commit 23fdf8178cce3c2ec320dd5eca8b544245bcaef0
Author: Raoni Fassina Firmino <raoni@linux.ibm.com>
Date: Fri Apr 30 18:12:08 2021 -0300
powerpc64le: Optimize memset for POWER10
This implementation is based on __memset_power8 and integrates a lot
of suggestions from Anton Blanchard.
The biggest difference is that it makes extensive use of stxvl to
alignment and tail code to avoid branches and small stores. It has
three main execution paths:
a) "Short lengths" for lengths up to 64 bytes, avoiding as many
branches as possible.
b) "General case" for larger lengths, it has an alignment section
using stxvl to avoid branches, a 128 bytes loop and then a tail
code, again using stxvl with few branches.
c) "Zeroing cache blocks" for lengths from 256 bytes upwards and set
value being zero. It is mostly the __memset_power8 code but the
alignment phase was simplified because, at this point, address is
already 16-bytes aligned and also changed to use vector stores.
The tail code was also simplified to reuse the general case tail.
All unaligned stores use stxvl instructions that do not generate
alignment interrupts on POWER10, making it safe to use on
caching-inhibited memory.
On average, this implementation provides something around 30%
improvement when compared to __memset_power8.
Reviewed-by: Matheus Castanho <msc@linux.ibm.com>
Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
diff --git a/sysdeps/powerpc/powerpc64/le/power10/memset.S b/sysdeps/powerpc/powerpc64/le/power10/memset.S
new file mode 100644
index 0000000000000000..6b8e2cfdaf25fd30
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/le/power10/memset.S
@@ -0,0 +1,256 @@
+/* Optimized memset implementation for POWER10 LE.
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ 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
+ <https://www.gnu.org/licenses/>. */
+
+#include <sysdep.h>
+
+/* void * [r3] memset (void *s [r3], int c [r4], size_t n [r5]));
+ Returns 's'. */
+
+#ifndef MEMSET
+# define MEMSET memset
+#endif
+
+ .machine power9
+ENTRY_TOCLESS (MEMSET, 5)
+ CALL_MCOUNT 3
+
+L(_memset):
+ /* Assume memset of zero length is uncommon, and just let it go
+ through the small path below. */
+ cmpldi r5,64
+
+ /* Replicate byte to quad word. */
+ mtvsrd v0+32,r4
+ vspltb v0,v0,7
+
+ li r7,16
+ sldi r8,r7,56
+
+ bgt L(large)
+
+ /* For short lengths we want to avoid as many branches as possible.
+ We use store VSX vector with length instructions to do this.
+ It takes advantage of the fact that if the length passed to stxvl
+ is zero nothing is done, effectively a no-op. */
+ sldi r5,r5,56
+
+ addi r10,r3,16
+
+ sub. r11,r5,r8
+ isellt r11,0,r11 /* Saturate the subtraction to zero. */
+
+ stxvl v0+32,r3,r5
+ stxvl v0+32,r10,r11
+
+ addi r9,r3,32
+ addi r10,r3,48
+
+ sub. r11,r11,r8
+ isellt r11,0,r11
+
+ sub. r5,r11,r8
+ isellt r5,0,r5
+
+ stxvl v0+32,r9,r11
+ stxvl v0+32,r10,r5
+
+ blr
+
+ .balign 16
+L(large):
+ mr r6,r3 /* Don't modify r3 since we need to return it. */
+
+ /* Get dest 16B aligned. */
+ neg r0,r3
+ clrldi. r7,r0,(64-4)
+ beq L(aligned)
+ rldic r9,r0,56,4 /* (~X & 0xf)<<56 "clrlsldi r9,r0,64-4,56". */
+
+ stxvl v0+32,r6,r9 /* Store up to 15B until aligned address. */
+
+ add r6,r6,r7
+ sub r5,r5,r7
+
+ /* Go to tail if there is less than 64B left after alignment. */
+ cmpldi r5,64
+ blt L(tail_64)
+
+ .balign 16
+L(aligned):
+ /* Go to tail if there is less than 128B left after alignment. */
+ srdi. r0,r5,7
+ beq L(tail_128)
+
+ /* If c == 0 && n >= 256 use dcbz to zero out full cache blocks. */
+ cmpldi cr5,r5,255
+ cmpldi cr6,r4,0
+ crand 27,26,21
+ bt 27,L(dcbz)
+
+ mtctr r0
+
+ .balign 32
+L(loop):
+ stxv v0+32,0(r6)
+ stxv v0+32,16(r6)
+ stxv v0+32,32(r6)
+ stxv v0+32,48(r6)
+ stxv v0+32,64(r6)
+ stxv v0+32,80(r6)
+ stxv v0+32,96(r6)
+ stxv v0+32,112(r6)
+ addi r6,r6,128
+ bdnz L(loop)
+
+ .balign 16
+L(tail):
+ /* 127B or less left, finish the tail or return. */
+ andi. r5,r5,127
+ beqlr
+
+ cmpldi r5,64
+ blt L(tail_64)
+
+ .balign 16
+L(tail_128):
+ /* Stores a minimum of 64B and up to 128B and return. */
+ stxv v0+32,0(r6)
+ stxv v0+32,16(r6)
+ stxv v0+32,32(r6)
+ stxv v0+32,48(r6)
+ addi r6,r6,64
+ andi. r5,r5,63
+ beqlr
+
+ .balign 16
+L(tail_64):
+ /* Stores up to 64B and return. */
+ sldi r5,r5,56
+
+ addi r10,r6,16
+
+ sub. r11,r5,r8
+ isellt r11,0,r11
+
+ stxvl v0+32,r6,r5
+ stxvl v0+32,r10,r11
+
+ sub. r11,r11,r8
+ blelr
+
+ addi r9,r6,32
+ addi r10,r6,48
+
+ isellt r11,0,r11
+
+ sub. r5,r11,r8
+ isellt r5,0,r5
+
+ stxvl v0+32,r9,r11
+ stxvl v0+32,r10,r5
+
+ blr
+
+ .balign 16
+L(dcbz):
+ /* Special case when value is 0 and we have a long length to deal
+ with. Use dcbz to zero out a full cacheline of 128 bytes at a time.
+ Before using dcbz though, we need to get the destination 128-byte
+ aligned. */
+ neg r0,r6
+ clrldi. r0,r0,(64-7)
+ beq L(dcbz_aligned)
+
+ sub r5,r5,r0
+ mtocrf 0x2,r0 /* copying bits 57..59 to cr6. The ones for sizes 64,
+ 32 and 16 which need to be checked. */
+
+ /* Write 16-128 bytes until DST is aligned to 128 bytes. */
+64: bf 25,32f
+ stxv v0+32,0(r6)
+ stxv v0+32,16(r6)
+ stxv v0+32,32(r6)
+ stxv v0+32,48(r6)
+ addi r6,r6,64
+
+32: bf 26,16f
+ stxv v0+32,0(r6)
+ stxv v0+32,16(r6)
+ addi r6,r6,32
+
+16: bf 27,L(dcbz_aligned)
+ stxv v0+32,0(r6)
+ addi r6,r6,16
+
+ .balign 16
+L(dcbz_aligned):
+ /* Setup dcbz unroll offsets and count numbers. */
+ srdi. r0,r5,9
+ li r9,128
+ beq L(bcdz_tail)
+ li r10,256
+ li r11,384
+ mtctr r0
+
+ .balign 16
+L(dcbz_loop):
+ /* Sets 512 bytes to zero in each iteration, the loop unrolling shows
+ a throughput boost for large sizes (2048 bytes or higher). */
+ dcbz 0,r6
+ dcbz r9,r6
+ dcbz r10,r6
+ dcbz r11,r6
+ addi r6,r6,512
+ bdnz L(dcbz_loop)
+
+ andi. r5,r5,511
+ beqlr
+
+ .balign 16
+L(bcdz_tail):
+ /* We have 1-511 bytes remaining. */
+ srdi. r0,r5,7
+ beq L(tail)
+
+ mtocrf 0x1,r0
+
+256: bf 30,128f
+ dcbz 0,r6
+ dcbz r9,r6
+ addi r6,r6,256
+
+128: bf 31,L(tail)
+ dcbz 0,r6
+ addi r6,r6,128
+
+ b L(tail)
+
+END_GEN_TB (MEMSET,TB_TOCLESS)
+libc_hidden_builtin_def (memset)
+
+/* Copied from bzero.S to prevent the linker from inserting a stub
+ between bzero and memset. */
+ENTRY_TOCLESS (__bzero)
+ CALL_MCOUNT 2
+ mr r5,r4
+ li r4,0
+ b L(_memset)
+END (__bzero)
+#ifndef __bzero
+weak_alias (__bzero, bzero)
+#endif
diff --git a/sysdeps/powerpc/powerpc64/multiarch/Makefile b/sysdeps/powerpc/powerpc64/multiarch/Makefile
index 2e3c8f2e8a81cda4..1d517698429e1230 100644
--- a/sysdeps/powerpc/powerpc64/multiarch/Makefile
+++ b/sysdeps/powerpc/powerpc64/multiarch/Makefile
@@ -32,7 +32,7 @@ sysdep_routines += memcpy-power8-cached memcpy-power7 memcpy-a2 memcpy-power6 \
strncase-power8
ifneq (,$(filter %le,$(config-machine)))
-sysdep_routines += memcpy-power10 memmove-power10 \
+sysdep_routines += memcpy-power10 memmove-power10 memset-power10 \
strcmp-power9 strncmp-power9 strcpy-power9 stpcpy-power9 \
rawmemchr-power9 strlen-power9 strncpy-power9 stpncpy-power9 \
strlen-power10
diff --git a/sysdeps/powerpc/powerpc64/multiarch/bzero.c b/sysdeps/powerpc/powerpc64/multiarch/bzero.c
index f8cb05bea8a3505b..4ce98e324d12a31e 100644
--- a/sysdeps/powerpc/powerpc64/multiarch/bzero.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/bzero.c
@@ -27,8 +27,16 @@ extern __typeof (bzero) __bzero_power4 attribute_hidden;
extern __typeof (bzero) __bzero_power6 attribute_hidden;
extern __typeof (bzero) __bzero_power7 attribute_hidden;
extern __typeof (bzero) __bzero_power8 attribute_hidden;
+# ifdef __LITTLE_ENDIAN__
+extern __typeof (bzero) __bzero_power10 attribute_hidden;
+# endif
libc_ifunc (__bzero,
+# ifdef __LITTLE_ENDIAN__
+ (hwcap2 & (PPC_FEATURE2_ARCH_3_1 | PPC_FEATURE2_HAS_ISEL)
+ && hwcap & PPC_FEATURE_HAS_VSX)
+ ? __bzero_power10 :
+# endif
(hwcap2 & PPC_FEATURE2_ARCH_2_07)
? __bzero_power8 :
(hwcap & PPC_FEATURE_HAS_VSX)
diff --git a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
index 9d5a14e480c02171..11532f77d4d03b2a 100644
--- a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
@@ -86,6 +86,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/powerpc/powerpc64/multiarch/memset.c. */
IFUNC_IMPL (i, name, memset,
+#ifdef __LITTLE_ENDIAN__
+ IFUNC_IMPL_ADD (array, i, memset,
+ hwcap2 & (PPC_FEATURE2_ARCH_3_1 |
+ PPC_FEATURE2_HAS_ISEL)
+ && hwcap & PPC_FEATURE_HAS_VSX,
+ __memset_power10)
+#endif
IFUNC_IMPL_ADD (array, i, memset, hwcap2 & PPC_FEATURE2_ARCH_2_07,
__memset_power8)
IFUNC_IMPL_ADD (array, i, memset, hwcap & PPC_FEATURE_HAS_VSX,
@@ -187,6 +194,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
/* Support sysdeps/powerpc/powerpc64/multiarch/bzero.c. */
IFUNC_IMPL (i, name, bzero,
+#ifdef __LITTLE_ENDIAN__
+ IFUNC_IMPL_ADD (array, i, bzero,
+ hwcap2 & (PPC_FEATURE2_ARCH_3_1 |
+ PPC_FEATURE2_HAS_ISEL)
+ && hwcap & PPC_FEATURE_HAS_VSX,
+ __bzero_power10)
+#endif
IFUNC_IMPL_ADD (array, i, bzero, hwcap2 & PPC_FEATURE2_ARCH_2_07,
__bzero_power8)
IFUNC_IMPL_ADD (array, i, bzero, hwcap & PPC_FEATURE_HAS_VSX,
diff --git a/sysdeps/powerpc/powerpc64/multiarch/memset-power10.S b/sysdeps/powerpc/powerpc64/multiarch/memset-power10.S
new file mode 100644
index 0000000000000000..548e99789735296c
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/multiarch/memset-power10.S
@@ -0,0 +1,27 @@
+/* Optimized memset implementation for POWER10 LE.
+ Copyright (C) 2021 Free Software Foundation, Inc.
+ 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
+ <https://www.gnu.org/licenses/>. */
+
+#define MEMSET __memset_power10
+
+#undef libc_hidden_builtin_def
+#define libc_hidden_builtin_def(name)
+
+#undef __bzero
+#define __bzero __bzero_power10
+
+#include <sysdeps/powerpc/powerpc64/le/power10/memset.S>
diff --git a/sysdeps/powerpc/powerpc64/multiarch/memset.c b/sysdeps/powerpc/powerpc64/multiarch/memset.c
index 1a7c46fecf78ab1f..4c97622c7d7eb8aa 100644
--- a/sysdeps/powerpc/powerpc64/multiarch/memset.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/memset.c
@@ -33,10 +33,18 @@ extern __typeof (__redirect_memset) __memset_power4 attribute_hidden;
extern __typeof (__redirect_memset) __memset_power6 attribute_hidden;
extern __typeof (__redirect_memset) __memset_power7 attribute_hidden;
extern __typeof (__redirect_memset) __memset_power8 attribute_hidden;
+# ifdef __LITTLE_ENDIAN__
+extern __typeof (__redirect_memset) __memset_power10 attribute_hidden;
+# endif
/* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
ifunc symbol properly. */
libc_ifunc (__libc_memset,
+# ifdef __LITTLE_ENDIAN__
+ (hwcap2 & (PPC_FEATURE2_ARCH_3_1 | PPC_FEATURE2_HAS_ISEL)
+ && hwcap & PPC_FEATURE_HAS_VSX)
+ ? __memset_power10 :
+# endif
(hwcap2 & PPC_FEATURE2_ARCH_2_07)
? __memset_power8 :
(hwcap & PPC_FEATURE_HAS_VSX)