[all-commits] [llvm/llvm-project] 4c8721: [libc][thumb] support syscalls from thumb mode (#9...

[Nick Desaulniers (paternity leave) via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 4c87212d63c3b45e9371434239553ef007216106
      https://github.com/llvm/llvm-project/commit/4c87212d63c3b45e9371434239553ef007216106
  Author: Nick Desaulniers (paternity leave) <nickdesaulniers at users.noreply.github.com>
  Date:   2024-06-25 (Tue, 25 Jun 2024)

  Changed paths:
    M libc/src/__support/OSUtil/linux/arm/syscall.h

  Log Message:
  -----------
  [libc][thumb] support syscalls from thumb mode (#96558)

r7 is reserved in thumb2 (typically for the frame pointer, as opposed to r11 in
ARM mode), so assigning to a variable with explicit register storage in r7 will
produce an error.

But r7 is where the Linux kernel expects the syscall number to be placed. We
can use a temporary to get the register allocator to pick a temporary, which we
save+restore the previous value of r7 in.

Fixes: #93738



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