[PATCH] D77048: [Clang][CodeGen] Fixing mismatch between memory layout and const expressions for oversized bitfields

[Lucas Prates via Phabricator via cfe-commits]

pratlucas created this revision.
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The construction of constants for structs/unions was conflicting the
expected memory layout for over-sized bit-fields. When building the
necessary bits for those fields, clang was ignoring the size information
computed for the struct/union memory layout and using the original data
from the AST's FieldDecl information. This caused an issue in big-endian
targets, where the field's contant was incorrectly misplaced due to
endian calculations.

This patch aims to separate the constant value from the necessary
padding bits, using the proper size information for each one of them.
With this, the layout of constants for over-sized bit-fields matches the
ABI requirements.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D77048

Files:
  clang/lib/CodeGen/CGExprConstant.cpp
  clang/test/CodeGenCXX/bitfield-layout.cpp

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