2:
   %ret1 = i8* blockaddress(@myfunction, %L5)
   br label %L4
L3:
   %ret2 = i8* blockaddress(@myfunction, %L6)
   br label %L4
L4:
   %ret = phi i8* [%ret1, L2], [%ret2, L3]
   indirectbr i8* %ret, [label %L5, label %L6]
L5:
   %myval = phi i32 [0, %L2], [1, %L3] ; are both of these values required,
even though the only *real* possible predecessor block is L2?
   ret i32 %myval
L6:
   %myval = phi i32 [0, %L2], [1, %L3] ; likewise
   ret i32 %myval

Boiled down, I think my question is, "how strict is the 'one value per
predecessor block' rule on a phi instruction?"

FYI, I am planning on using indirectbr to implement jsr and ret instructions
in Java.  I fully expect that there are syntax errors in the above code -
but I hope you get the idea.

Thanks,

Joshua
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