[PATCH] D81746: [AArch64] Fix BTI instruction emission.

Mon Jun 15 09:13:37 PDT 2020

nickdesaulniers added inline comments.

================
Comment at: llvm/lib/Target/AArch64/AArch64BranchTargets.cpp:125

-  // PACI[AB]SP are implicitly BTI JC, so no BTI instruction needed there.
-  if (MBBI != MBB.end() && (MBBI->getOpcode() == AArch64::PACIASP ||
-                            MBBI->getOpcode() == AArch64::PACIBSP))
+  // SCTLR_EL1.BT[01] is set to 0 by default which means
+  // PACI[AB]SP are implicitly BTI C so no BTI C instruction is needed there.
----------------
chill wrote:
> chill wrote:
> > What if they are set to a different value?
> Sorry for commenting at this late stage, I didn't know that behavior was configurable.
> Shouldn't there be a test `isTargetAndroid()` and/or `isTargetLinux()` ?
At least for fixing the reported bug in Linux kernels, we shouldn't guard on `isTargetAndroid`; Linux kernels used in Android target aarch64-linux-gnu triples. (Apologies if I misunderstood your question, or if you knew that already).

Re: https://groups.google.com/g/clang-built-linux/c/t2cgw_2fA2w

Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D81746/new/

https://reviews.llvm.org/D81746