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charset="utf-8" Use __assume() to tell compilers that the output operand of the __flogr() inline assembly contains a value in the range of 0..64. This allows to optimize the logical AND operation away. This reduces the kernel image size by 2804 bytes (defconfig, gcc 15.2.0). Suggested-by: Juergen Christ Reviewed-by: Juergen Christ Signed-off-by: Heiko Carstens --- arch/s390/include/asm/bitops.h | 14 +++++++++++--- 1 file changed, 11 insertions(+), 3 deletions(-) diff --git a/arch/s390/include/asm/bitops.h b/arch/s390/include/asm/bitops.h index a1dd72b16f54..5ff069fe9526 100644 --- a/arch/s390/include/asm/bitops.h +++ b/arch/s390/include/asm/bitops.h @@ -132,9 +132,10 @@ static inline bool test_bit_inv(unsigned long nr, */ static __always_inline unsigned char __flogr(unsigned long word) { - if (__builtin_constant_p(word)) { - unsigned long bit =3D 0; + unsigned long bit; =20 + if (__builtin_constant_p(word)) { + bit =3D 0; if (!word) return 64; if (!(word & 0xffffffff00000000UL)) { @@ -169,7 +170,14 @@ static __always_inline unsigned char __flogr(unsigned = long word) asm volatile( " flogr %[rp],%[rp]\n" : [rp] "+d" (rp.pair) : : "cc"); - return rp.even & 127; + bit =3D rp.even; + /* + * The result of the flogr instruction is a value in the range + * of 0..64. Let the compiler know that the AND operation can + * be optimized away. + */ + __assume(bit <=3D 64); + return bit & 127; } } =20 --=20 2.48.1