llvm dev - Apr 2009 - [LLVMdev] Assertion `ResultPass && "getAnalysis*() called on an analysis that was not " "'required' by pass!"' failed.

Hello,

I have two passes, A and B.  A is a function pass.  B is a module
pass.  Each uses their getAnalysisUsage() method to .addRequired()
several passes, and each .setPreserveAll()s.  **Pass B requires pass
A**.  But, when I call getAnalysis<A> from within B, it exclaims:

 Assertion `ResultPass && "getAnalysis*() called on an analysis
that
was not " "'required' by pass!"' failed.

Clearly, that is nonsense, because I require that pass.

Under what circumstances can this happen, and why?
-- 
Nick Johnson

I ran into this problem when B would call getAnalysis<A> on an
external function, ie. a declaration rather than a definition in LLVM
terms. If you're iterating over the functions within a module, try
skipping functions for which isDeclaration() returns true. From what I
can gather, the strange error message results from the fact that
function analysis called from modules are generated on the fly, but a
function analysis cannot be performed on an external function so the
analysis is unavailable and the assert triggers believing the pass was
never requested in the first place.


On Thu, Apr 30, 2009 at 2:27 PM, Nick Johnson <npjohnso at
cs.princeton.edu> wrote:
> Hello,
>
> I have two passes, A and B.  A is a function pass.  B is a module
> pass.  Each uses their getAnalysisUsage() method to .addRequired()
> several passes, and each .setPreserveAll()s.  **Pass B requires pass
> A**.  But, when I call getAnalysis<A> from within B, it exclaims:
>
>  Assertion `ResultPass && "getAnalysis*() called on an
analysis that
> was not " "'required' by pass!"' failed.
>
> Clearly, that is nonsense, because I require that pass.
>
> Under what circumstances can this happen, and why?
> --
> Nick Johnson
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