[PATCH] D147016: [PowerPC] Add function pointer alignment to DataLayout

[David Tenty via Phabricator via llvm-commits]

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The alignment of function pointers was added to the Datalayout by
D57335 <https://reviews.llvm.org/D57335> but currently is unset for the Power target. This will cause us
to compute a conservative minimum alignment of one if places like
Value::getPointerAlignment.

This patch implements the function pointer alignment in the Datalayout
for the Power backend and Power targets in clang, so we can query the
value for a particular Power target.

We come up with the correct value one of two ways:

- If the target uses function descriptor objects (i.e. ELFv1 & AIX ABIs), then a function pointer points to the descriptor, so use the alignment we would emit the descriptor with.
- If the target doesn't use function descriptor objects (i.e. ELFv2), a function pointer points to the global entry point, so use the minimum alignment for code on Power (i.e. 4-bytes).


https://reviews.llvm.org/D147016

Files:
  clang/lib/Basic/Targets/OSTargets.h
  clang/lib/Basic/Targets/PPC.h
  clang/test/CodeGen/target-data.c
  llvm/lib/Target/PowerPC/PPCTargetMachine.cpp
  llvm/test/CodeGen/PowerPC/pr45301.ll
  llvm/test/ThinLTO/X86/builtin-nostrip-aix.ll

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