[LLVMdev] A very basic doubt about LLVM Alias Analysis

ambika ambika at cse.iitb.ac.in
Mon Feb 15 10:34:07 PST 2010


 Using this option I do get all the vars as may alias ie

MayAlias:    i32* %j.0, i32* %k
MayAlias:    i32* %i.0, i32* %k
MayAlias:    i32* %i.0, i32* %j.0

Is there any other analysis which will give them as must aliases.

Actually what I want to do is implement a flow sensitive points-to(not 
alias) analysis and then use that information for some optimizations 
like PRE.
Will that be possible?

> Duncan Sands wrote:
>> Hi Ambika,
>>> to compile it to bitcode I give the following command :
>>>   llvm-gcc -emit-llvm -c -o s.bc s.c
>>> and then I run different alias analysis passes like -anders-aa, 
>>> -basicaa using following:
>>>   opt -anders-aa -aa-eval -print-all-alias-modref-info  s.bc
>> alias analysis will work poorly if you don't run any optimizers.
>> The alias analysis passes assume that at least some basic optimizations
>> have been done.  Try compiling like this:
>>   llvm-gcc -emit-llvm -c -o s.bc s.c -O1
>> Ciao,
>> Duncan.

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