Tracking issue for demo folder

[ahueck]

The TypeART demo is not properly maintained currently.

Current status

• Makefile broken w.r.t. compiling and deprecated MPI symbols
• CMakeLists untested/out of date?
• Out of date scripts

Issues for release 1.6

• Update Makefile to compile examples with TypeART
• Remove deprecated apply script
• Fix deprecations for OpenMPI 4 or higher

Issues (future)

• Update CMakeLists to build examples
• Add demo to CI system
• Add README.md for demo explanation

[ahueck]

Sections w.r.t. LLVM IR level will be removed from the main README, e.g.,

1.1.3 LLVM compiler pass - Analysis and instrumentation

The analysis pass finds all heap, stack and global allocations. An allocation data-flow filter discards all stack and
global allocations if they are not passed to a target API (default MPI calls). Subsequently, type layouts for
user-defined types (e.g., struct) of these allocations are serialized to a file and a so-called type-id number is
created for each such unique type.

The instrumentation pass adds the instrumentation callbacks to our runtime, passing 1) the memory pointer, 2) the
corresponding type-id and 3) the number of allocated elements (extent).

Example instrumentation in LLVM intermediate representation (IR)

• C and corresponding LLVM IR code: A simple heap allocation with malloc of a double-array. It contains all
  information needed for TypeART:

  double* pointer = (double*) malloc(n * sizeof(double));

  ; Assume: %size == n * sizeof(double)
  %pointer = call i8* @malloc(i64 %size)
  %pointer_double = bitcast i8* %pointer to double*

• Corresponding TypeART instrumentation:

  ; Assume: %size == n * sizeof(double)
  ; Heap allocation -- %pointer holds the returned pointer value:
  %pointer = call i8* @malloc(i64 %size)
  ; TypeART instrumentation -- compute the number of double-elements:
  %extent = udiv i64 %size, 8
  ; TypeART runtime callback (pointer, type-id, length) -- 6 is the type-id for double:
  call void @__typeart_alloc(i8* %pointer, i32 6, i64 %extent)
  ; Original bitcast:
  %pointer_double = bitcast i8* %pointer to double*