powerpc/lib: optimise PPC32 memcmp

At the time being, memcmp() compares two chunks of memory
byte per byte.

This patch optimises the comparison by comparing word by word.

On the same way as commit 15c2d45d17418 ("powerpc: Add 64bit
optimised memcmp"), this patch moves memcmp() into a dedicated
file named memcmp_32.S

A small benchmark performed on an 8xx comparing two chuncks
of 512 bytes performed 100000 times gives:

Before : 5852274 TB ticks
After:   1488638 TB ticks

This is almost 4 times faster

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>

diff --git a/arch/powerpc/lib/Makefile b/arch/powerpc/lib/Makefile
index 2c9b8c0adf229bc0d224cc9781ba58aad7747385..d0ca13ad823105b7401d564a6f13faddcafe3023 100644 (file)
--- a/arch/powerpc/lib/Makefile
+++ b/arch/powerpc/lib/Makefile
@@ -26,14 +26,14 @@ obj-$(CONFIG_PPC_BOOK3S_64) += copyuser_power7.o copypage_power7.o \
                               memcpy_power7.o
 
 obj64-y        += copypage_64.o copyuser_64.o mem_64.o hweight_64.o \
-          memcpy_64.o memcmp_64.o pmem.o
+          memcpy_64.o pmem.o
 
 obj64-$(CONFIG_SMP)    += locks.o
 obj64-$(CONFIG_ALTIVEC)        += vmx-helper.o
 obj64-$(CONFIG_KPROBES_SANITY_TEST) += test_emulate_step.o
 
 obj-y                  += checksum_$(BITS).o checksum_wrappers.o \
-                          string_$(BITS).o
+                          string_$(BITS).o memcmp_$(BITS).o
 
 obj-y                  += sstep.o ldstfp.o quad.o
 obj64-y                        += quad.o

diff --git a/arch/powerpc/lib/memcmp_32.S b/arch/powerpc/lib/memcmp_32.S
new file mode 100644 (file)
index 0000000..5010e37
--- /dev/null
+++ b/arch/powerpc/lib/memcmp_32.S
@@ -0,0 +1,45 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+
+/*
+ * memcmp for PowerPC32
+ *
+ * Copyright (C) 1996 Paul Mackerras.
+ *
+ */
+
+#include <asm/ppc_asm.h>
+#include <asm/export.h>
+
+       .text
+
+_GLOBAL(memcmp)
+       srawi.  r7, r5, 2               /* Divide len by 4 */
+       mr      r6, r3
+       beq-    3f
+       mtctr   r7
+       li      r7, 0
+1:     lwzx    r3, r6, r7
+       lwzx    r0, r4, r7
+       addi    r7, r7, 4
+       cmplw   cr0, r3, r0
+       bdnzt   eq, 1b
+       bne     5f
+3:     andi.   r3, r5, 3
+       beqlr
+       cmplwi  cr1, r3, 2
+       blt-    cr1, 4f
+       lhzx    r3, r6, r7
+       lhzx    r0, r4, r7
+       addi    r7, r7, 2
+       subf.   r3, r0, r3
+       beqlr   cr1
+       bnelr
+4:     lbzx    r3, r6, r7
+       lbzx    r0, r4, r7
+       subf.   r3, r0, r3
+       blr
+5:     li      r3, 1
+       bgtlr
+       li      r3, -1
+       blr
+EXPORT_SYMBOL(memcmp)

diff --git a/arch/powerpc/lib/string.S b/arch/powerpc/lib/string.S
index 5343a88e619e9d97f162d7cf8c6943d50fad38e9..4b41970e9ed84bac330c0f7f2b5a23c10960c381 100644 (file)
--- a/arch/powerpc/lib/string.S
+++ b/arch/powerpc/lib/string.S
@@ -54,23 +54,6 @@ _GLOBAL(strncmp)
        blr
 EXPORT_SYMBOL(strncmp)
 
-#ifdef CONFIG_PPC32
-_GLOBAL(memcmp)
-       PPC_LCMPI 0,r5,0
-       beq-    2f
-       mtctr   r5
-       addi    r6,r3,-1
-       addi    r4,r4,-1
-1:     lbzu    r3,1(r6)
-       lbzu    r0,1(r4)
-       subf.   r3,r0,r3
-       bdnzt   2,1b
-       blr
-2:     li      r3,0
-       blr
-EXPORT_SYMBOL(memcmp)
-#endif
-
 _GLOBAL(memchr)
        PPC_LCMPI 0,r5,0
        beq-    2f