[PATCH] D111343: [x86] Implement a tagged-globals backend feature.

[Matt Morehouse via Phabricator via llvm-commits]

morehouse created this revision.
morehouse added reviewers: pcc, eugenis, hctim, vitalybuka.
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The feature tells the backend to allow tags in the upper bits of global
variable addresses.  These tags will be ignored by upcoming CPUs with
the Intel LAM feature but may be used in instrumentation passes (e.g.,
HWASan).

This patch implements the feature by using @GOTPCREL relocations instead
of direct references to the locally defined global.  Thus the full
tagged address can be loaded by a single instruction:

  movq global at GOTPCREL(%rip), %rax


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D111343

Files:
  llvm/lib/Target/X86/X86.td
  llvm/lib/Target/X86/X86Subtarget.cpp
  llvm/lib/Target/X86/X86Subtarget.h
  llvm/test/CodeGen/X86/tagged-globals-pic.ll
  llvm/test/CodeGen/X86/tagged-globals-static.ll

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