Blackfin arch: Replace C version of 64 bit multiply with hand optimized assembly
Signed-off-by: Bernd Schmidt <bernds_cb1@t-online.de> Signed-off-by: Bryan Wu <cooloney@kernel.org>
This commit is contained in:
Bernd Schmidt
Bryan Wu
68
arch/blackfin/lib/muldi3.S
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68
arch/blackfin/lib/muldi3.S
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.align 2
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.global ___muldi3;
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.type ___muldi3, STT_FUNC;
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#ifdef CONFIG_ARITHMETIC_OPS_L1
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.section .l1.text
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#else
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.text
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#endif
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/*
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R1:R0 * R3:R2
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= R1.h:R1.l:R0.h:R0.l * R3.h:R3.l:R2.h:R2.l
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[X] = (R1.h * R3.h) * 2^96
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[X] + (R1.h * R3.l + R1.l * R3.h) * 2^80
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[X] + (R1.h * R2.h + R1.l * R3.l + R3.h * R0.h) * 2^64
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[T1] + (R1.h * R2.l + R3.h * R0.l + R1.l * R2.h + R3.l * R0.h) * 2^48
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[T2] + (R1.l * R2.l + R3.l * R0.l + R0.h * R2.h) * 2^32
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[T3] + (R0.l * R2.h + R2.l * R0.h) * 2^16
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[T4] + (R0.l * R2.l)
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We can discard the first three lines marked "X" since we produce
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only a 64 bit result. So, we need ten 16-bit multiplies.
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Individual mul-acc results:
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[E1] = R1.h * R2.l + R3.h * R0.l + R1.l * R2.h + R3.l * R0.h
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[E2] = R1.l * R2.l + R3.l * R0.l + R0.h * R2.h
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[E3] = R0.l * R2.h + R2.l * R0.h
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[E4] = R0.l * R2.l
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We also need to add high parts from lower-level results to higher ones:
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E[n]c = E[n] + (E[n+1]c >> 16), where E4c := E4
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One interesting property is that all parts of the result that depend
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on the sign of the multiplication are discarded. Those would be the
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multiplications involving R1.h and R3.h, but only the top 16 bit of
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the 32 bit result depend on the sign, and since R1.h and R3.h only
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occur in E1, the top half of these results is cut off.
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So, we can just use FU mode for all of the 16-bit multiplies, and
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ignore questions of when to use mixed mode. */
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___muldi3:
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/* [SP] technically is part of the caller's frame, but we can
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use it as scratch space. */
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A0 = R2.H * R1.L, A1 = R2.L * R1.H (FU) || R3 = [SP + 12]; /* E1 */
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A0 += R3.H * R0.L, A1 += R3.L * R0.H (FU) || [SP] = R4; /* E1 */
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A0 += A1; /* E1 */
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R4 = A0.w;
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A0 = R0.l * R3.l (FU); /* E2 */
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A0 += R2.l * R1.l (FU); /* E2 */
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A1 = R2.L * R0.L (FU); /* E4 */
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R3 = A1.w;
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A1 = A1 >> 16; /* E3c */
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A0 += R2.H * R0.H, A1 += R2.L * R0.H (FU); /* E2, E3c */
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A1 += R0.L * R2.H (FU); /* E3c */
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R0 = A1.w;
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A1 = A1 >> 16; /* E2c */
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A0 += A1; /* E2c */
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R1 = A0.w;
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/* low(result) = low(E3c):low(E4) */
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R0 = PACK (R0.l, R3.l);
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/* high(result) = E2c + (E1 << 16) */
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R1.h = R1.h + R4.l (NS) || R4 = [SP];
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RTS;
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.size ___muldi3, .-___muldi3
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@@ -1,99 +0,0 @@
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/*
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* File: arch/blackfin/lib/muldi3.c
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* Based on:
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* Author:
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*
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* Created:
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* Description:
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*
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* Modified:
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* Copyright 2004-2006 Analog Devices Inc.
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*
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* Bugs: Enter bugs at http://blackfin.uclinux.org/
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, see the file COPYING, or write
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* to the Free Software Foundation, Inc.,
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* 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#ifndef SI_TYPE_SIZE
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#define SI_TYPE_SIZE 32
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#endif
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#define __ll_b (1L << (SI_TYPE_SIZE / 2))
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#define __ll_lowpart(t) ((usitype) (t) % __ll_b)
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#define __ll_highpart(t) ((usitype) (t) / __ll_b)
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#define BITS_PER_UNIT 8
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#if !defined(umul_ppmm)
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#define umul_ppmm(w1, w0, u, v) \
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do { \
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usitype __x0, __x1, __x2, __x3; \
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usitype __ul, __vl, __uh, __vh; \
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\
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__ul = __ll_lowpart (u); \
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__uh = __ll_highpart (u); \
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__vl = __ll_lowpart (v); \
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__vh = __ll_highpart (v); \
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\
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__x0 = (usitype) __ul * __vl; \
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__x1 = (usitype) __ul * __vh; \
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__x2 = (usitype) __uh * __vl; \
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__x3 = (usitype) __uh * __vh; \
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\
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__x1 += __ll_highpart (__x0);/* this can't give carry */ \
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__x1 += __x2; /* but this indeed can */ \
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if (__x1 < __x2) /* did we get it? */ \
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__x3 += __ll_b; /* yes, add it in the proper pos. */ \
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\
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(w1) = __x3 + __ll_highpart (__x1); \
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(w0) = __ll_lowpart (__x1) * __ll_b + __ll_lowpart (__x0); \
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} while (0)
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#endif
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#if !defined(__umulsidi3)
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#define __umulsidi3(u, v) \
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({diunion __w; \
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umul_ppmm (__w.s.high, __w.s.low, u, v); \
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__w.ll; })
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#endif
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typedef unsigned int usitype __attribute__ ((mode(SI)));
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typedef int sitype __attribute__ ((mode(SI)));
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typedef int ditype __attribute__ ((mode(DI)));
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typedef int word_type __attribute__ ((mode(__word__)));
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struct distruct {
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sitype low, high;
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};
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typedef union {
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struct distruct s;
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ditype ll;
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} diunion;
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#ifdef CONFIG_ARITHMETIC_OPS_L1
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ditype __muldi3(ditype u, ditype v)__attribute__((l1_text));
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#endif
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ditype __muldi3(ditype u, ditype v)
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{
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diunion w;
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diunion uu, vv;
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uu.ll = u, vv.ll = v;
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w.ll = __umulsidi3(uu.s.low, vv.s.low);
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w.s.high += ((usitype) uu.s.low * (usitype) vv.s.high
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+ (usitype) uu.s.high * (usitype) vv.s.low);
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return w.ll;
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}
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