yalla with irregular contig datatype -- Fixes 3566

[alinask]

Yalla has a macro PML_YALLA_INIT_MXM_REQ_DATA that checks if a datatype
is contiguous via opal_datatype_is_contiguous_memory_layout(dt,count)
and if so it selects a size and lb that presumably is what will rdma, as
ompi_datatype_type_size(_dtype, &size);
ompi_datatype_type_lb(_dtype, &lb); \

This failed when I gave it a datatype constructed as [ ...] with extent 4.
What I mean by that datatype is
lens[0] = 3;
disps[0] = 1;
types[0] = MPI_CHAR;
MPI_Type_struct(1, lens, disps, types, &tmpdt);
MPI_Type_create_resized(tmpdt, 0, 4, &mydt);
So there are 3 chars at offset 1, and the LB is 0 and the UB is 4.

So that macro decides that size=4 and lb=0 and later I suppose size is getting
updated to 3 for the final rdma, and so a send of a buffer
[ 0 1 2 3 ] gets recved as [ 0 1 2 _ ]. I think it should use the true lb
and the true extent.

For "regular" contig datatypes it would be the same, and for the irregular
ones that are still deemed contiguous by that utility function it should
still be the right thing to use.

Signed-off-by: Mark Allen [email protected]
(cherry picked from commit 36f51bc)

Fixes #3566

[alinask]

This is a cherry-pick of the fix that @markalle committed to the master branch (#3567).
@jladd-mlnx @yosefe

[bosilca]

We have a special construct that can help with this decision: opal_datatype_span. It returns the span and the initial gap for a block of count datatypes.

[jladd-mlnx]

@hppritcha This is a bug fix, please merge.

[jsquyres]

@alinask GitHub pro tip: you need to put "Fixes #3566" either in the commit message or in the body of the issue description (not the title -- and it must include#) to have this issue both properly refer to #3566 and close #3566 when this PR is merged.

[jsquyres]

@alinask @jladd-mlnx Do we need a PR for this for v2.0.x as well?

[alinask]

@jsquyres Thanks! This was a cherry-pick so I didn't change anything in the commit. Will do for next time.
I issued a PR for v2.x as well - #3766

[jladd-mlnx]

@alinask #3766 is for 3.x. Can you open one for 2.0.x, please.

[jsquyres]

@hppritcha @bwbarrett This seems like an obvious bug fix for v2.0.x-v3.0.x. Good to go.

[jsquyres]

@alinask FWIW/GitHub pro tip: The description of the github PR is pulled from the git commit message (if there's only 1 commit), but you can still change / edit it before the PR is created (and you can edit it after it was created, too).