Re: Help with Live Range Analysis?

> There is a pretty decent explanation of how to construct live-in/live-
> out here:http://www.cs.cornell.edu/courses/cs412/2001sp/lectures/lec25.pdf


Small note: unless you need speed, just use the back-tracking
technique in that presentation. Basically, walk backwards over each
basic block. Every time you come to a read of a register that isn't
written-to earlier in the same basic block, look backwards along the
CFG for a write to that register, and add the register to the live-out
sets of any blocks you encounter along the way. The pseudo-code for
the traversal looks like this:


update-live-out(bb, reg):
        set-add(reg, live-out(bb))
        unless set-member?(reg, defed(bb)):
                for pred-bb in preds(bb):
                        update-live-out(pred-bb, reg)


Where the function defed(bb) gives the set of variables written-to by
the instructions in a basic-block, and the function preds(bb) gives
the predecessors of a basic block.

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