[PATCH] D36562: [Bitfield] Make the bitfield a separate location if it has width of legal integer type and its bit offset is naturally aligned for the type

[Wei Mi via Phabricator via llvm-commits]

wmi created this revision.
Herald added a subscriber: sanjoy.

Now, all the consecutive bitfields are wrapped as a large integer unless there is unamed zero sized bitfield in between. The patch is trying to make the bitfield to be accessed as separate memory location if it has width of legal integer type and its bit offset is naturally aligned for the type. This can significantly improve the access efficiency of such bitfield.

https://reviews.llvm.org/D30416 wants to achieve the same goal in llvm, but it is much more difficult because it has to deal with the significantly tweaked IR after all sorts of optimizations.

With the patch, we can remove most of https://reviews.llvm.org/D30416 unless the illegal memory access shrinking.


Repository:
  rL LLVM

https://reviews.llvm.org/D36562

Files:
  lib/CodeGen/CGRecordLayoutBuilder.cpp
  test/CodeGen/2009-12-07-BitFieldAlignment.c
  test/CodeGenCXX/2009-12-23-MissingSext.cpp
  test/CodeGenCXX/bitfield.cpp
  test/CodeGenCXX/pod-member-memcpys.cpp
  test/OpenMP/atomic_capture_codegen.cpp
  test/OpenMP/atomic_read_codegen.c
  test/OpenMP/atomic_update_codegen.cpp
  test/OpenMP/atomic_write_codegen.c

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