Re: [PATCH v6] coresight: etm4x: avoid build failure with unrolled loops

From: Suzuki K Poulose
Date: Mon Jul 11 2022 - 04:35:57 EST

On 10/07/2022 20:13, Arnd Bergmann wrote:
On Sat, Jul 9, 2022 at 1:15 AM Nick Desaulniers <ndesaulniers@xxxxxxxxxx> wrote:

({ \
u64 __val; \
- if (__builtin_constant_p((offset))) \
+ if (__is_constexpr((offset))) \
__val = read_etm4x_sysreg_const_offset((offset)); \
else \
__val = etm4x_sysreg_read((offset), true, (_64bit)); \

This is clearly better than the current version using
__builtin_constant_p(), but
I don't think it's safe in all cases, since there are expressions that
are constant
expressions to the compiler but are not valid input to the assembler.

I would prefer to see this fixed differently, but doing this one first is also
fine with me:

Acked-by: Arnd Bergmann <arnd@xxxxxxxx>


Thanks, I have queued this.