Re: [PATCH v2 11/18] arm64: make mrs_s and msr_s macros work with LTO

From: Yury Norov
Date: Thu Nov 16 2017 - 08:08:16 EST

On Thu, Nov 16, 2017 at 11:54:33AM +0000, Will Deacon wrote:
> On Wed, Nov 15, 2017 at 01:34:21PM -0800, Sami Tolvanen wrote:
> > From: Alex Matveev <alxmtvv@xxxxxxxxx>
> >
> > Use UNDEFINE_MRS_S and UNDEFINE_MSR_S to define corresponding macros
> > in-place and workaround gcc and clang limitations on redefining macros
> > across different assembler blocks.
> What limitations? Can you elaborate please? Is this a fix?

Hi Will,

Regarding GCC.

When it joins preprocessed source files into single asm file,
mrs_s/msr_s becomes either not declared or declared multiple times.

./ccuFb68h.s:33120: Error: Macro `mrs_s' was already defined
./ccuFb68h.s:33124: Error: Macro `msr_s' was already defined

I'm not sure that GCC works correctly in this case, and I sent the
email to Linaro toolchain group to clarify it. See below.



My unfinished branch:
Andi Kleen tree:
Sami Tolvanen's recent work for clang:

Question we have for now:
There's mrs_s/msr_s macro that doesn't work with LTO - linker
complains very loudly that macro is either not declared, or declared
multiple times. (To reproduce - try to build my kernel branch w/o last

The same (?) problem is observed with clang, and people there
considered it as feature, not a bug.

We have the fix for both clang and gcc, but it looks hacky. Maybe it
worth to fix mrs/msr issue on toolchain side?