feat(rocSHMEM): separate p and g from memcpy paths, #AIROCSHMEM-506

[amirsojoodi]

Motivation

Enable IPC backend to move to global instructions from flat ones.

Technical Details

• Add memcpy_lane_scalar<Kind>(dst, src, size) to util.hpp, mirroring memcpy_lane's signature, to back scalar p()/g() RMA
• Add putmem_scalar/getmem_scalar to IPCContext and GDAContext, mirroring the existing putmem/getmem pattern, and rewire p()/g() to use them
• Revert the Access asm blocks from flat instructions to global

Issue Tracking

JIRA ID: AIROCSHMEM-506

[therock-pr-bot]

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Check	Status	Details
📝 PR Description	✅ Pass	—
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🧪 Unit Test	⚠️ Warning	Error: Source/code files changed without an accompanying unit test. Expected: add at least one test file named like test_<name>.py / test_<name>.cpp (or <name>_test.*). Current: code file(s) changed: projects/rocshmem/src/assembly.hpp, projects/rocshmem/src/gda/context_gda_device.cpp, projects/rocshmem/src/gda/context_gda_device.hpp, projects/rocshmem/src/gda/context_gda_tmpl_device.hpp, projects/rocshmem/src/ipc/context_ipc_device.cpp (+3 more); no test file found
🚫 Draft PR	🔜 To Be Enabled	—
🚩 Feature Flag	🔜 To Be Enabled	—
📊 Code Coverage	🔜 To Be Enabled	—

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[Copilot]

Pull request overview

This PR introduces a scalar-specific RMA fast path for p()/g() so IPC/GDA backends can safely use global (non-flat) load/store instructions without accidentally applying them to non-global (e.g., private/stack) addresses.

Changes:

• Add memcpy_lane_scalar<Kind>(dst, src, size) for byte-size-dispatched scalar copies that only apply AsmAccess to the remote pointer.
• Add putmem_scalar/getmem_scalar to IPC and GDA contexts and rewire p()/g() to use these scalar paths.
• Switch AsmAccess inline asm from flat_* to global_* instructions and document the “global address required” constraint.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
projects/rocshmem/src/util.hpp	Adds scalar lane copy helper and documents global-address constraints for bulk/remainder paths.
projects/rocshmem/src/ipc/context_ipc_tmpl_device.hpp	Rewires IPC p()/g() to use scalar put/get helpers.
projects/rocshmem/src/ipc/context_ipc_device.hpp	Declares IPC putmem_scalar/getmem_scalar.
projects/rocshmem/src/ipc/context_ipc_device.cpp	Implements IPC scalar put/get via memcpy_lane_scalar.
projects/rocshmem/src/gda/context_gda_tmpl_device.hpp	Rewires GDA p()/g() to use scalar put/get helpers.
projects/rocshmem/src/gda/context_gda_device.hpp	Declares GDA putmem_scalar/getmem_scalar.
projects/rocshmem/src/gda/context_gda_device.cpp	Implements GDA scalar put/get (IPC fast-path + fallback behavior).
projects/rocshmem/src/assembly.hpp	Updates AsmAccess to emit global_load_* / global_store_* asm and updates related commentary.

Suppressed comments (4)

projects/rocshmem/src/util.hpp:516

• Same strict-aliasing/alignment issue as the 1-byte case: dereferencing Acc::type* from a T*-backed pointer is UB when T differs in signedness or alignment. Prefer memcpy to/from a temporary.

    if constexpr (is_put(Kind)) {
      Acc::store(dst, *static_cast<typename Acc::type*>(src));
    } else {
      *static_cast<typename Acc::type*>(dst) = Acc::load(src);
    }

projects/rocshmem/src/util.hpp:525

• Same strict-aliasing/alignment issue as above: avoid dereferencing Acc::type* sourced from a void* that actually points to a T object by using memcpy to/from a temporary.

    if constexpr (is_put(Kind)) {
      Acc::store(dst, *static_cast<typename Acc::type*>(src));
    } else {
      *static_cast<typename Acc::type*>(dst) = Acc::load(src);
    }

projects/rocshmem/src/util.hpp:534

• Same strict-aliasing/alignment issue as above for the 8-byte case. Using memcpy avoids UB when p()/g() instantiate for unsigned 64-bit types or types with weaker alignment.

    if constexpr (is_put(Kind)) {
      Acc::store(dst, *static_cast<typename Acc::type*>(src));
    } else {
      *static_cast<typename Acc::type*>(dst) = Acc::load(src);
    }

projects/rocshmem/src/util.hpp:543

• Same strict-aliasing/alignment issue as above for the 16-byte case: dereferencing Acc::type* is UB if the pointed-to object isn't actually __int128_t (or isn't sufficiently aligned). memcpy to/from a temporary avoids that.

    if constexpr (is_put(Kind)) {
      Acc::store(dst, *static_cast<typename Acc::type*>(src));
    } else {
      *static_cast<typename Acc::type*>(dst) = Acc::load(src);
    }

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