[PATCH] D129911: [IR] Allow absence for Min module flags and make AArch64 BTI/PAC-RET flags backward compatible

[Fangrui Song via Phabricator via llvm-commits]

MaskRay created this revision.
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D123493 <https://reviews.llvm.org/D123493> introduced llvm::Module::Min to encode module flag metadata for AArch64
BTI/PAC-RET. llvm::Module::Min does not take effect when the flag does not in
one module. This behavior is misleading and does not address backward
compatibility problems (when a bitcode with "branch-target-enforcement"==1 and
another without the flag are merged, the result is 1 instead of 0).

Require Min flags to be non-negative and treat absence as a zero. For an old
bitcode without "branch-target-enforcement"/"sign-return-address", the value is
as if 0.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129911

Files:
  llvm/lib/IR/Verifier.cpp
  llvm/lib/Linker/IRMover.cpp
  llvm/test/Linker/module-flags-min.ll
  llvm/test/Verifier/module-flags-1.ll

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