llvm dev - Feb 2005 - [LLVMdev] Uniform data dependence info?

Guys,

Is there some uniform way to find data dependence between
two (sets of) instructions?  There is use/def data, and
there is AliasAnalysis information, but I am looking for
something more high-level and uniform.  I guess I am missing
something, because such interface seems to exist once and
then was abandoned. Any ideas?

    Victor
--
  IBM Research Lab in Haifa, Israel

> Is there some uniform way to find data dependence between two (sets of) 
> instructions?  There is use/def data, and there is AliasAnalysis 
> information, but I am looking for something more high-level and uniform. 
> I guess I am missing then was abandoned. Any ideas?
Nope, there currently isn't a uniform interface for doing so, at least not 
at the LLVM level.  As you said, use/def information will tell you about 
dependence between non-side-effecting instructions, and AliasAnalysis will 
tell you what dependences exist between side-effecting ones.

What are you trying to do here?  It would be really easy to add a helper 
method to the AliasAnalysis interface that took into consideration 
dependencies between scalar instructions.  What specific information do 
you need?

-Chris

-- 
http://nondot.org/sabre/
http://llvm.cs.uiuc.edu/

> What specific information do you need?
All my experiments eventually analyze or transform
the data dependence graph, which takes into account both
registers and aliasing information.  Because there is already
a built-in support for graphs, I hoped there is also built-in
support for data dependence graphs. That would allow, for example,
to display them naturally with dot utility.

      Victor



                      Chris Lattner
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                      >                        cc:       Victor
Leikehman/Haifa/IBM at IBMIL
                      Sent by:                 Subject:  Re: [LLVMdev] Uniform
data dependence info?
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                      02/23/05 06:02 PM
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> Is there some uniform way to find data dependence between two (sets of)
> instructions?  There is use/def data, and there is AliasAnalysis
> information, but I am looking for something more high-level and uniform.
> I guess I am missing then was abandoned. Any ideas?
Nope, there currently isn't a uniform interface for doing so, at least not
at the LLVM level.  As you said, use/def information will tell you about
dependence between non-side-effecting instructions, and AliasAnalysis will
tell you what dependences exist between side-effecting ones.

What are you trying to do here?  It would be really easy to add a helper
method to the AliasAnalysis interface that took into consideration
dependencies between scalar instructions.  What specific information do
you need?

-Chris

--
http://nondot.org/sabre/
http://llvm.cs.uiuc.edu/

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