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[OpenMP][Offloading][2/3] Codegen for target regions (TRegions)
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Authored by jdoerfert on Mar 13 2019, 1:54 PM.

Details

Summary

The commit includes the Clang code generation for OpenMP target
constructs based on the interface target region (TRegion) interface.

The interface was introduced in https://reviews.llvm.org/D59319 .

This target code generation is a vastly simplified clone of the NVPTX
code generation but

  • there is no NVPTX (or other) target specific code, at least there should not be any. The "checkArchForUnifiedAddressing" functionality should therefore be moved to a target specific location later on.
  • we provide hooks for subclasses in order to perform front-end analysis, as an alternative of LLVM based optimizations, e.g., to enable SPMD-mode. (See isKnownSPMDMode, mayNeedRuntimeSupport, and mayPerformDataSharing)

The interface is deliberately simple to be easily analyzable in the
middle end. Design decisions included:

  • Hide all (complex) implementation choices in the runtime library but allow complete removal of the abstraction once the runtime is inlined.
  • Provide all runtime calls with sufficient, easy encoded information.