PowerPC: memset optimization for POWER8/PPC64

This patch adds an optimized memset implementation for POWER8.  For
sizes from 0 to 255 bytes, a word/doubleword algorithm similar to
POWER7 optimized one is used.

For size higher than 255 two strategies are used:

1. If the constant is different than 0, the memory is written with
   altivec vector instruction;

2. If constant is 0, dbcz instructions are used.  The loop is unrolled
   to clear 512 byte at time.

Using vector instructions increases throughput considerable, with a
double performance for sizes larger than 1024.  The dcbz loops unrolls
also shows performance improvement, by doubling throughput for sizes
larger than 8192 bytes.

ChangeLog

@@ -1,5 +1,20 @@
 2014-09-10  Adhemerval Zanella  <azanella@linux.vnet.ibm.com>
 
+	* benchtests/bench-memset.c (test_main): Add more test from size
+	from 32 to 512 bytes.
+	* sysdeps/powerpc/powerpc64/multiarch/Makefile [sysdep_routines]:
+	Add POWER8 memset object.
+	* sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c
+	(__libc_ifunc_impl_list): Add POWER8 memset and bzero implementations.
+	* sysdeps/powerpc/powerpc64/multiarch/bzero.c (__bzero): Add POWER8
+	implementation.
+	* sysdeps/powerpc/powerpc64/multiarch/memset.c (__libc_memset):
+	Likewise.
+	* sysdeps/powerpc/powerpc64/multiarch/memset-power8.S: New file:
+	multiarch POWER8 memset optimization.
+	* sysdeps/powerpc/powerpc64/power8/memset.S: New file: optimized
+	POWER8 memset optimization.
+
 	* sysdeps/powerpc/powerpc64/multiarch/Makefile [sysdep_routines]:
 	Remove bzero multiarch objects.
 	* sysdeps/powerpc/powerpc64/multiarch/bzero-power4.S: Remove file.

benchtests/bench-memset.c

@@ -150,6 +150,11 @@ test_main (void)
 	  if (i & (i - 1))
 	    do_test (0, c, i);
 	}
+      for (i = 32; i < 512; i+=32)
+	{
+	  do_test (0, c, i);
+	  do_test (i, c, i);
+	}
       do_test (1, c, 14);
       do_test (3, c, 1024);
       do_test (4, c, 64);

sysdeps/powerpc/powerpc64/multiarch/Makefile

@@ -2,7 +2,7 @@ ifeq ($(subdir),string)
 sysdep_routines += memcpy-power7 memcpy-a2 memcpy-power6 memcpy-cell \
 		   memcpy-power4 memcpy-ppc64 memcmp-power7 memcmp-power4 \
 		   memcmp-ppc64 memset-power7 memset-power6 memset-power4 \
-		   memset-ppc64 \
+		   memset-ppc64 memset-power8 \
 		   mempcpy-power7 mempcpy-ppc64 memchr-power7 memchr-ppc64 \
 		   memrchr-power7 memrchr-ppc64 rawmemchr-power7 \
 		   rawmemchr-ppc64 strlen-power7 strlen-ppc64 strnlen-power7 \

sysdeps/powerpc/powerpc64/multiarch/bzero.c

@@ -26,14 +26,17 @@ extern __typeof (bzero) __bzero_ppc attribute_hidden;
 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;
 
 libc_ifunc (__bzero,
-            (hwcap & PPC_FEATURE_HAS_VSX)
-            ? __bzero_power7 :
-	      (hwcap & PPC_FEATURE_ARCH_2_05)
+            (hwcap2 & PPC_FEATURE2_ARCH_2_07)
+            ? __bzero_power8 :
+	      (hwcap & PPC_FEATURE_HAS_VSX)
+	      ? __bzero_power7 :
+		(hwcap & PPC_FEATURE_ARCH_2_05)
 		? __bzero_power6 :
 		  (hwcap & PPC_FEATURE_POWER4)
-		? __bzero_power4
+		  ? __bzero_power4
             : __bzero_ppc);
 
 weak_alias (__bzero, bzero)

sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c

@@ -34,6 +34,8 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
   size_t i = 0;
 
   unsigned long int hwcap = GLRO(dl_hwcap);
+  unsigned long int hwcap2 = GLRO(dl_hwcap2);
+
   /* hwcap contains only the latest supported ISA, the code checks which is
      and fills the previous supported ones.  */
   if (hwcap & PPC_FEATURE_ARCH_2_06)
@@ -69,6 +71,8 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   /* Support sysdeps/powerpc/powerpc64/multiarch/memset.c.  */
   IFUNC_IMPL (i, name, memset,
+	      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,
 			      __memset_power7)
 	      IFUNC_IMPL_ADD (array, i, memset, hwcap & PPC_FEATURE_ARCH_2_05,
@@ -134,6 +138,8 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,
 
   /* Support sysdeps/powerpc/powerpc64/multiarch/bzero.c.  */
   IFUNC_IMPL (i, name, bzero,
+	      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,
 			      __bzero_power7)
 	      IFUNC_IMPL_ADD (array, i, bzero, hwcap & PPC_FEATURE_ARCH_2_05,

sysdeps/powerpc/powerpc64/multiarch/memset-power8.S

@@ -0,0 +1,43 @@
+/* Optimized memset implementation for PowerPC64/POWER8.
+   Copyright (C) 2014 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
+   <http://www.gnu.org/licenses/>.  */
+
+#include <sysdep.h>
+
+#undef EALIGN
+#define EALIGN(name, alignt, words)				\
+  .section ".text";						\
+  ENTRY_2(__memset_power8)					\
+  .align ALIGNARG(alignt);					\
+  EALIGN_W_##words;						\
+  BODY_LABEL(__memset_power8):					\
+  cfi_startproc;						\
+  LOCALENTRY(__memset_power8)
+
+#undef END_GEN_TB
+#define END_GEN_TB(name, mask)					\
+  cfi_endproc;							\
+  TRACEBACK_MASK(__memset_power8,mask)				\
+  END_2(__memset_power8)
+
+#undef libc_hidden_builtin_def
+#define libc_hidden_builtin_def(name)
+
+#undef __bzero
+#define __bzero __bzero_power8
+
+#include <sysdeps/powerpc/powerpc64/power8/memset.S>

sysdeps/powerpc/powerpc64/multiarch/memset.c

@@ -32,16 +32,19 @@ extern __typeof (__redirect_memset) __memset_ppc attribute_hidden;
 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;
 
 /* Avoid DWARF definition DIE on ifunc symbol so that GDB can handle
    ifunc symbol properly.  */
 libc_ifunc (__libc_memset,
-            (hwcap & PPC_FEATURE_HAS_VSX)
-            ? __memset_power7 :
-	      (hwcap & PPC_FEATURE_ARCH_2_05)
+            (hwcap2 & PPC_FEATURE2_ARCH_2_07)
+            ? __memset_power8 :
+	      (hwcap & PPC_FEATURE_HAS_VSX)
+	      ? __memset_power7 :
+		(hwcap & PPC_FEATURE_ARCH_2_05)
 		? __memset_power6 :
 		  (hwcap & PPC_FEATURE_POWER4)
-		? __memset_power4
+		  ? __memset_power4
             : __memset_ppc);
 
 #undef memset