| Message ID | 20191002180047.17144-4-julien.grall@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/arm: Add support to build with clang | expand |
On 02/10/2019 19:00, Julien Grall wrote: > Clang is pickier than GCC for the register size in asm statement. It > expects the register size to match the value size. > > The asm statement expects a 32-bit (resp. 64-bit) value on Arm32 > (resp. Arm64) whereas the value is a boolean (Clang consider to be > 32-bit). > > It would be possible to impose 32-bit register for both architecture > but this require the code to use __OP32. However, it does not really > improve the assembly generated. Instead, replace switch the variable > to use register_t. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > > --- > Changes in v2: > - Use !! per Stefano's request You are aware that unlikley(), deliberately, has an embedded !! ? include/xen/compiler.h:11:#define unlikely(x) __builtin_expect(!!(x),0) ~Andrew
Hi Andrew, On 10/2/19 7:42 PM, Andrew Cooper wrote: > On 02/10/2019 19:00, Julien Grall wrote: >> Clang is pickier than GCC for the register size in asm statement. It >> expects the register size to match the value size. >> >> The asm statement expects a 32-bit (resp. 64-bit) value on Arm32 >> (resp. Arm64) whereas the value is a boolean (Clang consider to be >> 32-bit). >> >> It would be possible to impose 32-bit register for both architecture >> but this require the code to use __OP32. However, it does not really >> improve the assembly generated. Instead, replace switch the variable >> to use register_t. >> >> Signed-off-by: Julien Grall <julien.grall@arm.com> >> >> --- >> Changes in v2: >> - Use !! per Stefano's request > > You are aware that unlikley(), deliberately, has an embedded !! ? I forgot it, sorry about that :/. Stefano are you happy if I revert to v1? > > include/xen/compiler.h:11:#define unlikely(x) __builtin_expect(!!(x),0) > > ~Andrew > Cheers,
On Wed, 2 Oct 2019, Julien Grall wrote: > Hi Andrew, > > On 10/2/19 7:42 PM, Andrew Cooper wrote: > > On 02/10/2019 19:00, Julien Grall wrote: > > > Clang is pickier than GCC for the register size in asm statement. It > > > expects the register size to match the value size. > > > > > > The asm statement expects a 32-bit (resp. 64-bit) value on Arm32 > > > (resp. Arm64) whereas the value is a boolean (Clang consider to be > > > 32-bit). > > > > > > It would be possible to impose 32-bit register for both architecture > > > but this require the code to use __OP32. However, it does not really > > > improve the assembly generated. Instead, replace switch the variable > > > to use register_t. > > > > > > Signed-off-by: Julien Grall <julien.grall@arm.com> > > > > > > --- > > > Changes in v2: > > > - Use !! per Stefano's request > > > > You are aware that unlikley(), deliberately, has an embedded !! ? > > I forgot it, sorry about that :/. Stefano are you happy if I revert to v1? I forgot about that too. Yes, that's fine and add my acked-by. > > > > include/xen/compiler.h:11:#define unlikely(x) __builtin_expect(!!(x),0) > > > > ~Andrew
diff --git a/xen/include/asm-arm/cpuerrata.h b/xen/include/asm-arm/cpuerrata.h index 55ddfda272..0896fe6e25 100644 --- a/xen/include/asm-arm/cpuerrata.h +++ b/xen/include/asm-arm/cpuerrata.h @@ -14,14 +14,14 @@ static inline bool check_workaround_##erratum(void) \ return false; \ else \ { \ - bool ret; \ + register_t ret; \ \ asm volatile (ALTERNATIVE("mov %0, #0", \ "mov %0, #1", \ feature) \ : "=r" (ret)); \ \ - return unlikely(ret); \ + return unlikely(!!ret); \ } \ }
Clang is pickier than GCC for the register size in asm statement. It expects the register size to match the value size. The asm statement expects a 32-bit (resp. 64-bit) value on Arm32 (resp. Arm64) whereas the value is a boolean (Clang consider to be 32-bit). It would be possible to impose 32-bit register for both architecture but this require the code to use __OP32. However, it does not really improve the assembly generated. Instead, replace switch the variable to use register_t. Signed-off-by: Julien Grall <julien.grall@arm.com> --- Changes in v2: - Use !! per Stefano's request --- xen/include/asm-arm/cpuerrata.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)