Re: [DynInst_API:] getLoopHead interface in BPatch_basicBlockLoop class

[Xiaozhu Meng <xmeng@xxxxxxxxxxx>]

Hi Bill,

I am not clear about the concept of the "defining statement of the
loop". If the "defining statement of the loop" refers to the statement
in the loop that has the minimum source line number, then I think your
alternative way can work. But if the "defining statement of the loop"
refers to the statement that contains the loop condition, then your
alternative way would not work because the loop condition can be last
source statement of the loop. Could you provide more details on what
you mean by the defining statement of the loop?

Thanks

--Xiaozhu

On Thu, Jul 30, 2015 at 9:28 PM, William Hachfeld <wdh@xxxxxxxxxxxxx> wrote:
>
> Hi Jim,
>
> To get a better understanding of what Xiaozhu is writing about, take a look
> at the diagrams on the right side of:
>
> https://en.wikipedia.org/wiki/Control_flow_graph
>
> Figure (d) shows an irreducible CFG. In particular, Xiaozhu is indicating
> that the new API is designed to allow for the representation of the two
> middle nodes in (d). These two nodes represent a loop which has 2 different
> entry points. I.e. multiple âheadâ.
>
> Unfortunately because the old Dyninst API didnât handle this case, the
> Open|SpeedShop database schema I designed doesnât either. :-( It also
> doesnât necessarily matter. The only place that the âaddr_headâ value is
> used is in order to identify which source statement is the âdefinitionâ of
> the loop.
>
> Is there some, alternate, way of identifying which basic block is contained
> within the defining statement of the loop, Xiaozhu? I donât have the Dyninst
> 9 API available to me right nowâ Otherwise we need some alternate mechanism
> of picking the âheadâ address, Jim.
>
> One possibility - just off the cuff mind you - might be to call
> getLoopEntries() to get the basic block of each entry. Then, for each of
> these, take the first address of that basic block and query the source
> file/line containing that address. Assuming that all line numbers are within
> a single source file, the minimum line number is probably reasonably the
> loop definition. And the first address in that basic block would be the one
> to use for âaddr_headâ in the Open|SS database.
>
> â Bill
>
>
>
> On Jul 28, 2015, at 11:08 AM, Xiaozhu Meng <xmeng@xxxxxxxxxxx> wrote:
>
> It is more complicated than that. For a natural loop, it only has one
> entry, which is also called the head because the entry dominates all
> blocks of the loop. However, for an irreducible loop, it can have
> multiple entries and it is possible that none of the entries dominates
> the other blocks in the loop.
>
> Thanks
>
> --Xiaozhu
>
> On Tue, Jul 28, 2015 at 10:58 AM, Jim Galarowicz <jeg@xxxxxxxxxxxxx> wrote:
>
> Hi Xiaozhu,
>
> Is the first entry in the vector e the loop head?
>
>
>                BPatch_Vector<BPatch_basicBlock*> entries;
>                loop->getLoopEntries(entries);
>                BPatch_basicBlock* head = entries[0];
>
>                if (head == NULL)
>                {
>                    continue;
>                }
>
>                LoopInfo info(Address(head->getStartAddress()) -
> module_base);
>
>                BPatch_Vector<BPatch_basicBlock*> blocks;
>                loop->getLoopBasicBlocks(blocks);
>
>                for (unsigned int i = 0; i < blocks.size(); ++i)
>                {
>                    BPatch_basicBlock* block = blocks[i];
>
>
> Or is it more complicated than that?
>
> Thanks,
> Jim G
>
>
> Thanks,
> Jim G
> On 07/28/2015 10:37 AM, Xiaozhu Meng wrote:
>
>
> Hi Jim,
>
> The old getLoopHead() method has been replaced by the following new
> interface to appropriately represent irreducible loops:
>
> int
> BPatch_basicBlockLoop::getLoopEntries(BPatch_Vector<BPatch_basicBlock*> &e);
>
> The new interface returns the number of entry blocks of this loop and
> the entries blocks are returned as the output parameter.
>
> On Tue, Jul 28, 2015 at 8:42 AM, Jim Galarowicz <jeg@xxxxxxxxxxxxx> wrote:
>
>
> Hi all,
>
> I've downloaded the git source version of dyninst and built it on NASA's
> pfe
> machine and my laptop in an attempt to run it on Intel MIC binaries.  The
> 8.2.1 asserts in switches related to the architecture type.
>
> However, I ran into a compile error with our loop code:
>
> [ 16%] Building CXX object
>
> libopenss-framework/CMakeFiles/openss-framework-symtabapi.dir/DyninstSymbols.cxx.o
> cd /u/jgalarow/OpenSpeedShop/build_mic_offline_fe/libopenss-framework &&
> /nasa/pkgsrc/2014Q3/gcc49/bin/g++   -DHAVE_DYNINST -DHAVE_STDINT_H=1
> -DHAVE_SYS_STAT_H=1 -DOPENSS_USE_SYMTABAPI=1
>
> -DOpenSpeedShop_LIBRARY_FILE_DIR=\"/nobackupp8/jgalarow/maia/pfe_ossoffline/lib64\"
> -DPACKAGE=1 -DPACKAGE_VERSION=1 -DVERSION=\"2.1\" -D_GNU_SOURCE
> -Dopenss_framework_symtabapi_EXPORTS -g -fPIC
> -I/u/jgalarow/OpenSpeedShop/libopenss-framework
> -I/u/jgalarow/OpenSpeedShop/build_mic_offline_fe/libopenss-framework
>
> -I/u/jgalarow/OpenSpeedShop/build_mic_offline_fe/libopenss-framework/offline
> -I/nasa/boost/1.50.0/include
> -I/nobackup/jgalarow/dyninst-9.0.0/include/dyninst
> -I/nobackup/jgalarow/dyninst-9.0.0/include
> -I/u/jgalarow/krellroot_v2.1u8/include
>
> -I/u/jgalarow/OpenSpeedShop/build_mic_offline_fe/libopenss-framework/../libopenss-framework
> -o CMakeFiles/openss-framework-symtabapi.dir/DyninstSymbols.cxx.o -c
> /u/jgalarow/OpenSpeedShop/libopenss-framework/DyninstSymbols.cxx
> /u/jgalarow/OpenSpeedShop/libopenss-framework/DyninstSymbols.cxx: In
> function 'std::vector<LoopInfo> getLoopsAt(const
> OpenSpeedShop::Framework::Address&, BPatch_image&)':
> /u/jgalarow/OpenSpeedShop/libopenss-framework/DyninstSymbols.cxx:140:49:
> error: 'class BPatch_basicBlockLoop' has no member named 'getLoopHead'
>                  BPatch_basicBlock* head = loop->getLoopHead();
>                                                  ^
> make[2]: ***
>
> [libopenss-framework/CMakeFiles/openss-framework-symtabapi.dir/DyninstSymbols.cxx.o]
> Error 1
> make[2]: Leaving directory
> `/home4/jgalarow/OpenSpeedShop/build_mic_offline_fe'
> make[1]: ***
> [libopenss-framework/CMakeFiles/openss-framework-symtabapi.dir/all] Error
> 2
> make[1]: Leaving directory
> `/home4/jgalarow/OpenSpeedShop/build_mic_offline_fe'
>
> I found this in my emails about dyninst:
>
> Hi,
>
> We are planing to improve our current loop detection algorithm to be able
> to
> handle irreducible loops. Such loops can have multiple entry blocks. For
> this matter, the original interface to get the loop head needs to be
> changed
> to return a vector of heads of a loop.
>
> The involved interface is:
>
> BPatch_basicBlock*  BPatch_basicBlockLoop::getLoopHead();
>
> We plan to change it to:
>
> bool BPatch_basicBlockLoop::getLoopHead(std::vector<BPatch_basicBlock*>&
> entries);
>
> Let us know if you are using the interface and if the interface change
> will
> cause significant inconvenience to you.
>
> Thanks
>
> --Xiaozhu
>
>
> However, I can't find any examples of the new getLoopHead code in the
> latest
> Dyninst source.   Can someone point me to it?
>
>
> pfe21-101>pwd
> /nobackupp8/jgalarow/OpenSpeedShop_ROOT/BUILD/pfe20/dyninst-9.0.0
>
> pfe21-94>grep basicBlockLoop::getLoopHead *
> pfe21-95>!!/*
> grep basicBlockLoop::getLoopHead */*
> pfe21-96>!!/*
> grep basicBlockLoop::getLoopHead */*/*
> pfe21-97>!!/*
> grep basicBlockLoop::getLoopHead */*/*/*
> pfe21-98>!!/*
> grep basicBlockLoop::getLoopHead */*/*/*/*
> pfe21-99>!!/*
> grep basicBlockLoop::getLoopHead */*/*/*/*/*
> pfe21-100>!!/*
> grep basicBlockLoop::getLoopHead */*/*/*/*/*/*
> pfe21-101>pwd
> /nobackupp8/jgalarow/OpenSpeedShop_ROOT/BUILD/pfe20/dyninst-9.0.0
>
> pfe21-104>grep getLoopHead *
> pfe21-105>!!/*
> grep getLoopHead */*
> pfe21-106>!!/*
> grep getLoopHead */*/*
> !!/*
>
> LOOKS LIKE THE OLD INTERFACE:
>
> dyninstAPI/src/hybridOverwrites.C://
> (*lIter)->getLoopHead()->getStartAddress(),
> dyninstAPI/src/hybridOverwrites.C://
> writeLoop->getLoopHead()->getStartAddress(),
> pfe21-107>!!/*
> grep getLoopHead */*/*/*
> pfe21-108>!!/*
> grep getLoopHead */*/*/*/*
> pfe21-109>!!/*
> grep getLoopHead */*/*/*/*/*
> pfe21-110>
>
>
> I need to change this to work with the new API:
> cat -n /u/jgalarow/OpenSpeedShop/libopenss-framework/DyninstSymbols.cxx
> ...
> ...
>
>   122                BPatch_Vector<BPatch_basicBlockLoop*> loops;
>    123                cfg->getLoops(loops);
>    124
>    125                for (unsigned int l = 0; l < loops.size(); ++l)
>    126                {
>    127                    BPatch_basicBlockLoop* loop = loops[l];
>    128
>    129                    if ((loop == NULL) ||
> !loop->containsAddressInclusive(
>    130                            (module_base + address).getValue()
>    131                            ))
>    132                    {
>    133                        continue;
>    134                    }
>    135
>    136                    // A loop containing this address has been
> found!
> Rejoice!
>    137                    // And, of course, obtain the loop's head
> address
> and basic
>    138                    // block address ranges...
>    139
>    140                    BPatch_basicBlock* head = loop->getLoopHead();
>    141
>    142                    if (head == NULL)
>    143                    {
>    144                        continue;
>    145                    }
>    146
>    147                    LoopInfo info(Address(head->getStartAddress())
> -
> module_base);
>    148
>    149                    BPatch_Vector<BPatch_basicBlock*> blocks;
>    150                    loop->getLoopBasicBlocks(blocks);
>    151
>    152                    for (unsigned int i = 0; i < blocks.size();
> ++i)
>    153                    {
> ...
> ...
>
>
> Thanks,
> Jim G
>
>
> On 09/23/2014 04:57 PM, Xiaozhu Meng wrote:
>
> Hi,
>
> We are planing to improve our current loop detection algorithm to be able
> to
> handle irreducible loops. Such loops can have multiple entry blocks. For
> this matter, the original interface to get the loop head needs to be
> changed
> to return a vector of heads of a loop.
>
> The involved interface is:
>
> BPatch_basicBlock*  BPatch_basicBlockLoop::getLoopHead();
>
> We plan to change it to:
>
> bool BPatch_basicBlockLoop::getLoopHead(std::vector<BPatch_basicBlock*>&
> entries);
>
> Let us know if you are using the interface and if the interface change
> will
> cause significant inconvenience to you.
>
> Thanks
>
> --Xiaozhu
>
>
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>
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