diff options
Diffstat (limited to 'arch/s390/lib')
| -rw-r--r-- | arch/s390/lib/Makefile | 2 | ||||
| -rw-r--r-- | arch/s390/lib/qrnnd.S | 77 |
2 files changed, 78 insertions, 1 deletions
diff --git a/arch/s390/lib/Makefile b/arch/s390/lib/Makefile index b5f94cf3bde..7a44fed21b3 100644 --- a/arch/s390/lib/Makefile +++ b/arch/s390/lib/Makefile @@ -4,7 +4,7 @@ EXTRA_AFLAGS := -traditional -lib-y += delay.o string.o uaccess_std.o uaccess_pt.o +lib-y += delay.o string.o uaccess_std.o uaccess_pt.o qrnnd.o lib-$(CONFIG_32BIT) += div64.o lib-$(CONFIG_64BIT) += uaccess_mvcos.o lib-$(CONFIG_SMP) += spinlock.o diff --git a/arch/s390/lib/qrnnd.S b/arch/s390/lib/qrnnd.S new file mode 100644 index 00000000000..eb1df632e74 --- /dev/null +++ b/arch/s390/lib/qrnnd.S @@ -0,0 +1,77 @@ +# S/390 __udiv_qrnnd + +# r2 : &__r +# r3 : upper half of 64 bit word n +# r4 : lower half of 64 bit word n +# r5 : divisor d +# the reminder r of the division is to be stored to &__r and +# the quotient q is to be returned + + .text + .globl __udiv_qrnnd +__udiv_qrnnd: + st %r2,24(%r15) # store pointer to reminder for later + lr %r0,%r3 # reload n + lr %r1,%r4 + ltr %r2,%r5 # reload and test divisor + jp 5f + # divisor >= 0x80000000 + srdl %r0,2 # n/4 + srl %r2,1 # d/2 + slr %r1,%r2 # special case if last bit of d is set + brc 3,0f # (n/4) div (n/2) can overflow by 1 + ahi %r0,-1 # trick: subtract n/2, then divide +0: dr %r0,%r2 # signed division + ahi %r1,1 # trick part 2: add 1 to the quotient + # now (n >> 2) = (d >> 1) * %r1 + %r0 + lhi %r3,1 + nr %r3,%r1 # test last bit of q + jz 1f + alr %r0,%r2 # add (d>>1) to r +1: srl %r1,1 # q >>= 1 + # now (n >> 2) = (d&-2) * %r1 + %r0 + lhi %r3,1 + nr %r3,%r5 # test last bit of d + jz 2f + slr %r0,%r1 # r -= q + brc 3,2f # borrow ? + alr %r0,%r5 # r += d + ahi %r1,-1 +2: # now (n >> 2) = d * %r1 + %r0 + alr %r1,%r1 # q <<= 1 + alr %r0,%r0 # r <<= 1 + brc 12,3f # overflow on r ? + slr %r0,%r5 # r -= d + ahi %r1,1 # q += 1 +3: lhi %r3,2 + nr %r3,%r4 # test next to last bit of n + jz 4f + ahi %r0,1 # r += 1 +4: clr %r0,%r5 # r >= d ? + jl 6f + slr %r0,%r5 # r -= d + ahi %r1,1 # q += 1 + # now (n >> 1) = d * %r1 + %r0 + j 6f +5: # divisor < 0x80000000 + srdl %r0,1 + dr %r0,%r2 # signed division + # now (n >> 1) = d * %r1 + %r0 +6: alr %r1,%r1 # q <<= 1 + alr %r0,%r0 # r <<= 1 + brc 12,7f # overflow on r ? + slr %r0,%r5 # r -= d + ahi %r1,1 # q += 1 +7: lhi %r3,1 + nr %r3,%r4 # isolate last bit of n + alr %r0,%r3 # r += (n & 1) + clr %r0,%r5 # r >= d ? + jl 8f + slr %r0,%r5 # r -= d + ahi %r1,1 # q += 1 +8: # now n = d * %r1 + %r0 + l %r2,24(%r15) + st %r0,0(%r2) + lr %r2,%r1 + br %r14 + .end __udiv_qrnnd |