search for: heapifi

Hi all, I have been writing a pass to heapify some alloca's (it is pessimistization, not optimization). For example, in the following control flow graph, there is a call to malloc inserted in block BB12. In order to avoid memory leak, free's are needed. The free cannot be inserted in BB23 because BB23 is not dominated by BB12. There are two ways to go I can think of here. One way is to

Hi Henrique, Thanks for the quick reply! On Tue, Nov 12, 2013 at 9:13 PM, Henrique Santos < henrique.nazare.santos at gmail.com> wrote: > PRE normally uses a latest placement algorithm to do something of the sort. > I don't know about GVN/PRE, but older version of PRE might have it. > Just placing the calls to free at the predecessors (dominated by BB12) of > the dominance

PRE normally uses a latest placement algorithm to do something of the sort. I don't know about GVN/PRE, but older version of PRE might have it. Just placing the calls to free at the predecessors (dominated by BB12) of the dominance frontier of BB12 seems to work, however. Is there anything wrong with this? H. On Tue, Nov 12, 2013 at 11:30 PM, Bin Tzeng <bintzeng at gmail.com> wrote:

> > It seems that placing the calls to free at the predecessors of dominance > frontier is inadequate. It is possible that there are exit blocks that are > dominated by BB12 (calls to malloc). I guess we can also insert calls to > free at these exit blocks too. That crossed my mind a few minutes later. : ) If you're interested, PRE.cpp existed last at r25315. It calculates the

Thanks! I will try that and see whether it works. On Wed, Nov 13, 2013 at 5:01 AM, Henrique Santos < henrique.nazare.santos at gmail.com> wrote: > It seems that placing the calls to free at the predecessors of dominance >> frontier is inadequate. It is possible that there are exit blocks that are >> dominated by BB12 (calls to malloc). I guess we can also insert calls to

Bill, Just in case this is relevant for you: If you're working with C++ code, or otherwise have any functions that might throw exceptions, you might also need to catch those exceptions in order to free the allocated memory. This will involve looking for calls to functions that mayThrow(), changing their calls to invokes, and freeing the memory before resuming the unwinding. -Hal -----

Hi Henrique, I have tried using -mergereturn and inserting a free into the predecessors of dominance frontier of malloc block and it caused double free. It is possible for multiple free's to be inserted on the path from malloc to an exit. For example, in the following CFG: BB10 (malloc) / \ BB11 BB12 ... / \ / \

Try breaking the critical edges (-break-crit-edges). This way, a new block will be created between BB13 and BB11 (call this BB11.break) and BB15 and BB12 (call this BB12.break). The predecessors of the dominance frontier will, thus, be BB11.break, BB12.break, and BB14. When we enter through a block with a call to malloc(), we will end up in one of the blocks in the dominance frontier (kind of).