| Message ID | 20190327184531.30986-9-julien.grall@arm.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | xen/arm: Add support to build with clang | expand |
On Wed, 27 Mar 2019, 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 no really > improve the assembly generated. Instead, replace switch the variable to > use register_t. > > Signed-off-by: Julien Grall <julien.grall@arm.com> > --- > xen/include/asm-arm/cpufeature.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h > index c2c8f3417c..d06f09ecfa 100644 > --- a/xen/include/asm-arm/cpufeature.h > +++ b/xen/include/asm-arm/cpufeature.h > @@ -67,7 +67,7 @@ static inline bool cpus_have_cap(unsigned int num) > > /* System capability check for constant cap */ > #define cpus_have_const_cap(num) ({ \ > - bool __ret; \ > + register_t __ret; \ > \ > asm volatile (ALTERNATIVE("mov %0, #0", \ > "mov %0, #1", \ As per the previous one, this is fine, but could you also change the last statement below to unlikely(!!__ret);
On 4/17/19 9:29 PM, Stefano Stabellini wrote: > On Wed, 27 Mar 2019, 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 no really >> improve the assembly generated. Instead, replace switch the variable to >> use register_t. >> >> Signed-off-by: Julien Grall <julien.grall@arm.com> >> --- >> xen/include/asm-arm/cpufeature.h | 2 +- >> 1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h >> index c2c8f3417c..d06f09ecfa 100644 >> --- a/xen/include/asm-arm/cpufeature.h >> +++ b/xen/include/asm-arm/cpufeature.h >> @@ -67,7 +67,7 @@ static inline bool cpus_have_cap(unsigned int num) >> >> /* System capability check for constant cap */ >> #define cpus_have_const_cap(num) ({ \ >> - bool __ret; \ >> + register_t __ret; \ >> \ >> asm volatile (ALTERNATIVE("mov %0, #0", \ >> "mov %0, #1", \ > > As per the previous one, this is fine, but could you also change the > last statement below to unlikely(!!__ret); As per the previous one, the current code is valid. Please justify why !! is necessary. Cheers,
diff --git a/xen/include/asm-arm/cpufeature.h b/xen/include/asm-arm/cpufeature.h index c2c8f3417c..d06f09ecfa 100644 --- a/xen/include/asm-arm/cpufeature.h +++ b/xen/include/asm-arm/cpufeature.h @@ -67,7 +67,7 @@ static inline bool cpus_have_cap(unsigned int num) /* System capability check for constant cap */ #define cpus_have_const_cap(num) ({ \ - bool __ret; \ + register_t __ret; \ \ asm volatile (ALTERNATIVE("mov %0, #0", \ "mov %0, #1", \
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 no really improve the assembly generated. Instead, replace switch the variable to use register_t. Signed-off-by: Julien Grall <julien.grall@arm.com> --- xen/include/asm-arm/cpufeature.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)