Re: [DynInst_API:] getLoopHead interface in BPatch_basicBlockLoop class

[William Hachfeld <wdh@xxxxxxxxxxxxx>]

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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