libgcc/config/cris/mulsi3.S - gcc - Git at Google

 ;; Copyright (C) 2001-2021 Free Software Foundation, Inc.
 ;;
 ;; This file is part of GCC.
 ;;
 ;; GCC is free software; you can redistribute it and/or modify it under
 ;; the terms of the GNU General Public License as published by the Free
 ;; Software Foundation; either version 3, or (at your option) any later
 ;; version.
 ;;
 ;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY
 ;; WARRANTY; without even the implied warranty of MERCHANTABILITY or
 ;; FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 ;; for more details.
 ;;
 ;; Under Section 7 of GPL version 3, you are granted additional
 ;; permissions described in the GCC Runtime Library Exception, version
 ;; 3.1, as published by the Free Software Foundation.
 ;;
 ;; You should have received a copy of the GNU General Public License and
 ;; a copy of the GCC Runtime Library Exception along with this program;
 ;; see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
 ;; <http://www.gnu.org/licenses/>.
 ;;
 ;; This code used to be expanded through interesting expansions in
 ;; the machine description, compiled from this code:
 ;;
 ;; #ifdef L_mulsi3
 ;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__));
 ;;
 ;; /* This must be compiled with the -mexpand-mul flag, to synthesize the
 ;;    multiplication from the mstep instructions.  The check for
 ;;    smaller-size multiplication pays off in the order of .5-10%;
 ;;    estimated median 1%, depending on application.
 ;;     FIXME: It can be further optimized if we go to assembler code, as
 ;;    gcc 2.7.2 adds a few unnecessary instructions and does not put the
 ;;    basic blocks in optimal order.  */
 ;; long
 ;; __Mul (unsigned long a, unsigned long b)
 ;; {
 ;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
 ;;   /* In case other code is compiled without -march=v10, they will
 ;; 	contain calls to __Mul, regardless of flags at link-time.  The
 ;; 	"else"-code below will work, but is unnecessarily slow.  This
 ;; 	sometimes cuts a few minutes off from simulation time by just
 ;; 	returning a "mulu.d".  */
 ;;   return a * b;
 ;; #else
 ;;   unsigned long min;
 ;;
 ;;   /* Get minimum via the bound insn.  */
 ;;   min = a < b ? a : b;
 ;;
 ;;   /* Can we omit computation of the high part?	*/
 ;;   if (min > 65535)
 ;;     /* No.  Perform full multiplication.  */
 ;;     return a * b;
 ;;   else
 ;;     {
 ;; 	 /* Check if both operands are within 16 bits.  */
 ;; 	 unsigned long max;
 ;;
 ;; 	 /* Get maximum, by knowing the minimum.
 ;; 	    This will partition a and b into max and min.
 ;; 	    This is not currently something GCC understands,
 ;; 	    so do this trick by asm.  */
 ;; 	 __asm__ ("xor %1,%0\n\txor %2,%0"
 ;; 		  : "=r" (max)
 ;; 		  :  "r" (b), "r" (a), "0" (min));
 ;;
 ;;     if (max > 65535)
 ;; 	 /* Make GCC understand that only the low part of "min" will be
 ;; 	    used.  */
 ;; 	 return max * (unsigned short) min;
 ;;     else
 ;; 	 /* Only the low parts of both operands are necessary.  */
 ;; 	 return ((unsigned short) max) * (unsigned short) min;
 ;;     }
 ;; #endif /* not __CRIS_arch_version >= 10 */
 ;; }
 ;; #endif /* L_mulsi3 */
 ;;
 ;; That approach was abandoned since the caveats outweighted the
 ;; benefits.  The expand-multiplication machinery is also removed, so you
 ;; can't do this anymore.
 ;;
 ;; For doubters of there being any benefits, some where: insensitivity to:
 ;; - ABI changes (mostly for experimentation)
 ;; - assembler syntax differences (mostly debug format).
 ;; - insn scheduling issues.
 ;; Most ABI experiments will presumably happen with arches with mul insns,
 ;; so that argument doesn't really hold anymore, and it's unlikely there
 ;; being new arch variants needing insn scheduling and not having mul
 ;; insns.

 ;; ELF and a.out have different syntax for local labels: the "wrong"
 ;; one may not be omitted from the object.
 #undef L
 #ifdef __AOUT__
 # define L(x) x
 #else
 # define L(x) .x
 #endif

 	.global ___Mul
 	.type	___Mul,@function
 ___Mul:
 #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
 ;; Can't have the mulu.d last on a cache-line (in the delay-slot of the
 ;; "ret"), due to hardware bug.  See documentation for -mmul-bug-workaround.
 ;; Not worthwhile to conditionalize here.
 	.p2alignw 2,0x050f
 	mulu.d $r11,$r10
 	ret
 	nop
 #else
 ;; See if we can avoid multiplying some of the parts, knowing
 ;; they're zero.

 	move.d $r11,$r9
 	bound.d $r10,$r9
 	cmpu.w 65535,$r9
 	bls L(L3)
 	move.d $r10,$r12

 ;; Nope, have to do all the parts of a 32-bit multiplication.
 ;; See head comment in optabs.c:expand_doubleword_mult.

 	move.d $r10,$r13
 	movu.w $r11,$r9 ; ab*cd = (a*d + b*c)<<16 + b*d
 	lslq 16,$r13
 	mstep $r9,$r13	; d*b
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	mstep $r9,$r13
 	clear.w $r10
 	test.d $r10
 	mstep $r9,$r10	; d*a
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	mstep $r9,$r10
 	movu.w $r12,$r12
 	clear.w $r11
 	move.d $r11,$r9 ; Doubles as a "test.d" preparing for the mstep.
 	mstep $r12,$r9	; b*c
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	mstep $r12,$r9
 	add.w $r9,$r10
 	lslq 16,$r10
 	ret
 	add.d $r13,$r10

 L(L3):
 ;; Form the maximum in $r10, by knowing the minimum, $r9.
 ;; (We don't know which one of $r10 or $r11 it is.)
 ;; Check if the largest operand is still just 16 bits.

 	xor $r9,$r10
 	xor $r11,$r10
 	cmpu.w 65535,$r10
 	bls L(L5)
 	movu.w $r9,$r13

 ;; We have ab*cd = (a*c)<<32 + (a*d + b*c)<<16 + b*d, but c==0
 ;; so we only need (a*d)<<16 + b*d with d = $r13, ab = $r10.
 ;; We drop the upper part of (a*d)<<16 as we're only doing a
 ;; 32-bit-result multiplication.

 	move.d $r10,$r9
 	lslq 16,$r9
 	mstep $r13,$r9	; b*d
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	mstep $r13,$r9
 	clear.w $r10
 	test.d $r10
 	mstep $r13,$r10	; a*d
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	lslq 16,$r10
 	ret
 	add.d $r9,$r10

 L(L5):
 ;; We have ab*cd = (a*c)<<32 + (a*d + b*c)<<16 + b*d, but a and c==0
 ;; so b*d (with b=$r13, a=$r10) it is.

 	lslq 16,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	mstep $r13,$r10
 	ret
 	mstep $r13,$r10
 #endif
 L(Lfe1):
 	.size	___Mul,L(Lfe1)-___Mul
	;; Copyright (C) 2001-2021 Free Software Foundation, Inc.
	;;
	;; This file is part of GCC.
	;;
	;; GCC is free software; you can redistribute it and/or modify it under
	;; the terms of the GNU General Public License as published by the Free
	;; Software Foundation; either version 3, or (at your option) any later
	;; version.
	;;
	;; GCC is distributed in the hope that it will be useful, but WITHOUT ANY
	;; WARRANTY; without even the implied warranty of MERCHANTABILITY or
	;; FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
	;; for more details.
	;;
	;; Under Section 7 of GPL version 3, you are granted additional
	;; permissions described in the GCC Runtime Library Exception, version
	;; 3.1, as published by the Free Software Foundation.
	;;
	;; You should have received a copy of the GNU General Public License and
	;; a copy of the GCC Runtime Library Exception along with this program;
	;; see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
	;; <http://www.gnu.org/licenses/>.
	;;
	;; This code used to be expanded through interesting expansions in
	;; the machine description, compiled from this code:
	;;
	;; #ifdef L_mulsi3
	;; long __Mul (unsigned long a, unsigned long b) __attribute__ ((__const__));
	;;
	;; /* This must be compiled with the -mexpand-mul flag, to synthesize the
	;; multiplication from the mstep instructions. The check for
	;; smaller-size multiplication pays off in the order of .5-10%;
	;; estimated median 1%, depending on application.
	;; FIXME: It can be further optimized if we go to assembler code, as
	;; gcc 2.7.2 adds a few unnecessary instructions and does not put the
	;; basic blocks in optimal order. */
	;; long
	;; __Mul (unsigned long a, unsigned long b)
	;; {
	;; #if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
	;; /* In case other code is compiled without -march=v10, they will
	;; contain calls to __Mul, regardless of flags at link-time. The
	;; "else"-code below will work, but is unnecessarily slow. This
	;; sometimes cuts a few minutes off from simulation time by just
	;; returning a "mulu.d". */
	;; return a * b;
	;; #else
	;; unsigned long min;
	;;
	;; /* Get minimum via the bound insn. */
	;; min = a < b ? a : b;
	;;
	;; /* Can we omit computation of the high part? */
	;; if (min > 65535)
	;; /* No. Perform full multiplication. */
	;; return a * b;
	;; else
	;; {
	;; /* Check if both operands are within 16 bits. */
	;; unsigned long max;
	;;
	;; /* Get maximum, by knowing the minimum.
	;; This will partition a and b into max and min.
	;; This is not currently something GCC understands,
	;; so do this trick by asm. */
	;; __asm__ ("xor %1,%0\n\txor %2,%0"
	;; : "=r" (max)
	;; : "r" (b), "r" (a), "0" (min));
	;;
	;; if (max > 65535)
	;; /* Make GCC understand that only the low part of "min" will be
	;; used. */
	;; return max * (unsigned short) min;
	;; else
	;; /* Only the low parts of both operands are necessary. */
	;; return ((unsigned short) max) * (unsigned short) min;
	;; }
	;; #endif /* not __CRIS_arch_version >= 10 */
	;; }
	;; #endif /* L_mulsi3 */
	;;
	;; That approach was abandoned since the caveats outweighted the
	;; benefits. The expand-multiplication machinery is also removed, so you
	;; can't do this anymore.
	;;
	;; For doubters of there being any benefits, some where: insensitivity to:
	;; - ABI changes (mostly for experimentation)
	;; - assembler syntax differences (mostly debug format).
	;; - insn scheduling issues.
	;; Most ABI experiments will presumably happen with arches with mul insns,
	;; so that argument doesn't really hold anymore, and it's unlikely there
	;; being new arch variants needing insn scheduling and not having mul
	;; insns.

	;; ELF and a.out have different syntax for local labels: the "wrong"
	;; one may not be omitted from the object.
	#undef L
	#ifdef __AOUT__
	# define L(x) x
	#else
	# define L(x) .x
	#endif

	.global ___Mul
	.type ___Mul,@function
	___Mul:
	#if defined (__CRIS_arch_version) && __CRIS_arch_version >= 10
	;; Can't have the mulu.d last on a cache-line (in the delay-slot of the
	;; "ret"), due to hardware bug. See documentation for -mmul-bug-workaround.
	;; Not worthwhile to conditionalize here.
	.p2alignw 2,0x050f
	mulu.d $r11,$r10
	ret
	nop
	#else
	;; See if we can avoid multiplying some of the parts, knowing
	;; they're zero.

	move.d $r11,$r9
	bound.d $r10,$r9
	cmpu.w 65535,$r9
	bls L(L3)
	move.d $r10,$r12

	;; Nope, have to do all the parts of a 32-bit multiplication.
	;; See head comment in optabs.c:expand_doubleword_mult.

	move.d $r10,$r13
	movu.w $r11,$r9 ; abcd = (ad + bc)<<16 + bd
	lslq 16,$r13
	mstep $r9,$r13 ; d*b
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	mstep $r9,$r13
	clear.w $r10
	test.d $r10
	mstep $r9,$r10 ; d*a
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	mstep $r9,$r10
	movu.w $r12,$r12
	clear.w $r11
	move.d $r11,$r9 ; Doubles as a "test.d" preparing for the mstep.
	mstep $r12,$r9 ; b*c
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	mstep $r12,$r9
	add.w $r9,$r10
	lslq 16,$r10
	ret
	add.d $r13,$r10

	L(L3):
	;; Form the maximum in $r10, by knowing the minimum, $r9.
	;; (We don't know which one of $r10 or $r11 it is.)
	;; Check if the largest operand is still just 16 bits.

	xor $r9,$r10
	xor $r11,$r10
	cmpu.w 65535,$r10
	bls L(L5)
	movu.w $r9,$r13

	;; We have abcd = (ac)<<32 + (ad + bc)<<16 + b*d, but c==0
	;; so we only need (ad)<<16 + bd with d = $r13, ab = $r10.
	;; We drop the upper part of (a*d)<<16 as we're only doing a
	;; 32-bit-result multiplication.

	move.d $r10,$r9
	lslq 16,$r9
	mstep $r13,$r9 ; b*d
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	mstep $r13,$r9
	clear.w $r10
	test.d $r10
	mstep $r13,$r10 ; a*d
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	lslq 16,$r10
	ret
	add.d $r9,$r10

	L(L5):
	;; We have abcd = (ac)<<32 + (ad + bc)<<16 + b*d, but a and c==0
	;; so b*d (with b=$r13, a=$r10) it is.

	lslq 16,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	mstep $r13,$r10
	ret
	mstep $r13,$r10
	#endif
	L(Lfe1):
	.size ___Mul,L(Lfe1)-___Mul