270 lines
7.0 KiB
ArmAsm
270 lines
7.0 KiB
ArmAsm
;; Copyright (C) 2001-2017 Free Software Foundation, Inc.
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;;
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;; This file is part of GCC.
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;;
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;; GCC is free software; you can redistribute it and/or modify it under
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;; the terms of the GNU General Public License as published by the Free
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;; Software Foundation; either version 3, or (at your option) any later
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;; version.
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;;
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;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY
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;; WARRANTY; without even the implied warranty of MERCHANTABILITY or
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;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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;; for more details.
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;;
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;; Under Section 7 of GPL version 3, you are granted additional
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;; permissions described in the GCC Runtime Library Exception, version
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;; 3.1, as published by the Free Software Foundation.
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;;
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;; You should have received a copy of the GNU General Public License and
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;; a copy of the GCC Runtime Library Exception along with this program;
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;; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
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;; <http://www.gnu.org/licenses/>.
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;;
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;; This code used to be expanded through interesting expansions in
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;; the machine description, compiled from this code:
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;;
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;; #ifdef L_mulsi3
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;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__));
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;;
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;; /* This must be compiled with the -mexpand-mul flag, to synthesize the
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;; multiplication from the mstep instructions. The check for
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;; smaller-size multiplication pays off in the order of .5-10%;
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;; estimated median 1%, depending on application.
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;; FIXME: It can be further optimized if we go to assembler code, as
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;; gcc 2.7.2 adds a few unnecessary instructions and does not put the
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;; basic blocks in optimal order. */
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;; long
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;; __Mul (unsigned long a, unsigned long b)
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;; {
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;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
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;; /* In case other code is compiled without -march=v10, they will
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;; contain calls to __Mul, regardless of flags at link-time. The
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;; "else"-code below will work, but is unnecessarily slow. This
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;; sometimes cuts a few minutes off from simulation time by just
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;; returning a "mulu.d". */
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;; return a * b;
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;; #else
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;; unsigned long min;
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;;
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;; /* Get minimum via the bound insn. */
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;; min = a < b ? a : b;
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;;
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;; /* Can we omit computation of the high part? */
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;; if (min > 65535)
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;; /* No. Perform full multiplication. */
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;; return a * b;
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;; else
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;; {
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;; /* Check if both operands are within 16 bits. */
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;; unsigned long max;
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;;
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;; /* Get maximum, by knowing the minimum.
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;; This will partition a and b into max and min.
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;; This is not currently something GCC understands,
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;; so do this trick by asm. */
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;; __asm__ ("xor %1,%0\n\txor %2,%0"
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;; : "=r" (max)
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;; : "r" (b), "r" (a), "0" (min));
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;;
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;; if (max > 65535)
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;; /* Make GCC understand that only the low part of "min" will be
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;; used. */
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;; return max * (unsigned short) min;
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;; else
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;; /* Only the low parts of both operands are necessary. */
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;; return ((unsigned short) max) * (unsigned short) min;
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;; }
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;; #endif /* not __CRIS_arch_version >= 10 */
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;; }
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;; #endif /* L_mulsi3 */
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;;
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;; That approach was abandoned since the caveats outweighted the
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;; benefits. The expand-multiplication machinery is also removed, so you
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;; can't do this anymore.
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;;
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;; For doubters of there being any benefits, some where: insensitivity to:
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;; - ABI changes (mostly for experimentation)
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;; - assembler syntax differences (mostly debug format).
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;; - insn scheduling issues.
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;; Most ABI experiments will presumably happen with arches with mul insns,
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;; so that argument doesn't really hold anymore, and it's unlikely there
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;; being new arch variants needing insn scheduling and not having mul
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;; insns.
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;; ELF and a.out have different syntax for local labels: the "wrong"
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;; one may not be omitted from the object.
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#undef L
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#ifdef __AOUT__
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# define L(x) x
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#else
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# define L(x) .x
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#endif
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.global ___Mul
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.type ___Mul,@function
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___Mul:
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#if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
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;; Can't have the mulu.d last on a cache-line (in the delay-slot of the
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;; "ret"), due to hardware bug. See documentation for -mmul-bug-workaround.
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;; Not worthwhile to conditionalize here.
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.p2alignw 2,0x050f
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mulu.d $r11,$r10
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ret
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nop
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#else
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;; See if we can avoid multiplying some of the parts, knowing
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;; they're zero.
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move.d $r11,$r9
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bound.d $r10,$r9
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cmpu.w 65535,$r9
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bls L(L3)
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move.d $r10,$r12
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;; Nope, have to do all the parts of a 32-bit multiplication.
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;; See head comment in optabs.c:expand_doubleword_mult.
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move.d $r10,$r13
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movu.w $r11,$r9 ; ab*cd = (a*d + b*c)<<16 + b*d
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lslq 16,$r13
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mstep $r9,$r13 ; d*b
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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mstep $r9,$r13
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clear.w $r10
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test.d $r10
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mstep $r9,$r10 ; d*a
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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mstep $r9,$r10
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movu.w $r12,$r12
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clear.w $r11
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move.d $r11,$r9 ; Doubles as a "test.d" preparing for the mstep.
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mstep $r12,$r9 ; b*c
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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mstep $r12,$r9
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add.w $r9,$r10
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lslq 16,$r10
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ret
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add.d $r13,$r10
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L(L3):
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;; Form the maximum in $r10, by knowing the minimum, $r9.
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;; (We don't know which one of $r10 or $r11 it is.)
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;; Check if the largest operand is still just 16 bits.
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xor $r9,$r10
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xor $r11,$r10
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cmpu.w 65535,$r10
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bls L(L5)
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movu.w $r9,$r13
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;; We have ab*cd = (a*c)<<32 + (a*d + b*c)<<16 + b*d, but c==0
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;; so we only need (a*d)<<16 + b*d with d = $r13, ab = $r10.
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;; We drop the upper part of (a*d)<<16 as we're only doing a
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;; 32-bit-result multiplication.
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move.d $r10,$r9
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lslq 16,$r9
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mstep $r13,$r9 ; b*d
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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mstep $r13,$r9
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clear.w $r10
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test.d $r10
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mstep $r13,$r10 ; a*d
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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lslq 16,$r10
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ret
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add.d $r9,$r10
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L(L5):
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;; We have ab*cd = (a*c)<<32 + (a*d + b*c)<<16 + b*d, but a and c==0
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;; so b*d (with b=$r13, a=$r10) it is.
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lslq 16,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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mstep $r13,$r10
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ret
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mstep $r13,$r10
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#endif
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L(Lfe1):
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.size ___Mul,L(Lfe1)-___Mul
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