Regent: potential bug in inliner

[mariodirenzo]

The following script

import 'regent'

local C = regentlib.c
local HDF5 = terralib.includec('hdf5.h')

HDF5.H5F_ACC_RDONLY = 0
HDF5.H5P_DEFAULT = 0

-- The script compiles if this task is not inlined or if the call to
-- H5Aread is commented out
__demand(__inline)
task readIspaceFromHDF5(dirname : regentlib.string)
   -- Open file
   var filename = [&int8](C.malloc(256))
   C.snprintf(filename, 256, '%s/master.hdf', [&int8](dirname))
   var fid = HDF5.H5Fopen(filename, HDF5.H5F_ACC_RDONLY,
                          HDF5.H5P_DEFAULT)
   -- Register data types to describe index spaces
   var colorType = HDF5.H5Tcreate(HDF5.H5T_COMPOUND, 24)
   var x = HDF5.H5Tinsert(colorType, "x",  0, HDF5.H5T_STD_I64LE_g)
   var y = HDF5.H5Tinsert(colorType, "y",  8, HDF5.H5T_STD_I64LE_g)
   var z = HDF5.H5Tinsert(colorType, "z", 16, HDF5.H5T_STD_I64LE_g)
   -- Check number of tiles
   var res = HDF5.H5Aexists_by_name(fid, ".", "tilesNumber",
                                    HDF5.H5P_DEFAULT)
   var aid = HDF5.H5Aopen(fid, "tilesNumber", HDF5.H5P_DEFAULT)
   var out : int64[3]
   res = HDF5.H5Aread(aid, colorType, &out)
   -- Clean up
   HDF5.H5Aclose(aid)
   HDF5.H5Tclose(colorType)
   HDF5.H5Fclose(fid)
   C.free(filename)
   return int3d{out[0], out[1], out[2]}
end

task main()
   var dirname = "."
   var dim3 = readIspaceFromHDF5(dirname)
end

regentlib.saveobj(main, "test.o")

fails with the error

/Users/direnzo/Codes/legion/language/src/common/ast.t:520: wrong number of arguments to 'insert'
stack traceback:
    [C]: in function 'insert'
    /Users/direnzo/Codes/legion/language/src/common/ast.t:520: in function 'map_node_postorder'
    /Users/direnzo/Codes/legion/language/src/common/ast.t:511: in function 'expr'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:348: in function <.../direnzo/Codes/legion/language/src/regent/inline_tasks.t:346>
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:371: in function 'stat'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:375: in function 'fn'
    ...rs/direnzo/Codes/legion/language/terra/src/terralist.lua:150: in function 'map'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:375: in function 'block'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:441: in function 'expr_call'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:518: in function 'expr'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:538: in function <.../direnzo/Codes/legion/language/src/regent/inline_tasks.t:534>
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:588: in function 'stat'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:593: in function 'fn'
    ...rs/direnzo/Codes/legion/language/terra/src/terralist.lua:150: in function 'map'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:593: in function 'block'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:598: in function 'top_task'
    .../direnzo/Codes/legion/language/src/regent/inline_tasks.t:608: in function <.../direnzo/Codes/legion/language/src/regent/inline_tasks.t:602>
    /Users/direnzo/Codes/legion/language/src/regent/passes.t:64: in function </Users/direnzo/Codes/legion/language/src/regent/passes.t:57>
    RegentInlinerBug.rg:39: in main chunk

if executed with the command INCLUDE_PATH=$HDF_ROOT/include $LEGION_DIR/language/regent.py RegentInlinerBug.rg. If the task readIspaceFromHDF5 is not inlined or if the call to H5Aread is commented out, the script is executed correctly.

[elliottslaughter]

@mariodirenzo What machine are you hitting this on?

@magnatelee has a workaround, but it seems to be a LuaJIT bug.

[magnatelee]

or a Terra bug, if Terra was messing with tokens from the lexer.

I pushed this workaround to master and control replication: https://gitlab.com/StanfordLegion/legion/-/commit/07a5d195e6d644f772fba6da4e443969d9479107. Let me know if this still doesn't fix your issue.

[elliottslaughter]

Here's a new reproducer. This is the shortest one I've been able to make, and (fortunately) does not require HDF5.

import 'regent'

terra f(x : &int64)
  return 123
end

__demand(__inline)
task g()
   var out : int64
   var res = f(&out)
end

task main()
   g()
end
main:compile()

[elliottslaughter]

I'm suspecting Wonchan may be right about the Terra parser, but just for posterity: I reproduced on Moonjit and two versions of LuaJIT (most recent v2.1, and a version about 2 years old that's currently checked in to Terra).

[mariodirenzo]

What machine are you hitting this on?

I discovered it on my mac with Moonjit.

Let me know if this still doesn't fix your issue.

The problem seems solved. Thanks!

Should we leave this issue open until you find out if this is a LuaJIT or Terra bug?

[elliottslaughter]

It's looking like this is a Terra issue, but I'm not sure how to move forward with debugging because—even with the minimal reproducer program—we're effectively debugging the Terra parser against the entire Regent compiler code base. Even if I add diagnostics to Terra to show the parser state, there will be far too much to look through if I run it past the entire compiler.

Anyway, let's leave this open for now. I'll deprioritize it in #1189.