clang: work around asm input constraint problems
Work around clang problems with asm constraints that have multiple
possibilities, particularly "g" and "rm".
Clang seems to turn inputs like that into the most generic form, which
is the memory input - but to make matters worse, clang won't even use a
possible original memory location, but will spill the value to stack,
and use the stack for the asm input.
See
https://github.com/llvm/llvm-project/issues/20571#issuecomment-980933442
for some explanation of why clang has this strange behavior, but the end
result is that "g" and "rm" really end up generating horrid code.
Link: https://github.com/llvm/llvm-project/issues/20571
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: H. Peter Anvin <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2 files changed
