[LLVMdev] Avoiding Constant Folding

[Cuong Pham]

Thank you guys, now I understand the problem.

I am trying to avoid using stack memory (or mutable variable is the term
used in the tutorial). I am also trying to optimize the code as much as I
can before using optimizer passes such as mem2reg (to reduce the compile
time as well).

With regards,

--Cuong


Duncan Sands wrote:
> 
> Hi,
> 
>>> entry:
>>> ....
>>>   %34 = icmp ne i32 %33, 15
>>>   br i1 %34, label %then, label %else
>>>
>>> then:                                             ; preds = %entry
>>>   %returnValue = or i1 true, false
>>> ....
>>>   br label %ifmerge
>>>
>>> else:                                             ; preds = %entry
>>>   br label %ifmerge
>>>
>>> ifmerge:                                          ; preds = %else, %then
>>> ...
>>>   %41 = icmp ne i32 %40, 15
>>>   br i1 %41, label %then1, label %else3
>>>
>>> then1:                                            ; preds = %ifmerge
>>>   %returnValue2 = or i1 true, %returnValue
> 
> if control flow goes: "entry" -> "else" -> "ifmerge" -> "then1", then you
> will
> try to use %returnValue in then1 without ever defining it.  This is what
> the
> error message is trying to tell you.
> 
> Ciao, Duncan.
> 
>>>
>>> else3:                                            ; preds = %ifmerge
>>>   br label %ifmerge4
>>>
>>> ifmerge4:                                         ; preds = %else3,
>>> %then1
>>> ....
>>>
>>> And I'm getting the following error:
>>> Instruction does not dominate all uses!
>>>   %returnValue = or i1 true, false
>>>   %returnValue2 = or i1 true, %returnValue
>>> Broken module found, compilation aborted!
> 
> Ciao, Duncan.
> _______________________________________________
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> 
> 

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