[LLVMdev] Unused malloc/free don't get optimized
Vikram S. Adve
vadve at uiuc.edu
Thu Feb 22 10:41:20 PST 2007
On Feb 22, 2007, at 10:21 AM, Robert L. Bocchino Jr. wrote:
> I glanced at the code again, and it looks like I use DSA to (1)
> construct the call graph and (2) identify things that would be
> unsafe to put on the stack, such as arrays, cyclic data structures,
> and allocations with escaping references. Right now these parts
> are pretty heavily dependent on DSA -- e.g., they make explicit use
> of the various DSA graphs. I'm sure you could modify the code to
> use AliasAnalysis instead of DSA, but I'm not sure what would be
> involved in that.
Unfortunately, I don't think the AliasAnalysis interface gives a way
to check whether allocations escape a function. In DSA, you can do
this because there is an explicit points-to graph: you can find all
objects escaping "upwards" from a function by traversing the graph,
starting at globals, formal arguments, and return values.
--Vikram
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