commit 1a594aa986ffe28657a03baa5c53c0a0e7dc2ecd

Author: Matheus Castanho <msc@linux.ibm.com>

Date:   Tue May 11 17:53:07 2021 -0300

    powerpc: Add optimized rawmemchr for POWER10

    Reuse code for optimized strlen to implement a faster version of rawmemchr.

    This takes advantage of the same benefits provided by the strlen implementation,

    but needs some extra steps. __strlen_power10 code should be unchanged after this

    change.

    rawmemchr returns a pointer to the char found, while strlen returns only the

    length, so we have to take that into account when preparing the return value.

    To quickly check 64B, the loop on __strlen_power10 merges the whole block into

    16B by using unsigned minimum vector operations (vminub) and checks if there are

    any \0 on the resulting vector. The same code is used by rawmemchr if the char c

    is 0. However, this approach does not work when c != 0.  We first need to

    subtract each byte by c, so that the value we are looking for is converted to a

    0, then taking the minimum and checking for nulls works again.

    The new code branches after it has compared ~256 bytes and chooses which of the

    two strategies above will be used in the main loop, based on the char c. This

    extra branch adds some overhead (~5%) for length ~256, but is quickly amortized

    by the faster loop for larger sizes.

    Compared to __rawmemchr_power9, this version is ~20% faster for length < 256.

    Because of the optimized main loop, the improvement becomes ~35% for c != 0

    and ~50% for c = 0 for strings longer than 256.

    Reviewed-by: Lucas A. M. Magalhaes <lamm@linux.ibm.com>

    Reviewed-by: Raphael M Zinsly <rzinsly@linux.ibm.com>

diff --git a/sysdeps/powerpc/powerpc64/le/power10/rawmemchr.S b/sysdeps/powerpc/powerpc64/le/power10/rawmemchr.S

new file mode 100644

index 0000000000000000..5351c2634f6086bf

--- /dev/null

+++ b/sysdeps/powerpc/powerpc64/le/power10/rawmemchr.S

@@ -0,0 +1,22 @@

+/* Optimized rawmemchr 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>

+

+#define USE_AS_RAWMEMCHR 1

+#include <sysdeps/powerpc/powerpc64/le/power10/strlen.S>

diff --git a/sysdeps/powerpc/powerpc64/le/power10/strlen.S b/sysdeps/powerpc/powerpc64/le/power10/strlen.S

index ca7e9eb3d84c9b00..dda5282f1b9a07cf 100644

--- a/sysdeps/powerpc/powerpc64/le/power10/strlen.S

+++ b/sysdeps/powerpc/powerpc64/le/power10/strlen.S

@@ -18,10 +18,50 @@

 #include <sysdep.h>

-#ifndef STRLEN

-# define STRLEN __strlen

-# define DEFINE_STRLEN_HIDDEN_DEF 1

-#endif

+/* To reuse the code for rawmemchr, we have some extra steps compared to the

+   strlen implementation:

+      - Sum the initial value of r3 with the position at which the char was

+        found, to guarantee we return a pointer and not the length.

+      - In the main loop, subtract each byte by the char we are looking for,

+        so we can keep using vminub to quickly check 64B at once.  */

+#ifdef USE_AS_RAWMEMCHR

+# ifndef RAWMEMCHR

+#  define FUNCNAME __rawmemchr

+# else

+#  define FUNCNAME RAWMEMCHR

+# endif

+# define MCOUNT_NARGS 2

+# define VREG_ZERO v20

+# define OFF_START_LOOP 256

+# define RAWMEMCHR_SUBTRACT_VECTORS \

+	vsububm   v4,v4,v18;	    \

+	vsububm   v5,v5,v18;	    \

+	vsububm   v6,v6,v18;	    \

+	vsububm   v7,v7,v18;

+# define TAIL(vreg,increment)	   \

+	vctzlsbb  r4,vreg;	   \

+	addi	  r4,r4,increment; \

+	add	  r3,r5,r4;	   \

+	blr

+

+#else /* strlen */

+

+# ifndef STRLEN

+#  define FUNCNAME __strlen

+#  define DEFINE_STRLEN_HIDDEN_DEF 1

+# else

+#  define FUNCNAME STRLEN

+# endif

+# define MCOUNT_NARGS 1

+# define VREG_ZERO v18

+# define OFF_START_LOOP 192

+# define TAIL(vreg,increment)	   \

+	vctzlsbb  r4,vreg;	   \

+	subf	  r3,r3,r5;	   \

+	addi	  r4,r4,increment; \

+	add	  r3,r3,r4;	   \

+	blr

+#endif /* USE_AS_RAWMEMCHR */

 /* TODO: Replace macros by the actual instructions when minimum binutils becomes

    >= 2.35.  This is used to keep compatibility with older versions.  */

@@ -50,33 +90,41 @@

 	li	  r6,offset;		    \

 	LXVP(v4+32,offset,addr);	    \

 	LXVP(v6+32,offset+32,addr);	    \

+	RAWMEMCHR_SUBTRACT_VECTORS;	    \

 	vminub	  v14,v4,v5;		    \

 	vminub	  v15,v6,v7;		    \

 	vminub	  v16,v14,v15;		    \

-	vcmpequb. v0,v16,v18;		    \

+	vcmpequb. v0,v16,VREG_ZERO;	    \

 	bne	  cr6,L(label)

-#define TAIL(vreg,increment)	   \

-	vctzlsbb  r4,vreg;	   \

-	subf	  r3,r3,r5;	   \

-	addi	  r4,r4,increment; \

-	add	  r3,r3,r4;	   \

-	blr

-

 /* Implements the function

    int [r3] strlen (const void *s [r3])

+   but when USE_AS_RAWMEMCHR is set, implements the function

+

+   void* [r3] rawmemchr (const void *s [r3], int c [r4])

+

    The implementation can load bytes past a matching byte, but only

    up to the next 64B boundary, so it never crosses a page.  */

 .machine power9

-ENTRY_TOCLESS (STRLEN, 4)

-	CALL_MCOUNT 1

+ENTRY_TOCLESS (FUNCNAME, 4)

+	CALL_MCOUNT MCOUNT_NARGS

-	vspltisb  v18,0

+#ifdef USE_AS_RAWMEMCHR

+	xori	r5,r4,0xff

+

+	mtvsrd	v18+32,r4	/* matching char in v18  */

+	mtvsrd	v19+32,r5	/* non matching char in v19  */

+

+	vspltb	v18,v18,7	/* replicate  */

+	vspltb	v19,v19,7	/* replicate  */

+#else

 	vspltisb  v19,-1

+#endif

+	vspltisb  VREG_ZERO,0

 	/* Next 16B-aligned address. Prepare address for L(aligned).  */

 	addi	  r5,r3,16

@@ -90,16 +138,25 @@ ENTRY_TOCLESS (STRLEN, 4)

 	vcmpequb. v6,v0,v18

 	beq	  cr6,L(aligned)

+#ifdef USE_AS_RAWMEMCHR

+	vctzlsbb  r6,v6

+	add	  r3,r3,r6

+#else

 	vctzlsbb  r3,v6

+#endif

 	blr

-	/* Test next 176B, 16B at a time.  The main loop is optimized for longer

-	   strings, so checking the first bytes in 16B chunks benefits a lot

-	   small strings.  */

+	/* Test up to OFF_START_LOOP-16 bytes in 16B chunks.  The main loop is

+	   optimized for longer strings, so checking the first bytes in 16B

+	   chunks benefits a lot small strings.  */

 	.p2align 5

 L(aligned):

+#ifdef USE_AS_RAWMEMCHR

+	cmpdi	cr5,r4,0	/* Check if c == 0.  This will be useful to

+				  choose how we will perform the main loop.  */

+#endif

 	/* Prepare address for the loop.  */

-	addi	  r4,r3,192

+	addi	  r4,r3,OFF_START_LOOP

 	clrrdi	  r4,r4,6

 	CHECK16(v0,0,r5,tail1)

@@ -113,15 +170,43 @@ L(aligned):

 	CHECK16(v8,128,r5,tail9)

 	CHECK16(v9,144,r5,tail10)

 	CHECK16(v10,160,r5,tail11)

+#ifdef USE_AS_RAWMEMCHR

+	CHECK16(v0,176,r5,tail12)

+	CHECK16(v1,192,r5,tail13)

+	CHECK16(v2,208,r5,tail14)

+	CHECK16(v3,224,r5,tail15)

+#endif

 	addi	  r5,r4,128

+#ifdef USE_AS_RAWMEMCHR

+	/* If c == 0, use the same loop as strlen, without the vsububm.  */

+	beq	cr5,L(loop)

+

+	/* This is very similar to the block after L(loop), the difference is

+	   that here RAWMEMCHR_SUBTRACT_VECTORS is not empty, and we subtract

+	   each byte loaded by the char we are looking for, this way we can keep

+	   using vminub to merge the results and checking for nulls.  */

+	.p2align 5

+L(rawmemchr_loop):

+	CHECK64(0,r4,pre_tail_64b)

+	CHECK64(64,r4,pre_tail_64b)

+	addi	  r4,r4,256

+

+	CHECK64(0,r5,tail_64b)

+	CHECK64(64,r5,tail_64b)

+	addi	  r5,r5,256

+

+	b	  L(rawmemchr_loop)

+#endif

 	/* Switch to a more aggressive approach checking 64B each time.  Use 2

 	   pointers 128B apart and unroll the loop once to make the pointer

 	   updates and usages separated enough to avoid stalls waiting for

 	   address calculation.  */

 	.p2align 5

 L(loop):

+#undef RAWMEMCHR_SUBTRACT_VECTORS

+#define RAWMEMCHR_SUBTRACT_VECTORS /* nothing */

 	CHECK64(0,r4,pre_tail_64b)

 	CHECK64(64,r4,pre_tail_64b)

 	addi	  r4,r4,256

@@ -140,10 +225,10 @@ L(tail_64b):

 	   block and mark it in its corresponding VR.  lxvp vx,0(ry) puts the

 	   low 16B bytes into vx+1, and the high into vx, so the order here is

 	   v5, v4, v7, v6.  */

-	vcmpequb  v1,v5,v18

-	vcmpequb  v2,v4,v18

-	vcmpequb  v3,v7,v18

-	vcmpequb  v4,v6,v18

+	vcmpequb  v1,v5,VREG_ZERO

+	vcmpequb  v2,v4,VREG_ZERO

+	vcmpequb  v3,v7,VREG_ZERO

+	vcmpequb  v4,v6,VREG_ZERO

 	/* Take into account the other 64B blocks we had already checked.  */

 	add	r5,r5,r6

@@ -165,7 +250,9 @@ L(tail_64b):

 	or	  r10,r8,r7

 	cnttzd	  r0,r10	  /* Count trailing zeros before the match.  */

+#ifndef USE_AS_RAWMEMCHR

 	subf	  r5,r3,r5

+#endif

 	add	  r3,r5,r0	  /* Compute final length.  */

 	blr

@@ -213,9 +300,32 @@ L(tail10):

 L(tail11):

 	TAIL(v10,160)

-END (STRLEN)

+#ifdef USE_AS_RAWMEMCHR

+	.p2align  5

+L(tail12):

+	TAIL(v0,176)

+

+	.p2align  5

+L(tail13):

+	TAIL(v1,192)

+

+	.p2align  5

+L(tail14):

+	TAIL(v2,208)

+

+	.p2align  5

+L(tail15):

+	TAIL(v3,224)

+#endif

+

+END (FUNCNAME)

-#ifdef DEFINE_STRLEN_HIDDEN_DEF

+#ifdef USE_AS_RAWMEMCHR

+weak_alias (__rawmemchr,rawmemchr)

+libc_hidden_builtin_def (__rawmemchr)

+#else

+# ifdef DEFINE_STRLEN_HIDDEN_DEF

 weak_alias (__strlen, strlen)

 libc_hidden_builtin_def (strlen)

+# endif

 #endif

diff --git a/sysdeps/powerpc/powerpc64/multiarch/Makefile b/sysdeps/powerpc/powerpc64/multiarch/Makefile

index 1d517698429e1230..ac2446aca62cc4ab 100644

--- a/sysdeps/powerpc/powerpc64/multiarch/Makefile

+++ b/sysdeps/powerpc/powerpc64/multiarch/Makefile

@@ -33,9 +33,9 @@ sysdep_routines += memcpy-power8-cached memcpy-power7 memcpy-a2 memcpy-power6 \

 ifneq (,$(filter %le,$(config-machine)))

 sysdep_routines += memcpy-power10 memmove-power10 memset-power10 \

+		   rawmemchr-power9 rawmemchr-power10 \

 		   strcmp-power9 strncmp-power9 strcpy-power9 stpcpy-power9 \

-		   rawmemchr-power9 strlen-power9 strncpy-power9 stpncpy-power9 \

-		   strlen-power10

+		   strlen-power9 strncpy-power9 stpncpy-power9 strlen-power10

 endif

 CFLAGS-strncase-power7.c += -mcpu=power7 -funroll-loops

 CFLAGS-strncase_l-power7.c += -mcpu=power7 -funroll-loops

diff --git a/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c b/sysdeps/powerpc/powerpc64/multiarch/ifunc-impl-list.c

index 6e36659d1903448a..127af84b32a8196f 100644

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

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

@@ -257,6 +257,10 @@ __libc_ifunc_impl_list (const char *name, struct libc_ifunc_impl *array,

   /* Support sysdeps/powerpc/powerpc64/multiarch/rawmemchr.c.  */

   IFUNC_IMPL (i, name, rawmemchr,

 #ifdef __LITTLE_ENDIAN__

+	      IFUNC_IMPL_ADD (array, i, rawmemchr,

+			      (hwcap2 & PPC_FEATURE2_ARCH_3_1)

+                              && (hwcap & PPC_FEATURE_HAS_VSX),

+                              __rawmemchr_power10)

 	      IFUNC_IMPL_ADD (array, i, rawmemchr,

 			      hwcap2 & PPC_FEATURE2_ARCH_3_00,

 			      __rawmemchr_power9)

diff --git a/sysdeps/powerpc/powerpc64/multiarch/rawmemchr-power10.S b/sysdeps/powerpc/powerpc64/multiarch/rawmemchr-power10.S

new file mode 100644

index 0000000000000000..bf1ed7e1941f922d

--- /dev/null

+++ b/sysdeps/powerpc/powerpc64/multiarch/rawmemchr-power10.S

@@ -0,0 +1,21 @@

+/* Optimized rawmemchr implementation for PowerPC64/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 RAWMEMCHR __rawmemchr_power10

+

+#include <sysdeps/powerpc/powerpc64/le/power10/rawmemchr.S>

diff --git a/sysdeps/powerpc/powerpc64/multiarch/rawmemchr.c b/sysdeps/powerpc/powerpc64/multiarch/rawmemchr.c

index 2a7ae5a1ed02e556..369d6359e8987052 100644

--- a/sysdeps/powerpc/powerpc64/multiarch/rawmemchr.c

+++ b/sysdeps/powerpc/powerpc64/multiarch/rawmemchr.c

@@ -26,6 +26,7 @@ extern __typeof (__rawmemchr) __rawmemchr_ppc attribute_hidden;

 extern __typeof (__rawmemchr) __rawmemchr_power7 attribute_hidden;

 # ifdef __LITTLE_ENDIAN__

 extern __typeof (__rawmemchr) __rawmemchr_power9 attribute_hidden;

+extern __typeof (__rawmemchr) __rawmemchr_power10 attribute_hidden;

 # endif

 # undef __rawmemchr

@@ -34,6 +35,9 @@ extern __typeof (__rawmemchr) __rawmemchr_power9 attribute_hidden;

    ifunc symbol properly.  */

 libc_ifunc_redirected (__redirect___rawmemchr, __rawmemchr,

 # ifdef __LITTLE_ENDIAN__

+		     (hwcap2 & PPC_FEATURE2_ARCH_3_1)

+		     && (hwcap & PPC_FEATURE_HAS_VSX)

+		     ? __rawmemchr_power10 :

 		       (hwcap2 & PPC_FEATURE2_ARCH_3_00)

 		       ? __rawmemchr_power9 :

 # endif