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+/* 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)