[PATCH v2 1/2] ARM: drop WASM to work around LLVM issue
stefan at agner.ch
Tue Mar 19 15:07:35 PDT 2019
On 18.03.2019 19:09, Nick Desaulniers wrote:
> On Sun, Mar 17, 2019 at 4:05 PM Stefan Agner <stefan at agner.ch> wrote:
>> Currently LLVM's integrated assembler does not recognize .w form
>> of the pld instructions (LLVM Bug 40972 ):
>> ./arch/arm/include/asm/processor.h:133:5: error: invalid instruction
>> "pldw.w\t%a0 \n"
>> <inline asm>:2:1: note: instantiated into assembly here
>> pldw.w [r0]
>> 1 error generated.
>> The W macro for generating wide instructions when targeting Thumb-2
>> is not strictly required for the preload data instructions (pld, pldw)
>> since they are only available as wide instructions. The GNU assembler
>> works with or without the .w appended when compiling an Thumb-2 kernel.
>> Drop the macro to work around LLVM Bug 40972 issue.
>>  https://bugs.llvm.org/show_bug.cgi?id=40972
>> Signed-off-by: Stefan Agner <stefan at agner.ch>
> Thanks for the bug report and patch.
> Reviewed-by: Nick Desaulniers <ndesaulniers at google.com>
> Just curious, there are only 3 other expansion sites of this macro.
> Are any of those problematic? Looks like nop.w, sev.w and b.w?
All three sites are in inline assembly, and I did a bunch of successful
Thumb2 builds using the integrated assembler, so I think all those sites
have been assembled by LLVM successfully.
Also confirmed those three instructions with the reproducer example from
the LLVM bug above.
>> Changes in v2:
>> - Reword commit message to reflect the fact that this is a work around
>> for LLVM.
>> arch/arm/include/asm/processor.h | 4 ++--
>> 1 file changed, 2 insertions(+), 2 deletions(-)
>> diff --git a/arch/arm/include/asm/processor.h b/arch/arm/include/asm/processor.h
>> index 57fe73ea0f72..5d06f75ffad4 100644
>> --- a/arch/arm/include/asm/processor.h
>> +++ b/arch/arm/include/asm/processor.h
>> @@ -135,8 +135,8 @@ static inline void prefetchw(const void *ptr)
>> __asm__ __volatile__(
>> ".arch_extension mp\n"
>> - WASM(pldw) "\t%a0",
>> - WASM(pld) "\t%a0"
>> + "pldw\t%a0",
>> + "pld\t%a0"
>> :: "p" (ptr));
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