powerpc64le: Optimized memmove for POWER10

This patch was initially based on the __memmove_power7 with some ideas
from strncpy implementation for Power 9.

Improvements from __memmove_power7:

1. Use lxvl/stxvl for alignment code.

   The code for Power 7 uses branches when the input is not naturally
   aligned to the width of a vector. The new implementation uses
   lxvl/stxvl instead which reduces pressure on GPRs. It also allows
   the removal of branch instructions, implicitly removing branch stalls
   and mispredictions.

2. Use of lxv/stxv and lxvl/stxvl pair is safe to use on Cache Inhibited
   memory.

   On Power 10 vector load and stores are safe to use on CI memory for
   addresses unaligned to 16B. This code takes advantage of this to
   do unaligned loads.

   The unaligned loads don't have a significant performance impact by
   themselves. However doing so decreases register pressure on GPRs
   and interdependence stalls on load/store pairs. This also improved
   readability as there are now less code paths for different alignments.
   Finally this reduces the overall code size.

3. Improved performance.

   This version runs on average about 30% better than memmove_power7
   for lengths  larger than 8KB. For input lengths shorter than 8KB
   the improvement is smaller, it has on average about 17% better
   performance.

   This version has a degradation of about 50% for input lengths
   in the 0 to 31 bytes range when dest is unaligned.

Reviewed-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>

diff --git a/sysdeps/powerpc/powerpc64/le/power10/memmove.S b/sysdeps/powerpc/powerpc64/le/power10/memmove.S
new file mode 100644 (file)
index 0000000..7dfd57e
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/le/power10/memmove.S
@@ -0,0 +1,320 @@
+/* Optimized memmove implementation for POWER10.
+   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] memmove (void *dest [r3], const void *src [r4], size_t len [r5])
+
+   This optimization checks if 'src' and 'dst' overlap.  If they do not
+   or 'src' is ahead of 'dest' then it copies forward.
+   Otherwise, an optimized backward copy is used.  */
+
+#ifndef MEMMOVE
+# define MEMMOVE memmove
+#endif
+       .machine power9
+ENTRY_TOCLESS (MEMMOVE, 5)
+       CALL_MCOUNT 3
+
+L(_memmove):
+       .p2align 5
+       /* Check if there is overlap, if so it will branch to backward copy.  */
+       subf    r9,r4,r3
+       cmpld   cr7,r9,r5
+       blt     cr7,L(memmove_bwd)
+
+       /* Fast path for length shorter than 16 bytes.  */
+       sldi    r7,r5,56
+       lxvl    32+v2,r4,r7
+       stxvl   32+v2,r3,r7
+       subic.  r8,r5,16
+       blelr
+
+       /* For shorter lengths aligning the dest address to 16 bytes either
+          decreases performance or is irrelevant.  I'm making use of this
+          comparison to skip the alignment in.  */
+       cmpldi  cr6,r5,256
+       bge     cr6,L(ge_256)
+       /* Account for the first 16-byte copy.  */
+       addi    r4,r4,16
+       addi    r11,r3,16       /* use r11 to keep dest address on r3.  */
+       subi    r5,r5,16
+       b       L(loop_head)
+
+       .p2align 5
+L(ge_256):
+       /* Account for the first copy <= 16 bytes.  This is necessary for
+          memmove because at this point the src address can be in front of the
+          dest address.  */
+       clrldi  r9,r5,56
+       li      r8,16
+       cmpldi  r9,16
+       iselgt  r9,r8,r9
+       add     r4,r4,r9
+       add     r11,r3,r9       /* use r11 to keep dest address on r3.  */
+       sub     r5,r5,r9
+
+       /* Align dest to 16 bytes.  */
+       neg     r7,r3
+       clrldi. r9,r7,60
+       beq     L(loop_head)
+
+       .p2align 5
+       sldi    r6,r9,56
+       lxvl    32+v0,r4,r6
+       stxvl   32+v0,r11,r6
+       sub     r5,r5,r9
+       add     r4,r4,r9
+       add     r11,r11,r9
+
+L(loop_head):
+       cmpldi  r5,63
+       ble     L(final_64)
+
+       srdi.   r7,r5,7
+       beq     L(loop_tail)
+
+       mtctr   r7
+
+/* Main loop that copies 128 bytes each iteration.  */
+       .p2align 5
+L(loop):
+       addi    r9,r4,64
+       addi    r10,r11,64
+
+       lxv     32+v0,0(r4)
+       lxv     32+v1,16(r4)
+       lxv     32+v2,32(r4)
+       lxv     32+v3,48(r4)
+
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+
+       addi    r4,r4,128
+       addi    r11,r11,128
+
+       lxv     32+v4,0(r9)
+       lxv     32+v5,16(r9)
+       lxv     32+v6,32(r9)
+       lxv     32+v7,48(r9)
+
+       stxv    32+v4,0(r10)
+       stxv    32+v5,16(r10)
+       stxv    32+v6,32(r10)
+       stxv    32+v7,48(r10)
+
+       bdnz    L(loop)
+       clrldi. r5,r5,57
+       beqlr
+
+/* Copy 64 bytes.  */
+       .p2align 5
+L(loop_tail):
+       cmpldi  cr5,r5,63
+       ble     cr5,L(final_64)
+
+       lxv     32+v0,0(r4)
+       lxv     32+v1,16(r4)
+       lxv     32+v2,32(r4)
+       lxv     32+v3,48(r4)
+
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+
+       addi    r4,r4,64
+       addi    r11,r11,64
+       subi    r5,r5,64
+
+/* Copies the last 1-63 bytes.  */
+       .p2align 5
+L(final_64):
+       /* r8 holds the number of bytes that will be copied with lxv/stxv.  */
+       clrrdi. r8,r5,4
+       beq     L(tail1)
+
+       cmpldi  cr5,r5,32
+       lxv     32+v0,0(r4)
+       blt     cr5,L(tail2)
+
+       cmpldi  cr6,r5,48
+       lxv     32+v1,16(r4)
+       blt     cr6,L(tail3)
+
+       .p2align 5
+       lxv     32+v2,32(r4)
+       stxv    32+v2,32(r11)
+L(tail3):
+       stxv    32+v1,16(r11)
+L(tail2):
+       stxv    32+v0,0(r11)
+       sub     r5,r5,r8
+       add     r4,r4,r8
+       add     r11,r11,r8
+       .p2align 5
+L(tail1):
+       sldi    r6,r5,56
+       lxvl    v4,r4,r6
+       stxvl   v4,r11,r6
+       blr
+
+/* If dest and src overlap, we should copy backwards.  */
+L(memmove_bwd):
+       add     r11,r3,r5
+       add     r4,r4,r5
+
+       /* Optimization for length smaller than 16 bytes.  */
+       cmpldi  cr5,r5,15
+       ble     cr5,L(tail1_bwd)
+
+       /* For shorter lengths the alignment either slows down or is irrelevant.
+          The forward copy uses a already need 256 comparison for that.  Here
+          it's using 128 as it will reduce code and improve readability.  */
+       cmpldi  cr7,r5,128
+       blt     cr7,L(bwd_loop_tail)
+
+       /* Align dest address to 16 bytes.  */
+       .p2align 5
+       clrldi. r9,r11,60
+       beq     L(bwd_loop_head)
+       sub     r4,r4,r9
+       sub     r11,r11,r9
+       lxv     32+v0,0(r4)
+       sldi    r6,r9,56
+       stxvl   32+v0,r11,r6
+       sub     r5,r5,r9
+
+L(bwd_loop_head):
+       srdi.   r7,r5,7
+       beq     L(bwd_loop_tail)
+
+       mtctr   r7
+
+/* Main loop that copies 128 bytes every iteration.  */
+       .p2align 5
+L(bwd_loop):
+       addi    r9,r4,-64
+       addi    r10,r11,-64
+
+       lxv     32+v0,-16(r4)
+       lxv     32+v1,-32(r4)
+       lxv     32+v2,-48(r4)
+       lxv     32+v3,-64(r4)
+
+       stxv    32+v0,-16(r11)
+       stxv    32+v1,-32(r11)
+       stxv    32+v2,-48(r11)
+       stxv    32+v3,-64(r11)
+
+       addi    r4,r4,-128
+       addi    r11,r11,-128
+
+       lxv     32+v0,-16(r9)
+       lxv     32+v1,-32(r9)
+       lxv     32+v2,-48(r9)
+       lxv     32+v3,-64(r9)
+
+       stxv    32+v0,-16(r10)
+       stxv    32+v1,-32(r10)
+       stxv    32+v2,-48(r10)
+       stxv    32+v3,-64(r10)
+
+       bdnz    L(bwd_loop)
+       clrldi. r5,r5,57
+       beqlr
+
+/* Copy 64 bytes.  */
+       .p2align 5
+L(bwd_loop_tail):
+       cmpldi  cr5,r5,63
+       ble     cr5,L(bwd_final_64)
+
+       addi    r4,r4,-64
+       addi    r11,r11,-64
+
+       lxv     32+v0,0(r4)
+       lxv     32+v1,16(r4)
+       lxv     32+v2,32(r4)
+       lxv     32+v3,48(r4)
+
+       stxv    32+v0,0(r11)
+       stxv    32+v1,16(r11)
+       stxv    32+v2,32(r11)
+       stxv    32+v3,48(r11)
+
+       subi    r5,r5,64
+
+/* Copies the last 1-63 bytes.  */
+       .p2align 5
+L(bwd_final_64):
+       /* r8 holds the number of bytes that will be copied with lxv/stxv.  */
+       clrrdi. r8,r5,4
+       beq     L(tail1_bwd)
+
+       cmpldi  cr5,r5,32
+       lxv     32+v2,-16(r4)
+       blt     cr5,L(tail2_bwd)
+
+       cmpldi  cr6,r5,48
+       lxv     32+v1,-32(r4)
+       blt     cr6,L(tail3_bwd)
+
+       .p2align 5
+       lxv     32+v0,-48(r4)
+       stxv    32+v0,-48(r11)
+L(tail3_bwd):
+       stxv    32+v1,-32(r11)
+L(tail2_bwd):
+       stxv    32+v2,-16(r11)
+       sub     r4,r4,r5
+       sub     r11,r11,r5
+       sub     r5,r5,r8
+       sldi    r6,r5,56
+       lxvl    v4,r4,r6
+       stxvl   v4,r11,r6
+       blr
+
+/* Copy last 16 bytes.  */
+       .p2align 5
+L(tail1_bwd):
+       sub     r4,r4,r5
+       sub     r11,r11,r5
+       sldi    r6,r5,56
+       lxvl    v4,r4,r6
+       stxvl   v4,r11,r6
+       blr
+
+END_GEN_TB (MEMMOVE,TB_TOCLESS)
+libc_hidden_builtin_def (memmove)
+
+/* void bcopy(const void *src [r3], void *dest [r4], size_t n [r5])
+   Implemented in this file to avoid linker create a stub function call
+   in the branch to '_memmove'.  */
+ENTRY_TOCLESS (__bcopy)
+       mr      r6,r3
+       mr      r3,r4
+       mr      r4,r6
+       b       L(_memmove)
+END (__bcopy)
+#ifndef __bcopy
+weak_alias (__bcopy, bcopy)
+#endif

diff --git a/sysdeps/powerpc/powerpc64/multiarch/Makefile b/sysdeps/powerpc/powerpc64/multiarch/Makefile
index 8aa46a3..a82219c 100644 (file)
--- a/sysdeps/powerpc/powerpc64/multiarch/Makefile
+++ b/sysdeps/powerpc/powerpc64/multiarch/Makefile
@@ -32,7 +32,8 @@ sysdep_routines += memcpy-power8-cached memcpy-power7 memcpy-a2 memcpy-power6 \
                   strncase-power8
 
 ifneq (,$(filter %le,$(config-machine)))
-sysdep_routines += strcmp-power9 strncmp-power9 strcpy-power9 stpcpy-power9 \
+sysdep_routines += memmove-power10 \
+                  strcmp-power9 strncmp-power9 strcpy-power9 stpcpy-power9 \
                   rawmemchr-power9 strlen-power9 strncpy-power9 stpncpy-power9 \
                   strlen-power10
 endif

diff --git a/sysdeps/powerpc/powerpc64/multiarch/bcopy.c b/sysdeps/powerpc/powerpc64/multiarch/bcopy.c
index 04f3432..2840b17 100644 (file)
--- a/sysdeps/powerpc/powerpc64/multiarch/bcopy.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/bcopy.c
@@ -22,8 +22,17 @@
 extern __typeof (bcopy) __bcopy_ppc attribute_hidden;
 /* __bcopy_power7 symbol is implemented at memmove-power7.S  */
 extern __typeof (bcopy) __bcopy_power7 attribute_hidden;
+#ifdef __LITTLE_ENDIAN__
+extern __typeof (bcopy) __bcopy_power10 attribute_hidden;
+#endif
 
 libc_ifunc (bcopy,
+#ifdef __LITTLE_ENDIAN__
+            hwcap2 & (PPC_FEATURE2_ARCH_3_1 |
+                      PPC_FEATURE2_HAS_ISEL)
+            && (hwcap & PPC_FEATURE_HAS_VSX)
+            ? __bcopy_power10 :
+#endif
             (hwcap & PPC_FEATURE_HAS_VSX)
             ? __bcopy_power7
             : __bcopy_ppc);

diff --git a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
index 1a69936..d00bcc8 100644 (file)
--- a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
@@ -67,6 +67,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   /* Support sysdeps/powerpc/powerpc64/multiarch/memmove.c.  */
   IFUNC_IMPL (i, name, memmove,
+#ifdef __LITTLE_ENDIAN__
+             IFUNC_IMPL_ADD (array, i, memmove,
+                             hwcap2 & (PPC_FEATURE2_ARCH_3_1 |
+                                       PPC_FEATURE2_HAS_ISEL)
+                             && (hwcap & PPC_FEATURE_HAS_VSX),
+                             __memmove_power10)
+#endif
              IFUNC_IMPL_ADD (array, i, memmove, hwcap & PPC_FEATURE_HAS_VSX,
                              __memmove_power7)
              IFUNC_IMPL_ADD (array, i, memmove, 1, __memmove_ppc))
@@ -186,6 +193,13 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   /* Support sysdeps/powerpc/powerpc64/multiarch/bcopy.c.  */
   IFUNC_IMPL (i, name, bcopy,
+#ifdef __LITTLE_ENDIAN__
+             IFUNC_IMPL_ADD (array, i, bcopy,
+                             hwcap2 & (PPC_FEATURE2_ARCH_3_1 |
+                                       PPC_FEATURE2_HAS_ISEL)
+                             && (hwcap & PPC_FEATURE_HAS_VSX),
+                             __bcopy_power10)
+#endif
              IFUNC_IMPL_ADD (array, i, bcopy, hwcap & PPC_FEATURE_HAS_VSX,
                              __bcopy_power7)
              IFUNC_IMPL_ADD (array, i, bcopy, 1, __bcopy_ppc))

diff --git a/sysdeps/powerpc/powerpc64/multiarch/memmove-power10.S b/sysdeps/powerpc/powerpc64/multiarch/memmove-power10.S
new file mode 100644 (file)
index 0000000..171b329
--- /dev/null
+++ b/sysdeps/powerpc/powerpc64/multiarch/memmove-power10.S
@@ -0,0 +1,27 @@
+/* Optimized memmove implementation for POWER10.
+   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 MEMMOVE __memmove_power10
+
+#undef libc_hidden_builtin_def
+#define libc_hidden_builtin_def(name)
+
+#undef __bcopy
+#define __bcopy __bcopy_power10
+
+#include <sysdeps/powerpc/powerpc64/le/power10/memmove.S>

diff --git a/sysdeps/powerpc/powerpc64/multiarch/memmove-power7.S b/sysdeps/powerpc/powerpc64/multiarch/memmove-power7.S
index d66da58..27b196d 100644 (file)
--- a/sysdeps/powerpc/powerpc64/multiarch/memmove-power7.S
+++ b/sysdeps/powerpc/powerpc64/multiarch/memmove-power7.S
@@ -21,7 +21,7 @@
 #undef libc_hidden_builtin_def
 #define libc_hidden_builtin_def(name)
 
-#undef bcopy
-#define bcopy __bcopy_power7
+#undef __bcopy
+#define __bcopy __bcopy_power7
 
 #include <sysdeps/powerpc/powerpc64/power7/memmove.S>

diff --git a/sysdeps/powerpc/powerpc64/multiarch/memmove.c b/sysdeps/powerpc/powerpc64/multiarch/memmove.c
index 9bec61a..420c2f2 100644 (file)
--- a/sysdeps/powerpc/powerpc64/multiarch/memmove.c
+++ b/sysdeps/powerpc/powerpc64/multiarch/memmove.c
@@ -28,14 +28,22 @@
 # include "init-arch.h"
 
 extern __typeof (__redirect_memmove) __libc_memmove;
-
 extern __typeof (__redirect_memmove) __memmove_ppc attribute_hidden;
 extern __typeof (__redirect_memmove) __memmove_power7 attribute_hidden;
+#ifdef __LITTLE_ENDIAN__
+extern __typeof (__redirect_memmove) __memmove_power10 attribute_hidden;
+#endif
 
 libc_ifunc (__libc_memmove,
-            (hwcap & PPC_FEATURE_HAS_VSX)
-            ? __memmove_power7
-            : __memmove_ppc);
+#ifdef __LITTLE_ENDIAN__
+            hwcap2 & (PPC_FEATURE2_ARCH_3_1 |
+                      PPC_FEATURE2_HAS_ISEL)
+            && (hwcap & PPC_FEATURE_HAS_VSX)
+            ? __memmove_power10 :
+#endif
+                    (hwcap & PPC_FEATURE_HAS_VSX)
+                    ? __memmove_power7
+                    : __memmove_ppc);
 
 #undef memmove
 strong_alias (__libc_memmove, memmove);

diff --git a/sysdeps/powerpc/powerpc64/power7/memmove.S b/sysdeps/powerpc/powerpc64/power7/memmove.S
index 8366145..f61949d 100644 (file)
--- a/sysdeps/powerpc/powerpc64/power7/memmove.S
+++ b/sysdeps/powerpc/powerpc64/power7/memmove.S
@@ -832,4 +832,6 @@ ENTRY_TOCLESS (__bcopy)
        mr      r4,r6
        b       L(_memmove)
 END (__bcopy)
+#ifndef __bcopy
 weak_alias (__bcopy, bcopy)
+#endif