--- /dev/null
+dnl AMD K7 mpn_mod_1 -- mpn by limb remainder.
+
+dnl Copyright 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
+dnl
+dnl This file is part of the GNU MP Library.
+dnl
+dnl The GNU MP Library is free software; you can redistribute it and/or
+dnl modify it under the terms of the GNU Lesser General Public License as
+dnl published by the Free Software Foundation; either version 3 of the
+dnl License, or (at your option) any later version.
+dnl
+dnl The GNU MP Library is distributed in the hope that it will be useful,
+dnl but WITHOUT ANY WARRANTY; without even the implied warranty of
+dnl MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+dnl Lesser General Public License for more details.
+dnl
+dnl You should have received a copy of the GNU Lesser General Public License
+dnl along with the GNU MP Library. If not, see http://www.gnu.org/licenses/.
+
+include(`../config.m4')
+
+
+C K7: 17.0 cycles/limb.
+
+
+C mp_limb_t mpn_mod_1 (mp_srcptr src, mp_size_t size, mp_limb_t divisor);
+C mp_limb_t mpn_mod_1c (mp_srcptr src, mp_size_t size, mp_limb_t divisor,
+C mp_limb_t carry);
+C mp_limb_t mpn_preinv_mod_1 (mp_srcptr src, mp_size_t size, mp_limb_t divisor,
+C mp_limb_t inverse);
+C
+C The code here is the same as mpn_divrem_1, but with the quotient
+C discarded. See mpn/x86/k7/mmx/divrem_1.c for some comments.
+
+
+dnl MUL_THRESHOLD is the size at which the multiply by inverse method is
+dnl used, rather than plain "divl"s. Minimum value 2.
+dnl
+dnl The inverse takes about 50 cycles to calculate, but after that the
+dnl multiply is 17 c/l versus division at 41 c/l.
+dnl
+dnl Using mul or div is about the same speed at 3 limbs, so the threshold
+dnl is set to 4 to get the smaller div code used at 3.
+
+deflit(MUL_THRESHOLD, 4)
+
+
+defframe(PARAM_INVERSE,16) dnl mpn_preinv_mod_1
+defframe(PARAM_CARRY, 16) dnl mpn_mod_1c
+defframe(PARAM_DIVISOR,12)
+defframe(PARAM_SIZE, 8)
+defframe(PARAM_SRC, 4)
+
+defframe(SAVE_EBX, -4)
+defframe(SAVE_ESI, -8)
+defframe(SAVE_EDI, -12)
+defframe(SAVE_EBP, -16)
+
+defframe(VAR_NORM, -20)
+defframe(VAR_INVERSE, -24)
+defframe(VAR_SRC_STOP,-28)
+
+deflit(STACK_SPACE, 28)
+
+ TEXT
+
+ ALIGN(32)
+PROLOGUE(mpn_preinv_mod_1)
+deflit(`FRAME',0)
+ movl PARAM_SRC, %ecx
+ movl PARAM_SIZE, %eax
+ subl $STACK_SPACE, %esp FRAME_subl_esp(STACK_SPACE)
+
+ movl %ebp, SAVE_EBP
+ movl PARAM_DIVISOR, %ebp
+
+ movl %edi, SAVE_EDI
+ movl PARAM_INVERSE, %edx
+
+ movl %esi, SAVE_ESI
+ movl -4(%ecx,%eax,4), %edi C src high limb
+ leal -16(%ecx,%eax,4), %ecx C &src[size-4]
+
+ movl %ebx, SAVE_EBX
+ movl PARAM_INVERSE, %edx
+
+ movl $0, VAR_NORM C l==0
+
+ movl %edi, %esi
+ subl %ebp, %edi C high-divisor
+
+ cmovc( %esi, %edi) C restore if underflow
+ decl %eax
+ jz L(done_edi) C size==1, high-divisor only
+
+ movl 8(%ecx), %esi C src second high limb
+ movl %edx, VAR_INVERSE
+
+ movl $32, %ebx C 32-l
+ decl %eax
+ jz L(inverse_one_left) C size==2, one divide
+
+ movd %ebx, %mm7 C 32-l
+ decl %eax
+ jz L(inverse_two_left) C size==3, two divides
+
+ jmp L(inverse_top) C size>=4
+
+
+L(done_edi):
+ movl SAVE_ESI, %esi
+ movl SAVE_EBP, %ebp
+ movl %edi, %eax
+
+ movl SAVE_EDI, %edi
+ addl $STACK_SPACE, %esp
+
+ ret
+
+EPILOGUE()
+
+
+ ALIGN(32)
+PROLOGUE(mpn_mod_1c)
+deflit(`FRAME',0)
+ movl PARAM_CARRY, %edx
+ movl PARAM_SIZE, %ecx
+ subl $STACK_SPACE, %esp
+deflit(`FRAME',STACK_SPACE)
+
+ movl %ebp, SAVE_EBP
+ movl PARAM_DIVISOR, %ebp
+
+ movl %esi, SAVE_ESI
+ movl PARAM_SRC, %esi
+ jmp L(start_1c)
+
+EPILOGUE()
+
+
+ ALIGN(32)
+PROLOGUE(mpn_mod_1)
+deflit(`FRAME',0)
+
+ movl PARAM_SIZE, %ecx
+ movl $0, %edx C initial carry (if can't skip a div)
+ subl $STACK_SPACE, %esp
+deflit(`FRAME',STACK_SPACE)
+
+ movl %esi, SAVE_ESI
+ movl PARAM_SRC, %esi
+
+ movl %ebp, SAVE_EBP
+ movl PARAM_DIVISOR, %ebp
+
+ orl %ecx, %ecx
+ jz L(divide_done)
+
+ movl -4(%esi,%ecx,4), %eax C src high limb
+
+ cmpl %ebp, %eax C carry flag if high<divisor
+
+ cmovc( %eax, %edx) C src high limb as initial carry
+ sbbl $0, %ecx C size-1 to skip one div
+ jz L(divide_done)
+
+
+ ALIGN(16)
+L(start_1c):
+ C eax
+ C ebx
+ C ecx size
+ C edx carry
+ C esi src
+ C edi
+ C ebp divisor
+
+ cmpl $MUL_THRESHOLD, %ecx
+ jae L(mul_by_inverse)
+
+
+
+C With a MUL_THRESHOLD of 4, this "loop" only ever does 1 to 3 iterations,
+C but it's already fast and compact, and there's nothing to gain by
+C expanding it out.
+C
+C Using PARAM_DIVISOR in the divl is a couple of cycles faster than %ebp.
+
+ orl %ecx, %ecx
+ jz L(divide_done)
+
+
+L(divide_top):
+ C eax scratch (quotient)
+ C ebx
+ C ecx counter, limbs, decrementing
+ C edx scratch (remainder)
+ C esi src
+ C edi
+ C ebp
+
+ movl -4(%esi,%ecx,4), %eax
+
+ divl PARAM_DIVISOR
+
+ decl %ecx
+ jnz L(divide_top)
+
+
+L(divide_done):
+ movl SAVE_ESI, %esi
+ movl SAVE_EBP, %ebp
+ addl $STACK_SPACE, %esp
+
+ movl %edx, %eax
+
+ ret
+
+
+
+C -----------------------------------------------------------------------------
+
+L(mul_by_inverse):
+ C eax
+ C ebx
+ C ecx size
+ C edx carry
+ C esi src
+ C edi
+ C ebp divisor
+
+ bsrl %ebp, %eax C 31-l
+
+ movl %ebx, SAVE_EBX
+ movl %ecx, %ebx C size
+
+ movl %edi, SAVE_EDI
+ movl $31, %ecx
+
+ movl %edx, %edi C carry
+ movl $-1, %edx
+
+ C
+
+ xorl %eax, %ecx C l
+ incl %eax C 32-l
+
+ shll %cl, %ebp C d normalized
+ movl %ecx, VAR_NORM
+
+ movd %eax, %mm7 C 32-l
+
+ movl $-1, %eax
+ subl %ebp, %edx C (b-d)-1 so edx:eax = b*(b-d)-1
+
+ divl %ebp C floor (b*(b-d)-1) / d
+
+ C
+
+ movl %eax, VAR_INVERSE
+ leal -12(%esi,%ebx,4), %eax C &src[size-3]
+
+ movl 8(%eax), %esi C src high limb
+ movl 4(%eax), %edx C src second highest limb
+
+ shldl( %cl, %esi, %edi) C n2 = carry,high << l
+
+ shldl( %cl, %edx, %esi) C n10 = high,second << l
+
+ movl %eax, %ecx C &src[size-3]
+
+
+ifelse(MUL_THRESHOLD,2,`
+ cmpl $2, %ebx
+ je L(inverse_two_left)
+')
+
+
+C The dependent chain here is the same as in mpn_divrem_1, but a few
+C instructions are saved by not needing to store the quotient limbs.
+C Unfortunately this doesn't get the code down to the theoretical 16 c/l.
+C
+C There's four dummy instructions in the loop, all of which are necessary
+C for the claimed 17 c/l. It's a 1 to 3 cycle slowdown if any are removed,
+C or changed from load to store or vice versa. They're not completely
+C random, since they correspond to what mpn_divrem_1 has, but there's no
+C obvious reason why they're necessary. Presumably they induce something
+C good in the out of order execution, perhaps through some load/store
+C ordering and/or decoding effects.
+C
+C The q1==0xFFFFFFFF case is handled here the same as in mpn_divrem_1. On
+C on special data that comes out as q1==0xFFFFFFFF always, the loop runs at
+C about 13.5 c/l.
+
+ ALIGN(32)
+L(inverse_top):
+ C eax scratch
+ C ebx scratch (nadj, q1)
+ C ecx src pointer, decrementing
+ C edx scratch
+ C esi n10
+ C edi n2
+ C ebp divisor
+ C
+ C mm0 scratch (src qword)
+ C mm7 rshift for normalization
+
+ cmpl $0x80000000, %esi C n1 as 0=c, 1=nc
+ movl %edi, %eax C n2
+ movl PARAM_SIZE, %ebx C dummy
+
+ leal (%ebp,%esi), %ebx
+ cmovc( %esi, %ebx) C nadj = n10 + (-n1 & d), ignoring overflow
+ sbbl $-1, %eax C n2+n1
+
+ mull VAR_INVERSE C m*(n2+n1)
+
+ movq (%ecx), %mm0 C next src limb and the one below it
+ subl $4, %ecx
+
+ movl %ecx, PARAM_SIZE C dummy
+
+ C
+
+ addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
+ leal 1(%edi), %ebx C n2+1
+ movl %ebp, %eax C d
+
+ C
+
+ adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
+ jz L(q1_ff)
+ nop C dummy
+
+ mull %ebx C (q1+1)*d
+
+ psrlq %mm7, %mm0
+ leal (%ecx), %ecx C dummy
+
+ C
+
+ C
+
+ subl %eax, %esi C low n - (q1+1)*d
+ movl PARAM_SRC, %eax
+
+ C
+
+ sbbl %edx, %edi C high n - (q1+1)*d, 0 or -1
+ movl %esi, %edi C remainder -> n2
+ leal (%ebp,%esi), %edx
+
+ movd %mm0, %esi
+
+ cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
+ cmpl %eax, %ecx
+ jae L(inverse_top)
+
+
+L(inverse_loop_done):
+
+
+C -----------------------------------------------------------------------------
+
+L(inverse_two_left):
+ C eax scratch
+ C ebx scratch (nadj, q1)
+ C ecx &src[-1]
+ C edx scratch
+ C esi n10
+ C edi n2
+ C ebp divisor
+ C
+ C mm0 scratch (src dword)
+ C mm7 rshift
+
+ cmpl $0x80000000, %esi C n1 as 0=c, 1=nc
+ movl %edi, %eax C n2
+
+ leal (%ebp,%esi), %ebx
+ cmovc( %esi, %ebx) C nadj = n10 + (-n1 & d), ignoring overflow
+ sbbl $-1, %eax C n2+n1
+
+ mull VAR_INVERSE C m*(n2+n1)
+
+ movd 4(%ecx), %mm0 C src low limb
+
+ C
+
+ C
+
+ addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
+ leal 1(%edi), %ebx C n2+1
+ movl %ebp, %eax C d
+
+ adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
+
+ sbbl $0, %ebx
+
+ mull %ebx C (q1+1)*d
+
+ psllq $32, %mm0
+
+ psrlq %mm7, %mm0
+
+ C
+
+ subl %eax, %esi
+
+ C
+
+ sbbl %edx, %edi C n - (q1+1)*d
+ movl %esi, %edi C remainder -> n2
+ leal (%ebp,%esi), %edx
+
+ movd %mm0, %esi
+
+ cmovc( %edx, %edi) C n - q1*d if underflow from using q1+1
+
+
+L(inverse_one_left):
+ C eax scratch
+ C ebx scratch (nadj, q1)
+ C ecx
+ C edx scratch
+ C esi n10
+ C edi n2
+ C ebp divisor
+ C
+ C mm0 src limb, shifted
+ C mm7 rshift
+
+ cmpl $0x80000000, %esi C n1 as 0=c, 1=nc
+ movl %edi, %eax C n2
+
+ leal (%ebp,%esi), %ebx
+ cmovc( %esi, %ebx) C nadj = n10 + (-n1 & d), ignoring overflow
+ sbbl $-1, %eax C n2+n1
+
+ mull VAR_INVERSE C m*(n2+n1)
+
+ movl VAR_NORM, %ecx C for final denorm
+
+ C
+
+ C
+
+ addl %ebx, %eax C m*(n2+n1) + nadj, low giving carry flag
+ leal 1(%edi), %ebx C n2+1
+ movl %ebp, %eax C d
+
+ C
+
+ adcl %edx, %ebx C 1 + high(n2<<32 + m*(n2+n1) + nadj) = q1+1
+
+ sbbl $0, %ebx
+
+ mull %ebx C (q1+1)*d
+
+ movl SAVE_EBX, %ebx
+
+ C
+
+ C
+
+ subl %eax, %esi
+
+ movl %esi, %eax C remainder
+ movl SAVE_ESI, %esi
+
+ sbbl %edx, %edi C n - (q1+1)*d
+ leal (%ebp,%eax), %edx
+ movl SAVE_EBP, %ebp
+
+ cmovc( %edx, %eax) C n - q1*d if underflow from using q1+1
+ movl SAVE_EDI, %edi
+
+ shrl %cl, %eax C denorm remainder
+ addl $STACK_SPACE, %esp
+ emms
+
+ ret
+
+
+C -----------------------------------------------------------------------------
+C
+C Special case for q1=0xFFFFFFFF, giving q=0xFFFFFFFF meaning the low dword
+C of q*d is simply -d and the remainder n-q*d = n10+d
+
+L(q1_ff):
+ C eax (divisor)
+ C ebx (q1+1 == 0)
+ C ecx src pointer
+ C edx
+ C esi n10
+ C edi (n2)
+ C ebp divisor
+
+ movl PARAM_SRC, %edx
+ leal (%ebp,%esi), %edi C n-q*d remainder -> next n2
+ psrlq %mm7, %mm0
+
+ movd %mm0, %esi C next n10
+
+ cmpl %edx, %ecx
+ jae L(inverse_top)
+ jmp L(inverse_loop_done)
+
+EPILOGUE()
projects / msp430-gcc.git / blobdiff