1 files changed, 77 insertions, 0 deletions
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