Oct 20 2021 meeting notes

Oct 20 2021 meeting notes

[Nick Desaulniers]

- Lots of patches around `-Wbitwise-instead-of-logical`, Linus not
thrilled with note diagnostic.
- (Nick) [eliminated](https://lore.kernel.org/lkml/20211019223646.1146945-2-ndesaulniers@google.com/)
CROSS_COMPILE_COMPAT for LLVM=1 arm64 compat vdso.
- (Serge) [fix](https://reviews.llvm.org/D112059) for
[LTO+FORTIFY](https://github.com/ClangBuiltLinux/linux/issues/1477).
- arm64 `.cfi_negate_ra_state`+PAC [LLVM
patch](https://reviews.llvm.org/D111780).
- (Nick) thinLTO+CFI .cfi_jt fixup [LLVM
patch](https://reviews.llvm.org/D107934).
- (Ard) arm32 [IRQ
stacks](https://lore.kernel.org/linux-arm-kernel/20211017131723.4034662-1-ardb@kernel.org/)
and [vmapped stacks](https://lore.kernel.org/linux-arm-kernel/20211018141615.682070-1-ardb@kernel.org/).
  - regression in next `__eabi_read_tb`
- (Nick) working on [propagating tail
calls](https://reviews.llvm.org/D107872) for fortify.
- 32b [unwinder
fixes](https://lore.kernel.org/linux-arm-kernel/163369614818.636038.5019945597127474028.stgit@devnote2/)
for kprobes.
- (Miguel) [mark](https://lore.kernel.org/lkml/20211014132331.GA4811@kernel.org/)
`__compiletime_assert` `noreturn`.
- [MPE](https://lore.kernel.org/linuxppc-dev/20211014024424.528848-1-mpe@ellerman.id.au/)
and Nemanjai looking into LLVM_IAS=1 for ppc.
- (Rasmus) [switch container_of from BUILD_BUG_ON to
static_assert](https://lore.kernel.org/lkml/20211015090530.2774079-1-linux@rasmusvillemoes.dk/).
- kasan excessive stack useage, [interesting
case](https://godbolt.org/z/P3qb4nGYe) fron Arnd.
  - `-fno-sanitize-address-use-after-scope` and
`-fsanitize-address-use-after-return=never` (gcc's `--param
asan-use-after-return=1`)
  - large padding for small locals?
- LLVM bay area meetup tonight. 5pm CBL round table.
  - ppc & s390 assembler, kasan stack useage, ARC + m68k
- atom cpu tuning is bad; leads to frequent register exhaustion.
(TODO: Nick, talk to Intel):
https://github.com/ClangBuiltLinux/linux/issues/1483
- rust tentative clang flags removed from rustforlinux kbuild modifications
- https://github.com/ClangBuiltLinux/linux/issues/1315: argument
unused during compilation: '-march=armv6k' #1315

-- 
Thanks,
~Nick Desaulniers