google3/third_party/grte/v4_src/glibc-2.19/ports/sysdeps/alpha/alphaev6/memset.S - GRTEv4 - Git at Google

 /* Copyright (C) 2000-2014 Free Software Foundation, Inc.
    Contributed by Richard Henderson (rth@tamu.edu)
    EV6 optimized by Rick Gorton <rick.gorton@alpha-processor.com>.
    This file is part of the GNU C Library.

    The GNU C Library is free software; you can redistribute it and/or
    modify it under the terms of the GNU Lesser General Public
    License as published by the Free Software Foundation; either
    version 2.1 of the License, or (at your option) any later version.

    The GNU C Library 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
    Lesser General Public License for more details.

    You should have received a copy of the GNU Lesser General Public
    License along with the GNU C Library.  If not, see
    <http://www.gnu.org/licenses/>.  */

 #include <sysdep.h>

 	.arch ev6
 	.set noat
 	.set noreorder

 ENTRY(memset)
 #ifdef PROF
 	ldgp	gp, 0(pv)
 	lda	AT, _mcount
 	jsr	AT, (AT), _mcount
 	.prologue 1
 #else
 	.prologue 0
 #endif

 	/*
 	 * Serious stalling happens.  The only way to mitigate this is to
 	 * undertake a major re-write to interleave the constant materialization
 	 * with other parts of the fall-through code.  This is important, even
 	 * though it makes maintenance tougher.
 	 * Do this later.
 	 */
 	and	$17, 255, $1	# E : 00000000000000ch
 	insbl	$17, 1, $2	# U : 000000000000ch00
 	mov	$16, $0		# E : return value
 	ble	$18, $end	# U : zero length requested?

 	addq	$18, $16, $6	# E : max address to write to
 	or	$1, $2, $17	# E : 000000000000chch
 	insbl	$1, 2, $3	# U : 0000000000ch0000
 	insbl	$1, 3, $4	# U : 00000000ch000000

 	or	$3, $4, $3	# E : 00000000chch0000
 	inswl	$17, 4, $5	# U : 0000chch00000000
 	xor	$16, $6, $1	# E : will complete write be within one quadword?
 	inswl	$17, 6, $2	# U : chch000000000000

 	or	$17, $3, $17	# E : 00000000chchchch
 	or	$2, $5, $2	# E : chchchch00000000
 	bic	$1, 7, $1	# E : fit within a single quadword?
 	and	$16, 7, $3	# E : Target addr misalignment

 	or	$17, $2, $17	# E : chchchchchchchch
 	beq	$1, $within_quad # U :
 	nop			# E :
 	beq	$3, $aligned	# U : target is 0mod8

 	/*
 	 * Target address is misaligned, and won't fit within a quadword.
 	 */
 	ldq_u	$4, 0($16)	# L : Fetch first partial
 	mov	$16, $5		# E : Save the address
 	insql	$17, $16, $2	# U : Insert new bytes
 	subq	$3, 8, $3	# E : Invert (for addressing uses)

 	addq	$18, $3, $18	# E : $18 is new count ($3 is negative)
 	mskql	$4, $16, $4	# U : clear relevant parts of the quad
 	subq	$16, $3, $16	# E : $16 is new aligned destination
 	or	$2, $4, $1	# E : Final bytes

 	nop
 	stq_u	$1,0($5)	# L : Store result
 	nop
 	nop

 	.align 4
 $aligned:
 	/*
 	 * We are now guaranteed to be quad aligned, with at least
 	 * one partial quad to write.
 	 */

 	sra	$18, 3, $3	# U : Number of remaining quads to write
 	and	$18, 7, $18	# E : Number of trailing bytes to write
 	mov	$16, $5		# E : Save dest address
 	beq	$3, $no_quad	# U : tail stuff only

 	/*
 	 * It's worth the effort to unroll this and use wh64 if possible.
 	 * At this point, entry values are:
 	 * $16	Current destination address
 	 * $5	A copy of $16
 	 * $6	The max quadword address to write to
 	 * $18	Number trailer bytes
 	 * $3	Number quads to write
 	 */

 	and	$16, 0x3f, $2	# E : Forward work (only useful for unrolled loop)
 	subq	$3, 16, $4	# E : Only try to unroll if > 128 bytes
 	subq	$2, 0x40, $1	# E : bias counter (aligning stuff 0mod64)
 	blt	$4, $loop	# U :

 	/*
 	 * We know we've got at least 16 quads, minimum of one trip
 	 * through unrolled loop.  Do a quad at a time to get us 0mod64
 	 * aligned.
 	 */

 	nop			# E :
 	nop			# E :
 	nop			# E :
 	beq	$1, $bigalign	# U :

 $alignmod64:
 	stq	$17, 0($5)	# L :
 	subq	$3, 1, $3	# E : For consistency later
 	addq	$1, 8, $1	# E : Increment towards zero for alignment
 	addq	$5, 8, $4	# E : Initial wh64 address (filler instruction)

 	nop
 	nop
 	addq	$5, 8, $5	# E : Inc address
 	blt	$1, $alignmod64 # U :

 $bigalign:
 	/*
 	 * $3 - number quads left to go
 	 * $5 - target address (aligned 0mod64)
 	 * $17 - mask of stuff to store
 	 * Scratch registers available: $7, $2, $4, $1
 	 * We know that we'll be taking a minimum of one trip through.
  	 * CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
 	 * Assumes the wh64 needs to be for 2 trips through the loop in the future.
 	 * The wh64 is issued on for the starting destination address for trip +2
 	 * through the loop, and if there are less than two trips left, the target
 	 * address will be for the current trip.
 	 */

 $do_wh64:
 	wh64	($4)		# L1 : memory subsystem write hint
 	subq	$3, 24, $2	# E : For determining future wh64 addresses
 	stq	$17, 0($5)	# L :
 	nop			# E :

 	addq	$5, 128, $4	# E : speculative target of next wh64
 	stq	$17, 8($5)	# L :
 	stq	$17, 16($5)	# L :
 	addq	$5, 64, $7	# E : Fallback address for wh64 (== next trip addr)

 	stq	$17, 24($5)	# L :
 	stq	$17, 32($5)	# L :
 	cmovlt	$2, $7, $4	# E : Latency 2, extra mapping cycle
 	nop

 	stq	$17, 40($5)	# L :
 	stq	$17, 48($5)	# L :
 	subq	$3, 16, $2	# E : Repeat the loop at least once more?
 	nop

 	stq	$17, 56($5)	# L :
 	addq	$5, 64, $5	# E :
 	subq	$3, 8, $3	# E :
 	bge	$2, $do_wh64	# U :

 	nop
 	nop
 	nop
 	beq	$3, $no_quad	# U : Might have finished already

 	.align 4
 	/*
 	 * Simple loop for trailing quadwords, or for small amounts
 	 * of data (where we can't use an unrolled loop and wh64)
 	 */
 $loop:
 	stq	$17, 0($5)	# L :
 	subq	$3, 1, $3	# E : Decrement number quads left
 	addq	$5, 8, $5	# E : Inc address
 	bne	$3, $loop	# U : more?

 $no_quad:
 	/*
 	 * Write 0..7 trailing bytes.
 	 */
 	nop			# E :
 	beq	$18, $end	# U : All done?
 	ldq	$7, 0($5)	# L :
 	mskqh	$7, $6, $2	# U : Mask final quad

 	insqh	$17, $6, $4	# U : New bits
 	or	$2, $4, $1	# E : Put it all together
 	stq	$1, 0($5)	# L : And back to memory
 	ret	$31,($26),1	# L0 :

 $within_quad:
 	ldq_u	$1, 0($16)	# L :
 	insql	$17, $16, $2	# U : New bits
 	mskql	$1, $16, $4	# U : Clear old
 	or	$2, $4, $2	# E : New result

 	mskql	$2, $6, $4	# U :
 	mskqh	$1, $6, $2	# U :
 	or	$2, $4, $1	# E :
 	stq_u	$1, 0($16)	# L :

 $end:
 	nop
 	nop
 	nop
 	ret $31,($26),1		# L0 :

 	END(memset)
 libc_hidden_builtin_def (memset)
	/* Copyright (C) 2000-2014 Free Software Foundation, Inc.
	Contributed by Richard Henderson (rth@tamu.edu)
	EV6 optimized by Rick Gorton <rick.gorton@alpha-processor.com>.
	This file is part of the GNU C Library.

	The GNU C Library is free software; you can redistribute it and/or
	modify it under the terms of the GNU Lesser General Public
	License as published by the Free Software Foundation; either
	version 2.1 of the License, or (at your option) any later version.

	The GNU C Library 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
	Lesser General Public License for more details.

	You should have received a copy of the GNU Lesser General Public
	License along with the GNU C Library. If not, see
	<http://www.gnu.org/licenses/>. */

	#include <sysdep.h>

	.arch ev6
	.set noat
	.set noreorder

	ENTRY(memset)
	#ifdef PROF
	ldgp gp, 0(pv)
	lda AT, _mcount
	jsr AT, (AT), _mcount
	.prologue 1
	#else
	.prologue 0
	#endif

	/*
	* Serious stalling happens. The only way to mitigate this is to
	* undertake a major re-write to interleave the constant materialization
	* with other parts of the fall-through code. This is important, even
	* though it makes maintenance tougher.
	* Do this later.
	*/
	and $17, 255, $1 # E : 00000000000000ch
	insbl $17, 1, $2 # U : 000000000000ch00
	mov $16, $0 # E : return value
	ble $18, $end # U : zero length requested?

	addq $18, $16, $6 # E : max address to write to
	or $1, $2, $17 # E : 000000000000chch
	insbl $1, 2, $3 # U : 0000000000ch0000
	insbl $1, 3, $4 # U : 00000000ch000000

	or $3, $4, $3 # E : 00000000chch0000
	inswl $17, 4, $5 # U : 0000chch00000000
	xor $16, $6, $1 # E : will complete write be within one quadword?
	inswl $17, 6, $2 # U : chch000000000000

	or $17, $3, $17 # E : 00000000chchchch
	or $2, $5, $2 # E : chchchch00000000
	bic $1, 7, $1 # E : fit within a single quadword?
	and $16, 7, $3 # E : Target addr misalignment

	or $17, $2, $17 # E : chchchchchchchch
	beq $1, $within_quad # U :
	nop # E :
	beq $3, $aligned # U : target is 0mod8

	/*
	* Target address is misaligned, and won't fit within a quadword.
	*/
	ldq_u $4, 0($16) # L : Fetch first partial
	mov $16, $5 # E : Save the address
	insql $17, $16, $2 # U : Insert new bytes
	subq $3, 8, $3 # E : Invert (for addressing uses)

	addq $18, $3, $18 # E : $18 is new count ($3 is negative)
	mskql $4, $16, $4 # U : clear relevant parts of the quad
	subq $16, $3, $16 # E : $16 is new aligned destination
	or $2, $4, $1 # E : Final bytes

	nop
	stq_u $1,0($5) # L : Store result
	nop
	nop

	.align 4
	$aligned:
	/*
	* We are now guaranteed to be quad aligned, with at least
	* one partial quad to write.
	*/

	sra $18, 3, $3 # U : Number of remaining quads to write
	and $18, 7, $18 # E : Number of trailing bytes to write
	mov $16, $5 # E : Save dest address
	beq $3, $no_quad # U : tail stuff only

	/*
	* It's worth the effort to unroll this and use wh64 if possible.
	* At this point, entry values are:
	* $16 Current destination address
	* $5 A copy of $16
	* $6 The max quadword address to write to
	* $18 Number trailer bytes
	* $3 Number quads to write
	*/

	and $16, 0x3f, $2 # E : Forward work (only useful for unrolled loop)
	subq $3, 16, $4 # E : Only try to unroll if > 128 bytes
	subq $2, 0x40, $1 # E : bias counter (aligning stuff 0mod64)
	blt $4, $loop # U :

	/*
	* We know we've got at least 16 quads, minimum of one trip
	* through unrolled loop. Do a quad at a time to get us 0mod64
	* aligned.
	*/

	nop # E :
	nop # E :
	nop # E :
	beq $1, $bigalign # U :

	$alignmod64:
	stq $17, 0($5) # L :
	subq $3, 1, $3 # E : For consistency later
	addq $1, 8, $1 # E : Increment towards zero for alignment
	addq $5, 8, $4 # E : Initial wh64 address (filler instruction)

	nop
	nop
	addq $5, 8, $5 # E : Inc address
	blt $1, $alignmod64 # U :

	$bigalign:
	/*
	* $3 - number quads left to go
	* $5 - target address (aligned 0mod64)
	* $17 - mask of stuff to store
	* Scratch registers available: $7, $2, $4, $1
	* We know that we'll be taking a minimum of one trip through.
	* CWG Section 3.7.6: do not expect a sustained store rate of > 1/cycle
	* Assumes the wh64 needs to be for 2 trips through the loop in the future.
	* The wh64 is issued on for the starting destination address for trip +2
	* through the loop, and if there are less than two trips left, the target
	* address will be for the current trip.
	*/

	$do_wh64:
	wh64 ($4) # L1 : memory subsystem write hint
	subq $3, 24, $2 # E : For determining future wh64 addresses
	stq $17, 0($5) # L :
	nop # E :

	addq $5, 128, $4 # E : speculative target of next wh64
	stq $17, 8($5) # L :
	stq $17, 16($5) # L :
	addq $5, 64, $7 # E : Fallback address for wh64 (== next trip addr)

	stq $17, 24($5) # L :
	stq $17, 32($5) # L :
	cmovlt $2, $7, $4 # E : Latency 2, extra mapping cycle
	nop

	stq $17, 40($5) # L :
	stq $17, 48($5) # L :
	subq $3, 16, $2 # E : Repeat the loop at least once more?
	nop

	stq $17, 56($5) # L :
	addq $5, 64, $5 # E :
	subq $3, 8, $3 # E :
	bge $2, $do_wh64 # U :

	nop
	nop
	nop
	beq $3, $no_quad # U : Might have finished already

	.align 4
	/*
	* Simple loop for trailing quadwords, or for small amounts
	* of data (where we can't use an unrolled loop and wh64)
	*/
	$loop:
	stq $17, 0($5) # L :
	subq $3, 1, $3 # E : Decrement number quads left
	addq $5, 8, $5 # E : Inc address
	bne $3, $loop # U : more?

	$no_quad:
	/*
	* Write 0..7 trailing bytes.
	*/
	nop # E :
	beq $18, $end # U : All done?
	ldq $7, 0($5) # L :
	mskqh $7, $6, $2 # U : Mask final quad

	insqh $17, $6, $4 # U : New bits
	or $2, $4, $1 # E : Put it all together
	stq $1, 0($5) # L : And back to memory
	ret $31,($26),1 # L0 :

	$within_quad:
	ldq_u $1, 0($16) # L :
	insql $17, $16, $2 # U : New bits
	mskql $1, $16, $4 # U : Clear old
	or $2, $4, $2 # E : New result

	mskql $2, $6, $4 # U :
	mskqh $1, $6, $2 # U :
	or $2, $4, $1 # E :
	stq_u $1, 0($16) # L :

	$end:
	nop
	nop
	nop
	ret $31,($26),1 # L0 :

	END(memset)
	libc_hidden_builtin_def (memset)