| Message ID | 20191002180047.17144-3-julien.grall@arm.com |
|---|---|
| State | New |
| Headers | show |
| Series | xen/arm: Add support to build with clang | expand |
On Wed, 2 Oct 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 instruction clz is expecting the two operands to be the same size > (i.e 32-bit or 64-bit). As the flsl function is dealing with 64-bit > value, we need to make the destination variable 64-bit as well. > > While at it, add a newline before the return statement. > > Note that the return type of flsl is not updated because the result will > always be smaller than 64 and therefore fit in 32-bit. > > Signed-off-by: Julien Grall <julien.grall@arm.com> Acked-by: Stefano Stabellini <sstabellini@kernel.org> > --- > Changes in v2: > - Update the commit message to explain why the return type is > not modified > --- > xen/include/asm-arm/arm64/bitops.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/xen/include/asm-arm/arm64/bitops.h b/xen/include/asm-arm/arm64/bitops.h > index 6cc224ad13..d85a49bca4 100644 > --- a/xen/include/asm-arm/arm64/bitops.h > +++ b/xen/include/asm-arm/arm64/bitops.h > @@ -24,12 +24,13 @@ static /*__*/always_inline unsigned long __ffs(unsigned long word) > > static inline int flsl(unsigned long x) > { > - int ret; > + uint64_t ret; > > if (__builtin_constant_p(x)) > return generic_flsl(x); > > asm("clz\t%0, %1" : "=r" (ret) : "r" (x)); > + > return BITS_PER_LONG - ret; > } > > -- > 2.11.0 >
diff --git a/xen/include/asm-arm/arm64/bitops.h b/xen/include/asm-arm/arm64/bitops.h index 6cc224ad13..d85a49bca4 100644 --- a/xen/include/asm-arm/arm64/bitops.h +++ b/xen/include/asm-arm/arm64/bitops.h @@ -24,12 +24,13 @@ static /*__*/always_inline unsigned long __ffs(unsigned long word) static inline int flsl(unsigned long x) { - int ret; + uint64_t ret; if (__builtin_constant_p(x)) return generic_flsl(x); asm("clz\t%0, %1" : "=r" (ret) : "r" (x)); + return BITS_PER_LONG - ret; }
Clang is pickier than GCC for the register size in asm statement. It expects the register size to match the value size. The instruction clz is expecting the two operands to be the same size (i.e 32-bit or 64-bit). As the flsl function is dealing with 64-bit value, we need to make the destination variable 64-bit as well. While at it, add a newline before the return statement. Note that the return type of flsl is not updated because the result will always be smaller than 64 and therefore fit in 32-bit. Signed-off-by: Julien Grall <julien.grall@arm.com> --- Changes in v2: - Update the commit message to explain why the return type is not modified --- xen/include/asm-arm/arm64/bitops.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)