[LLVMdev] def-use chains and use-def chains

[Duncan Sands]

Hi Srikanth Vaindam,

> I frankly don't know what a variable gets converted to (SSA register or memory
> chunk).

this is pretty important, so you would do well to know.

  What I meant is, for example
>
> I1: int i, j=10; I2: scanf("%d", &j); I3: i = j + 1;
>
> Here I want to know whether the value of j in I1 reaches I3 or not.

In this case you are talking about a chunk of memory.  Probably you are looking
for something like memdep (MemoryDependenceAnalysis.cpp).

Ciao, Duncan.

>
>
> Best Regards,
> Srikanth Vaindam
>
>
> you didn't define what you mean by a variable.  LLVM has virtual registers which
> are always in SSA form, and memory (such as created by an AllocaInst).  By a
> "variable" do you mean an SSA register, or do you mean a chunk of memory?
>
> Ciao, Duncan.
>
>
> On Thu, Apr 19, 2012 at 11:35 AM, srikanth vaindam <srikanth.vaindam at gmail.com
> <mailto:srikanth.vaindam at gmail.com>> wrote:
>
>     Hi,
>     I need to find out all the places where the value of a variable is being
>     used. For this I have to implement reaching definitions(def-use chains).
>     When I searched for its implementation I found Iterating over def-use &
>     use-def chains <http://llvm.org/docs/ProgrammersManual.html#iterate_chains>.
>     will this work for finding the places where a variable is reaching?
>
>     I tried to use "use_iterator", but couldn't make it out. Is it a must to
>     write LLVM Pass to use op_iterator and use_iterator?
>     please give me any references or examples to understand more about use_iterator.
>
>
>     Best Regards,
>     Srikanth Vaindam
>
>
>
>
>
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