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[PATCH] powerpc: Handle worstcase behavior in strstr() for POWER7
- From: Rajalakshmi Srinivasaraghavan <raji at linux dot vnet dot ibm dot com>
- To: libc-alpha at sourceware dot org
- Cc: sjmunroe at us dot ibm dot com, Rajalakshmi Srinivasaraghavan <raji at linux dot vnet dot ibm dot com>
- Date: Tue, 18 Aug 2015 22:40:56 +0530
- Subject: [PATCH] powerpc: Handle worstcase behavior in strstr() for POWER7
- Authentication-results: sourceware.org; auth=none
Instead of checking needle length, constant 'n' number of comparisons
is checked to fall back to default implementation. This patch is tested
on powerpc64 and powerpc64le.
2015-08-18 Rajalakshmi Srinivasaraghavan <raji@linux.vnet.ibm.com>
* sysdeps/powerpc/powerpc64/power7/strstr.S: Handle worst case.
---
sysdeps/powerpc/powerpc64/power7/strstr.S | 22 +++++++++++++++-------
1 file changed, 15 insertions(+), 7 deletions(-)
diff --git a/sysdeps/powerpc/powerpc64/power7/strstr.S b/sysdeps/powerpc/powerpc64/power7/strstr.S
index bfb0c49..fb3c810 100644
--- a/sysdeps/powerpc/powerpc64/power7/strstr.S
+++ b/sysdeps/powerpc/powerpc64/power7/strstr.S
@@ -23,6 +23,8 @@
/* The performance gain is obtained using aligned memory access, load
* doubleword and usage of cmpb instruction for quicker comparison. */
+#define ITERATIONS 64
+
#ifndef STRLEN
/* For builds with no IFUNC support, local calls should be made to internal
GLIBC symbol (created by libc_hidden_builtin_def). */
@@ -62,6 +64,8 @@ EALIGN (strstr, 4, 0)
cfi_offset(r30, -16)
std r29, -24(r1) /* Save callers register r29. */
cfi_offset(r29, -24)
+ std r28, -32(r1) /* Save callers register r28. */
+ cfi_offset(r28, -32)
std r0, 16(r1) /* Store the link register. */
cfi_offset(lr, 16)
stdu r1, -FRAMESIZE(r1) /* Create the stack frame. */
@@ -69,7 +73,6 @@ EALIGN (strstr, 4, 0)
dcbt 0, r3
dcbt 0, r4
-
cmpdi cr7, r3, 0
beq cr7, L(retnull)
cmpdi cr7, r4, 0
@@ -84,10 +87,6 @@ EALIGN (strstr, 4, 0)
cmpdi cr7, r3, 0 /* If search str is null. */
beq cr7, L(ret_r3)
- /* Call __strstr_ppc if needle len > 2048 */
- cmpdi cr7, r3, 2048
- bgt cr7, L(default)
-
mr r31, r3
mr r4, r3
mr r3, r29
@@ -105,7 +104,8 @@ EALIGN (strstr, 4, 0)
/* If first char of search str is not present. */
cmpdi cr7, r3, 0
ble cr7, L(end)
-
+ /* Reg r28 is used to count the number of iterations. */
+ li r28, 0
rldicl r8, r3, 0, 52 /* Page cross check. */
cmpldi cr7, r8, 4096-16
bgt cr7, L(bytebybyte)
@@ -324,6 +324,10 @@ L(return4):
.align 4
L(begin):
mr r3, r8
+ /* When our iterations exceed ITERATIONS,fall back to default. */
+ addi r28, r28, 1
+ cmpdi cr7, r28, ITERATIONS
+ beq cr7, L(default)
lbz r4, 0(r30)
bl STRCHR
nop
@@ -423,6 +427,10 @@ L(nextbyte):
cmpdi cr7, r9, -1
beq cr7, L(end)
addi r3, r4, 1
+ /* When our iterations exceed ITERATIONS,fall back to default. */
+ addi r28, r28, 1
+ cmpdi cr7, r28, ITERATIONS
+ beq cr7, L(default)
lbz r4, 0(r30)
bl STRCHR
nop
@@ -490,7 +498,6 @@ L(retnull):
.align 4
L(default):
- mr r3, r29
mr r4, r30
bl __strstr_ppc
nop
@@ -500,6 +507,7 @@ L(end):
addi r1, r1, FRAMESIZE /* Restore stack pointer. */
cfi_adjust_cfa_offset(-FRAMESIZE)
ld r0, 16(r1) /* Restore the saved link register. */
+ ld r28, -32(r1) /* Restore callers save register r28. */
ld r29, -24(r1) /* Restore callers save register r29. */
ld r30, -16(r1) /* Restore callers save register r30. */
ld r31, -8(r1) /* Restore callers save register r31. */
--
1.8.3.1