From: David Howells This facility provides three entry points: ilog2() Log base 2 of unsigned long ilog2_u32() Log base 2 of u32 ilog2_u64() Log base 2 of u64 These facilities can either be used inside functions on dynamic data: int do_something(long q) { ...; y = ilog2(x) ...; } Or can be used to statically initialise global variables with constant values: unsigned n = ilog2(27); When performing static initialisation, the compiler will report "error: initializer element is not constant" if asked to take a log of zero or of something not reducible to a constant. They treat negative numbers as unsigned. When not dealing with a constant, they fall back to using fls() which permits them to use arch-specific log calculation instructions - such as BSR on x86/x86_64 or SCAN on FRV - if available. Signed-off-by: David Howells Cc: Benjamin Herrenschmidt Cc: Paul Mackerras Signed-off-by: Andrew Morton --- arch/alpha/Kconfig | 8 + arch/arm/Kconfig | 8 + arch/arm26/Kconfig | 8 + arch/avr32/Kconfig | 8 + arch/cris/Kconfig | 8 + arch/frv/Kconfig | 8 + arch/h8300/Kconfig | 8 + arch/i386/Kconfig.cpu | 8 + arch/ia64/Kconfig | 8 + arch/m32r/Kconfig | 8 + arch/m68k/Kconfig | 8 + arch/m68knommu/Kconfig | 8 + arch/mips/Kconfig | 8 + arch/parisc/Kconfig | 8 + arch/powerpc/Kconfig | 8 + arch/ppc/Kconfig | 8 + arch/s390/Kconfig | 8 + arch/sh/Kconfig | 8 + arch/sh64/Kconfig | 8 + arch/sparc/Kconfig | 8 + arch/sparc64/Kconfig | 8 + arch/v850/Kconfig | 8 + arch/x86_64/Kconfig | 8 + arch/xtensa/Kconfig | 8 + drivers/infiniband/hw/mthca/mthca_provider.c | 4 drivers/infiniband/hw/mthca/mthca_qp.c | 4 drivers/infiniband/hw/mthca/mthca_srq.c | 4 drivers/infiniband/ulp/iser/iser_memory.c | 4 fs/ext2/super.c | 6 fs/ext3/super.c | 6 include/asm-frv/bitops.h | 44 +++++ include/linux/kernel.h | 9 - include/linux/log2.h | 131 +++++++++++++++++ mm/page_alloc.c | 4 34 files changed, 382 insertions(+), 26 deletions(-) diff -puN arch/alpha/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/alpha/Kconfig --- a/arch/alpha/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/alpha/Kconfig @@ -25,6 +25,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/arm/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/arm/Kconfig --- a/arch/arm/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/arm/Kconfig @@ -75,6 +75,14 @@ config RWSEM_GENERIC_SPINLOCK config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_HWEIGHT bool default y diff -puN arch/arm26/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/arm26/Kconfig --- a/arch/arm26/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/arm26/Kconfig @@ -41,6 +41,14 @@ config RWSEM_GENERIC_SPINLOCK config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_HWEIGHT bool default y diff -puN arch/avr32/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/avr32/Kconfig --- a/arch/avr32/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/avr32/Kconfig @@ -45,6 +45,14 @@ config GENERIC_TIME config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_BUST_SPINLOCK bool diff -puN arch/cris/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/cris/Kconfig --- a/arch/cris/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/cris/Kconfig @@ -20,6 +20,14 @@ config RWSEM_GENERIC_SPINLOCK config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/frv/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/frv/Kconfig --- a/arch/frv/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/frv/Kconfig @@ -45,6 +45,14 @@ config TIME_LOW_RES bool default y +config ARCH_HAS_ILOG2_U32 + bool + default y + +config ARCH_HAS_ILOG2_U64 + bool + default y + mainmenu "Fujitsu FR-V Kernel Configuration" source "init/Kconfig" diff -puN arch/h8300/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/h8300/Kconfig --- a/arch/h8300/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/h8300/Kconfig @@ -33,6 +33,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default n +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/i386/Kconfig.cpu~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/i386/Kconfig.cpu --- a/arch/i386/Kconfig.cpu~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/i386/Kconfig.cpu @@ -241,6 +241,14 @@ config RWSEM_XCHGADD_ALGORITHM depends on !M386 default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_CALIBRATE_DELAY bool default y diff -puN arch/ia64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/ia64/Kconfig --- a/arch/ia64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/ia64/Kconfig @@ -38,6 +38,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/m32r/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/m32r/Kconfig --- a/arch/m32r/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/m32r/Kconfig @@ -218,6 +218,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default n +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/m68k/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/m68k/Kconfig --- a/arch/m68k/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/m68k/Kconfig @@ -17,6 +17,14 @@ config RWSEM_GENERIC_SPINLOCK config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_HWEIGHT bool default y diff -puN arch/m68knommu/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/m68knommu/Kconfig --- a/arch/m68knommu/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/m68knommu/Kconfig @@ -29,6 +29,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default n +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/mips/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/mips/Kconfig --- a/arch/mips/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/mips/Kconfig @@ -793,6 +793,14 @@ config RWSEM_GENERIC_SPINLOCK config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/parisc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/parisc/Kconfig --- a/arch/parisc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/parisc/Kconfig @@ -25,6 +25,14 @@ config RWSEM_GENERIC_SPINLOCK config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_FIND_NEXT_BIT bool default y diff -puN arch/powerpc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/powerpc/Kconfig --- a/arch/powerpc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/powerpc/Kconfig @@ -41,6 +41,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_HWEIGHT bool default y diff -puN arch/ppc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/ppc/Kconfig --- a/arch/ppc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/ppc/Kconfig @@ -19,6 +19,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_HWEIGHT bool default y diff -puN arch/s390/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/s390/Kconfig --- a/arch/s390/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/s390/Kconfig @@ -26,6 +26,14 @@ config RWSEM_XCHGADD_ALGORITHM bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config GENERIC_HWEIGHT bool default y diff -puN arch/sh/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/sh/Kconfig --- a/arch/sh/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/sh/Kconfig @@ -51,6 +51,14 @@ config GENERIC_TIME config ARCH_MAY_HAVE_PC_FDC bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + source "init/Kconfig" menu "System type" diff -puN arch/sh64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/sh64/Kconfig --- a/arch/sh64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/sh64/Kconfig @@ -36,6 +36,14 @@ config GENERIC_CALIBRATE_DELAY config RWSEM_XCHGADD_ALGORITHM bool +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + source init/Kconfig menu "System type" diff -puN arch/sparc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/sparc/Kconfig --- a/arch/sparc/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/sparc/Kconfig @@ -170,6 +170,14 @@ config ARCH_MAY_HAVE_PC_FDC bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config SUN_PM bool default y diff -puN arch/sparc64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/sparc64/Kconfig --- a/arch/sparc64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/sparc64/Kconfig @@ -34,6 +34,14 @@ config ARCH_MAY_HAVE_PC_FDC bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + config AUDIT_ARCH bool default y diff -puN arch/v850/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/v850/Kconfig --- a/arch/v850/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/v850/Kconfig @@ -41,6 +41,14 @@ config TIME_LOW_RES bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + # Turn off some random 386 crap that can affect device config config ISA bool diff -puN arch/x86_64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/x86_64/Kconfig --- a/arch/x86_64/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/x86_64/Kconfig @@ -105,6 +105,14 @@ config GENERIC_BUG default y depends on BUG +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + source "init/Kconfig" diff -puN arch/xtensa/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel arch/xtensa/Kconfig --- a/arch/xtensa/Kconfig~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/arch/xtensa/Kconfig @@ -38,6 +38,14 @@ config GENERIC_HARDIRQS bool default y +config ARCH_HAS_ILOG2_U32 + bool + default n + +config ARCH_HAS_ILOG2_U64 + bool + default n + source "init/Kconfig" menu "Processor type and features" diff -puN drivers/infiniband/hw/mthca/mthca_provider.c~log2-implement-a-general-integer-log2-facility-in-the-kernel drivers/infiniband/hw/mthca/mthca_provider.c --- a/drivers/infiniband/hw/mthca/mthca_provider.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/drivers/infiniband/hw/mthca/mthca_provider.c @@ -124,7 +124,7 @@ static int mthca_query_device(struct ib_ props->max_map_per_fmr = 255; else props->max_map_per_fmr = - (1 << (32 - long_log2(mdev->limits.num_mpts))) - 1; + (1 << (32 - ilog2(mdev->limits.num_mpts))) - 1; err = 0; out: @@ -816,7 +816,7 @@ static int mthca_resize_cq(struct ib_cq lkey = ucmd.lkey; } - ret = mthca_RESIZE_CQ(dev, cq->cqn, lkey, long_log2(entries), &status); + ret = mthca_RESIZE_CQ(dev, cq->cqn, lkey, ilog2(entries), &status); if (status) ret = -EINVAL; diff -puN drivers/infiniband/hw/mthca/mthca_qp.c~log2-implement-a-general-integer-log2-facility-in-the-kernel drivers/infiniband/hw/mthca/mthca_qp.c --- a/drivers/infiniband/hw/mthca/mthca_qp.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/drivers/infiniband/hw/mthca/mthca_qp.c @@ -637,11 +637,11 @@ int mthca_modify_qp(struct ib_qp *ibqp, if (mthca_is_memfree(dev)) { if (qp->rq.max) - qp_context->rq_size_stride = long_log2(qp->rq.max) << 3; + qp_context->rq_size_stride = ilog2(qp->rq.max) << 3; qp_context->rq_size_stride |= qp->rq.wqe_shift - 4; if (qp->sq.max) - qp_context->sq_size_stride = long_log2(qp->sq.max) << 3; + qp_context->sq_size_stride = ilog2(qp->sq.max) << 3; qp_context->sq_size_stride |= qp->sq.wqe_shift - 4; } diff -puN drivers/infiniband/hw/mthca/mthca_srq.c~log2-implement-a-general-integer-log2-facility-in-the-kernel drivers/infiniband/hw/mthca/mthca_srq.c --- a/drivers/infiniband/hw/mthca/mthca_srq.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/drivers/infiniband/hw/mthca/mthca_srq.c @@ -120,7 +120,7 @@ static void mthca_arbel_init_srq_context memset(context, 0, sizeof *context); - logsize = long_log2(srq->max) + srq->wqe_shift; + logsize = ilog2(srq->max) + srq->wqe_shift; context->state_logsize_srqn = cpu_to_be32(logsize << 24 | srq->srqn); context->lkey = cpu_to_be32(srq->mr.ibmr.lkey); context->db_index = cpu_to_be32(srq->db_index); @@ -213,7 +213,7 @@ int mthca_alloc_srq(struct mthca_dev *de if (!mthca_is_memfree(dev) && (ds > dev->limits.max_desc_sz)) return -EINVAL; - srq->wqe_shift = long_log2(ds); + srq->wqe_shift = ilog2(ds); srq->srqn = mthca_alloc(&dev->srq_table.alloc); if (srq->srqn == -1) diff -puN drivers/infiniband/ulp/iser/iser_memory.c~log2-implement-a-general-integer-log2-facility-in-the-kernel drivers/infiniband/ulp/iser/iser_memory.c --- a/drivers/infiniband/ulp/iser/iser_memory.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/drivers/infiniband/ulp/iser/iser_memory.c @@ -113,7 +113,7 @@ int iser_start_rdma_unaligned_sg(struct if (cmd_data_len > ISER_KMALLOC_THRESHOLD) mem = (void *)__get_free_pages(GFP_NOIO, - long_log2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT); + ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT); else mem = kmalloc(cmd_data_len, GFP_NOIO); @@ -210,7 +210,7 @@ void iser_finalize_rdma_unaligned_sg(str if (cmd_data_len > ISER_KMALLOC_THRESHOLD) free_pages((unsigned long)mem_copy->copy_buf, - long_log2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT); + ilog2(roundup_pow_of_two(cmd_data_len)) - PAGE_SHIFT); else kfree(mem_copy->copy_buf); diff -puN fs/ext2/super.c~log2-implement-a-general-integer-log2-facility-in-the-kernel fs/ext2/super.c --- a/fs/ext2/super.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/fs/ext2/super.c @@ -597,8 +597,6 @@ static int ext2_check_descriptors (struc return 1; } -#define log2(n) ffz(~(n)) - /* * Maximal file size. There is a direct, and {,double-,triple-}indirect * block limit, and also a limit of (2^32 - 1) 512-byte sectors in i_blocks. @@ -834,9 +832,9 @@ static int ext2_fill_super(struct super_ sbi->s_sbh = bh; sbi->s_mount_state = le16_to_cpu(es->s_state); sbi->s_addr_per_block_bits = - log2 (EXT2_ADDR_PER_BLOCK(sb)); + ilog2 (EXT2_ADDR_PER_BLOCK(sb)); sbi->s_desc_per_block_bits = - log2 (EXT2_DESC_PER_BLOCK(sb)); + ilog2 (EXT2_DESC_PER_BLOCK(sb)); if (sb->s_magic != EXT2_SUPER_MAGIC) goto cantfind_ext2; diff -puN fs/ext3/super.c~log2-implement-a-general-integer-log2-facility-in-the-kernel fs/ext3/super.c --- a/fs/ext3/super.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/fs/ext3/super.c @@ -1341,8 +1341,6 @@ static void ext3_orphan_cleanup (struct sb->s_flags = s_flags; /* Restore MS_RDONLY status */ } -#define log2(n) ffz(~(n)) - /* * Maximal file size. There is a direct, and {,double-,triple-}indirect * block limit, and also a limit of (2^32 - 1) 512-byte sectors in i_blocks. @@ -1591,8 +1589,8 @@ static int ext3_fill_super (struct super sbi->s_desc_per_block = blocksize / sizeof(struct ext3_group_desc); sbi->s_sbh = bh; sbi->s_mount_state = le16_to_cpu(es->s_state); - sbi->s_addr_per_block_bits = log2(EXT3_ADDR_PER_BLOCK(sb)); - sbi->s_desc_per_block_bits = log2(EXT3_DESC_PER_BLOCK(sb)); + sbi->s_addr_per_block_bits = ilog2(EXT3_ADDR_PER_BLOCK(sb)); + sbi->s_desc_per_block_bits = ilog2(EXT3_DESC_PER_BLOCK(sb)); for (i=0; i < 4; i++) sbi->s_hash_seed[i] = le32_to_cpu(es->s_hash_seed[i]); sbi->s_def_hash_version = es->s_def_hash_version; diff -puN include/asm-frv/bitops.h~log2-implement-a-general-integer-log2-facility-in-the-kernel include/asm-frv/bitops.h --- a/include/asm-frv/bitops.h~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/include/asm-frv/bitops.h @@ -256,6 +256,50 @@ int __ffs(unsigned long x) return 31 - bit; } +/* + * special slimline version of fls() for calculating ilog2_u32() + * - note: no protection against n == 0 + */ +#define ARCH_HAS_ILOG2_U32 +static inline __attribute__((const)) +int __ilog2_u32(u32 n) +{ + int bit; + asm("scan %1,gr0,%0" : "=r"(bit) : "r"(n)); + return 31 - bit; +} + +/* + * special slimline version of fls64() for calculating ilog2_u64() + * - note: no protection against n == 0 + */ +#define ARCH_HAS_ILOG2_U64 +static inline __attribute__((const)) +int __ilog2_u64(u64 n) +{ + union { + u64 ll; + struct { u32 h, l; }; + } _; + int bit, x, y; + + _.ll = n; + + asm(" subcc %3,gr0,gr0,icc0 \n" + " ckeq icc0,cc4 \n" + " cscan.p %3,gr0,%0 ,cc4,0 \n" + " setlos #63,%1 \n" + " cscan.p %4,gr0,%0 ,cc4,1 \n" + " setlos #31,%2 \n" + " csub.p %1,%0,%0 ,cc4,0 \n" + " csub %2,%0,%0 ,cc4,1 \n" + : "=&r"(bit), "=r"(x), "=r"(y) + : "0r"(_.h), "r"(_.l) + : "icc0", "cc4" + ); + return bit; +} + #include #include diff -puN include/linux/kernel.h~log2-implement-a-general-integer-log2-facility-in-the-kernel include/linux/kernel.h --- a/include/linux/kernel.h~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/include/linux/kernel.h @@ -13,6 +13,7 @@ #include #include #include +#include #include #include @@ -155,14 +156,6 @@ static inline int printk(const char *s, unsigned long int_sqrt(unsigned long); -static inline int __attribute_pure__ long_log2(unsigned long x) -{ - int r = 0; - for (x >>= 1; x > 0; x >>= 1) - r++; - return r; -} - static inline unsigned long __attribute_const__ roundup_pow_of_two(unsigned long x) { diff -puN /dev/null include/linux/log2.h --- /dev/null +++ a/include/linux/log2.h @@ -0,0 +1,131 @@ +/* Integer base 2 logarithm calculation + * + * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + * + * This program is free software; you can redistribute it and/or + * modify it under the terms of the GNU General Public License + * as published by the Free Software Foundation; either version + * 2 of the License, or (at your option) any later version. + */ + +#ifndef _LINUX_LOG2_H +#define _LINUX_LOG2_H + +#include +#include + +/* + * deal with unrepresentable constant logarithms + */ +extern __attribute__((const, noreturn)) +int ____ilog2_NaN(void); + +/* + * non-constant log of base 2 calculators + * - the arch may override these in asm/bitops.h if they can be implemented + * more efficiently than using fls() and fls64() + * - the arch is not required to handle n==0 if implementing the fallback + */ +#ifndef CONFIG_ARCH_HAS_ILOG2_U32 +static inline __attribute__((const)) +int __ilog2_u32(u32 n) +{ + return fls(n) - 1; +} +#endif + +#ifndef CONFIG_ARCH_HAS_ILOG2_U64 +static inline __attribute__((const)) +int __ilog2_u64(u64 n) +{ + return fls64(n) - 1; +} +#endif + +/** + * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value + * @n - parameter + * + * constant-capable log of base 2 calculation + * - this can be used to initialise global variables from constant data, hence + * the massive ternary operator construction + * + * selects the appropriately-sized optimised version depending on sizeof(n) + */ +#define ilog2(n) \ +( \ + __builtin_constant_p(n) ? ( \ + (n) < 1 ? ____ilog2_NaN() : \ + (n) & (1ULL << 63) ? 63 : \ + (n) & (1ULL << 62) ? 62 : \ + (n) & (1ULL << 61) ? 61 : \ + (n) & (1ULL << 60) ? 60 : \ + (n) & (1ULL << 59) ? 59 : \ + (n) & (1ULL << 58) ? 58 : \ + (n) & (1ULL << 57) ? 57 : \ + (n) & (1ULL << 56) ? 56 : \ + (n) & (1ULL << 55) ? 55 : \ + (n) & (1ULL << 54) ? 54 : \ + (n) & (1ULL << 53) ? 53 : \ + (n) & (1ULL << 52) ? 52 : \ + (n) & (1ULL << 51) ? 51 : \ + (n) & (1ULL << 50) ? 50 : \ + (n) & (1ULL << 49) ? 49 : \ + (n) & (1ULL << 48) ? 48 : \ + (n) & (1ULL << 47) ? 47 : \ + (n) & (1ULL << 46) ? 46 : \ + (n) & (1ULL << 45) ? 45 : \ + (n) & (1ULL << 44) ? 44 : \ + (n) & (1ULL << 43) ? 43 : \ + (n) & (1ULL << 42) ? 42 : \ + (n) & (1ULL << 41) ? 41 : \ + (n) & (1ULL << 40) ? 40 : \ + (n) & (1ULL << 39) ? 39 : \ + (n) & (1ULL << 38) ? 38 : \ + (n) & (1ULL << 37) ? 37 : \ + (n) & (1ULL << 36) ? 36 : \ + (n) & (1ULL << 35) ? 35 : \ + (n) & (1ULL << 34) ? 34 : \ + (n) & (1ULL << 33) ? 33 : \ + (n) & (1ULL << 32) ? 32 : \ + (n) & (1ULL << 31) ? 31 : \ + (n) & (1ULL << 30) ? 30 : \ + (n) & (1ULL << 29) ? 29 : \ + (n) & (1ULL << 28) ? 28 : \ + (n) & (1ULL << 27) ? 27 : \ + (n) & (1ULL << 26) ? 26 : \ + (n) & (1ULL << 25) ? 25 : \ + (n) & (1ULL << 24) ? 24 : \ + (n) & (1ULL << 23) ? 23 : \ + (n) & (1ULL << 22) ? 22 : \ + (n) & (1ULL << 21) ? 21 : \ + (n) & (1ULL << 20) ? 20 : \ + (n) & (1ULL << 19) ? 19 : \ + (n) & (1ULL << 18) ? 18 : \ + (n) & (1ULL << 17) ? 17 : \ + (n) & (1ULL << 16) ? 16 : \ + (n) & (1ULL << 15) ? 15 : \ + (n) & (1ULL << 14) ? 14 : \ + (n) & (1ULL << 13) ? 13 : \ + (n) & (1ULL << 12) ? 12 : \ + (n) & (1ULL << 11) ? 11 : \ + (n) & (1ULL << 10) ? 10 : \ + (n) & (1ULL << 9) ? 9 : \ + (n) & (1ULL << 8) ? 8 : \ + (n) & (1ULL << 7) ? 7 : \ + (n) & (1ULL << 6) ? 6 : \ + (n) & (1ULL << 5) ? 5 : \ + (n) & (1ULL << 4) ? 4 : \ + (n) & (1ULL << 3) ? 3 : \ + (n) & (1ULL << 2) ? 2 : \ + (n) & (1ULL << 1) ? 1 : \ + (n) & (1ULL << 0) ? 0 : \ + ____ilog2_NaN() \ + ) : \ + (sizeof(n) <= 4) ? \ + __ilog2_u32(n) : \ + __ilog2_u64(n) \ + ) + +#endif /* _LINUX_LOG2_H */ diff -puN mm/page_alloc.c~log2-implement-a-general-integer-log2-facility-in-the-kernel mm/page_alloc.c --- a/mm/page_alloc.c~log2-implement-a-general-integer-log2-facility-in-the-kernel +++ a/mm/page_alloc.c @@ -3235,7 +3235,7 @@ void *__init alloc_large_system_hash(con if (numentries > max) numentries = max; - log2qty = long_log2(numentries); + log2qty = ilog2(numentries); do { size = bucketsize << log2qty; @@ -3257,7 +3257,7 @@ void *__init alloc_large_system_hash(con printk("%s hash table entries: %d (order: %d, %lu bytes)\n", tablename, (1U << log2qty), - long_log2(size) - PAGE_SHIFT, + ilog2(size) - PAGE_SHIFT, size); if (_hash_shift) _